Prevalences of dementia and cognitive impairment among older people in sub-Saharan Africa: a systematic review

Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422 Systematic reviews 773 Prevalences of dementia and cognitive impairment among older people in sub-Saharan Africa: a systematic review Angelique Mavrodaris,a John Powellb & Margaret Thorogoodc Introduction The prevalence of age-related health problems is becoming an important public health concern as proportions of older individuals in populations worldwide grow.1 Dementia is one of the major causes of disability in older people.2 It is a complex syndrome characterized by global and irreversible cognitive decline that is severe enough to undermine daily functioning.3 Dementia is a chronic illness that arises from an interplay of genetic, environmental and behavioural factors, with severe adverse influences on social and physical activities and quality of life. In cognitive impairment and mild cognitive impair- ment, the cognitive deficit is less severe than in dementia and normal daily function and independence are generally maintained. It is a chronic condition that is a precursor to dementia in up to one third of cases.3 Cognitive impairment and dementia are increasing globally and are predicted to increase proportionately more in developing regions.1,4–6 Projections indicate that by 2050 the number of individuals older than 60 years will be ap- proximately 2 billion and will account for 22% of the world’s population. Four fifths of the people older than 60 years will be living in developing countries in Africa, Asia or Latin America.7 It is estimated that 35.6 million people are currently living with dementia worldwide and that the number will nearly double every 20 years, reaching 115.4 million in 2050, with the majority living in developing countries.8 Of the total number of people with dementia worldwide, 57.7% lived in developing countries in 2010 and a proportionate increase to 70.5% by 2050 is anticipated.8 Consequently, the health and social burden of cognitive impairment and dementia will rise dramatically in these regions.9 Developing countries, includ- ing those in sub-Saharan Africa, are currently undergoing a demographic and epidemiological transition and the impact of population ageing in sub-Saharan Africa will increasingly augment the burden of noncommunicable and degenerative diseases in this region. Few studies to determine the prevalence of dementia have been conducted in sub-Saharan Africa.10,11 Early studies12 showed a lower prevalence than in Europe11,13 and the United States of America, where approximately 6.2% and 8%, respec- tively, of people aged 65 years or older are reported to have dementia.14–16 The aim of this study was to perform a systematic review of the literature to obtain the best available estimates of the prevalences of cognitive impairment and dementia in sub-Saharan Africa and to identify gaps in current research. Methods A systematic review of studies reporting the prevalences of de- mentia and cognitive impairment among older black Africans in sub-Saharan Africa countries was conducted according to Preferred Reporting Items for Systematic Reviews and Meta- Analyses (PRISMA) guidelines.17 Search strategy We searched the following databases between February and May 2011: PubMed (search range, 1950 to week 18 of 2011); the Web of Knowledge, which includes the Web of Science Conference Proceedings Citation Index (1970 to week 18 of 2011), the BIOSIS Citation Index (1969 to week 18 of 2011), Journal Citation Reports (1997–2008) and CAB Abstracts Objective To perform a systematic review of the literature on the prevalence of cognitive impairment and dementia in sub-Saharan Africa. Methods Five electronic databases were searched for relevant abstracts and to identify papers eligible for full-text review. A study was included if two authors agreed that it had a cohort, case–control or cross-sectional design and reported population-level data; was limited to black African adults older than 50 years or described as “elderly” or “old”; reported data for individuals residing in sub-Saharan Africa; and reported at least one measure of cognitive impairment or clinical outcomes relevant to cognitive decline. References of papers included in our study were searched to identify additional candidate publications. Disagreements about inclusion were adjudicated during discussions involving all authors. Data were extracted independently by two authors, using a form developed by the authors and tested on a sample of papers. Findings A total of 2320 unique papers was found; the full text of 87 was reviewed. Nineteen papers featuring 11 cross-sectional studies were included; all were published during 1995–2011. Studies occurred in Benin, Botswana, the Central African Republic, the Congo and Nigeria and enrolled approximately 10 500 participants. The prevalence of dementia ranged from 0%, in Nigeria, to 10.1% (95% confidence interval, CI: 8.6–11.8), also in Nigeria. The prevalence of cognitive impairment ranged from 6.3%, in Nigeria, to 25% (95% CI: 21.2–29.0), in the Central African Republic. Conclusion Prevalences of dementia and cognitive impairment in sub-Saharan Africa varied widely, with few published studies revealed by the literature search. a Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, CV4 7A, England. b University of Oxford, Oxford, England. c University of the Witwatersrand, Johannesburg, South Africa. Correspondence to Angelique Mavrodaris (e-mail: A.Mavrodaris@warwick.ac.uk). (Submitted: 15 February 2013 – Revised version received: 21 June 2013 – Accepted: 22 June 2013 – Published online: 20 August 2013 ) Systematic revi s Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422774 Systematic reviews Dementia and cognitive impairment in sub-Saharan Africa Angelique Mavrodaris et al. (1973 to week 18 of 2011); EMBASE (1947 to week 18 of 2011); ASSIA (1987 to week 18 of 2011) and PsycNET (1894 to week 18 of 2011). The search terms used included variations across the following broad terms: epidemiology, prevalence, incidence, cognition, cogni- tive impairment, dementia, Alzheimer disease, sub-Saharan Africa, names of individual sub-Saharan African coun- tries, elderly and older people. Searches incorporated MeSH (medical subject heading) terms or equivalents, exploded terms and text word terms (Appendix A, available at: http://www2.warwick. ac.uk/fac/med/research/hscience/re- search/dementia/). We checked the reference lists of retrieved articles for further relevant studies. Study selection Studies were included if they satisfied all of the following criteria: (i) the study had a cohort, case–control or cross- sectional study design and reported population-level data, defined as data from population surveys or patients identified in primary or community care samples; (ii) the study was limited to black African adults who were older than 50 years or described as “elderly” or “old” or, if the age range of subjects was broader, reported data separately for those older than 50 years; (iii) the study population resided in sub-Saharan Afri- ca or, if the geographic area of residence was broader, reported data separately for those residing in sub-Saharan Africa; and (iv) the study reported at least one measure of cognitive impairment or clinical outcomes relevant to cognitive decline (i.e. dementia, Alzheimer dis- ease, amnesia and/or confusion) and at least one measure of the frequency of cognitive impairment (i.e. prevalence and/or incidence). No language restrictions were ap- plied. All titles identified were screened independently for potential relevance by at least two authors and abstracts were obtained if the title was considered relevant by at least one author. Abstracts were screened in the same way. Finally, full texts of the remaining papers were assessed for eligibility and when two authors disagreed on inclusion a deci- sion was made in discussion by all three authors. Data extraction and analysis Data were extracted from each paper independently by two authors, using a data collection form developed by the authors and tested on a sample of papers (Appendix B, available at: http://www2.warwick.ac.uk/fac/med/ research/hscience/research/dementia/). Details about the study design, partici- pant characteristics, analysis methods and findings, and authors’ conclusions were entered into the form. For studies in which several related papers were identified, the papers were evaluated collectively as one study for data extraction.12,15,16,18–23 In one paper, two studies were reported, and we considered these studies separately.24 Because of considerable heterogeneity in methods (sampling and study design), population samples (age, health, socio- economic status, geographical region and cultural background) and screen- ing or diagnostic measures, we did not pool the data but report our findings in narrative form. Two authors independently evalu- ated the quality of the studies, using a standardized checklist. The following factors were assessed: whether the sample was representative of the target population, whether screening and diagnostic tools produced reliable and valid measures of psychiatric outcome and key concepts and whether the analysis accounted for special features of the sampling design and included confidence intervals.25 Results Study characteristics We retrieved 281 references from PubMed, 1081 from the Web of Knowl- edge, 55 from CAB Abstracts, 1192 from EMBASE, 43 from ASSIA and 4 from PsycNET. After removal of duplicates, 2320 references remained. Initial screen- ing yielded 86 papers for full-text review and one additional reference was iden- tified from searching reference lists of included papers. (Fig. 1). One additional reference was identified while searching reference lists of included papers. Our systematic review yielded 19 papers as- sociated with 11 studies. The studies reported findings for 10 413 participants. All studies were cross-sectional and were published between 1995 and 2011, with approxi- mately two thirds published between 2005 and 2011 (Table 1). The studies were conducted in Benin, Botswana, the Central African Republic, the Congo and Nigeria; most occurred in Nigeria, in Ibadan, Dunukofia, Jos, Uwan and Zaria. Five studies included participants from both rural and urban settings, one study included only urban par- ticipants and five studies included only rural participants. All studies included participants aged 65 years and older; two studies also included participants Fig. 1. Flow diagram for a systematic review of the literature to select studies evaluating the prevalences of dementia and cognitive impairment in sub- Saharan Africa Articles excluded (n = 68) Reasons: (i) No relevance to sub-Saharan Africa (n = 25) (ii) No frequency measure reported (n = 16) (iii) Participants aged < 50 years (n = 20) (iv) No formal screening tool used (n = 1) (v) Mixed ethnicities among participants (n = 2) (vi) Unclear diagnosis (n = 1) (vii) Hospital data used (n = 1) (viii) Not a population sample (n = 2) Records identified through database searching to March 2011 (n = 2656) Records after duplicates removed (n = 2320) Records screened (n = 2320) Records excluded (n = 2234) Full-text articles assessed for eligibility (n = 86) Additional article identified from reference lists (n = 1) 19 papers related to 11 studies were included Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422 775 Systematic reviews Dementia and cognitive impairment in sub-Saharan AfricaAngelique Mavrodaris et al. Ta bl e 1. Ch ar ac te ris tic s o f t he st ud ie s o bt ai ne d fr om a sy st em at ic re vi ew o f t he li te ra tu re o n th e pr ev al en ce s o f d em en tia a nd co gn iti ve im pa irm en t i n su b- Sa ha ra n Af ric a Co un tr y, re fe re nc e Pu bl ica tio n da te St ud y s ite Pa rt ici pa nt s Pr ev al en ce o f d em en tia , % (9 5% CI ) Pr ev al en ce o f c og ni tiv e im pa irm en t, % (9 5% CI ) Ar ea Se tt in g No . Ag e in ye ar s Ov er al l By a ge in ye ar s Ov er al l By a ge in ye ar s Be ni n Gu er ch et e t a l.2 6 20 09 D jid ja Ru ra l 50 2 ≥ 6 5 2. 6 (1 .1 –3 .8 ) 65 –7 9: 1 .1 (0 .3 –2 .9 ) 10 .4 (7 .7 –1 3. 1) a 65 –7 9: 6 .5 (3 .9 –9 .1 ) ≥ 8 0: 6 .0 (2 .8 –1 1. 1) ≥ 8 0: 2 6. 6 (1 9. 5– 33 .7 ) Bo ts w an a Cl au se n et a l.2 7 20 05 N at io n- w id e Ru ra l a nd ur ba n 37 2 ≥ 6 0 – – 9. 0 60 –6 9: 4 .0 70 –7 9: 9 .0 ≥ 8 0: 2 0. 0 Ce nt ra l A fr ic an Re pu bl ic Gu er ch et e t a l.2 4 20 10 Ba ng ui Ru ra l 49 6 ≥ 6 5 8. 1 (5 .8 –1 0. 8) 65 –7 4: 5 .4 (3 .0 –7 .8 ) 25 (2 1. 2– 29 .0 )a 65 –7 4: 2 6. 3 (2 1. 7– 31 .4 ) 75 –8 4: 1 1. 6 (6 .7 –1 8. 1) 75 –8 4: 2 0. 3 (1 3. 9– 28 .0 ) ≥ 8 5: 2 5. 0 (7 .7 –4 2. 3) ≥ 8 5: 3 3. 3 (1 5. 6– 55 .3 ) Co ng o Gu er ch et e t a l.2 4 20 10 Br az za vi lle U rb an 52 0 ≥ 6 5 6. 7 (4 .7 –9 .2 ) 65 –7 4: 4 .4 (2 .3 –7 .5 ) 18 .8 (1 5. 6– 22 .5 )a 65 –7 4: 1 1. 3 (7 .8 –1 5. 7) 75 –8 4: 7 .4 (4 .2 –1 1. 9) 75 –8 4: 2 7. 1 (2 1. 1– 33 .8 ) ≥ 8 5: 1 8. 6 (8 .4 –3 3. 4) ≥ 8 5: 2 7. 9 (1 5. 3– 43 .7 ) N ig er ia Yu su f e t a l.2 8 20 11 Za ria Ru ra l 32 2 ≥ 6 5 2. 8 (1 .0 –4 .5 8) 65 –7 9: 2 .0 (1 .0 4– 2. 96 ) – – U w ak w e et a l.2 9 20 09 D un uk ofi a Ru ra l 91 4 ≥ 6 5 – – 11 .8 a nd 9 .9 b – Gu re je e t a l.3 0 20 06 Ib ad an Ru ra l a nd ur ba n 19 04 ≥ 6 5 10 .1 (8 .6 –1 1. 8) 65 –6 9: 7 .2 (5 .5 –9 .4 ) – – 70 –7 4: 7 .7 (4 .7 –1 2. 2) 75 –7 9: 1 0. 7 (7 .3 –1 5. 4) ≥ 8 0: 2 0. 9 (1 6. 7– 26 .0 ) O ch ay i e t a l.3 1 20 06 Jo s Ru ra l a nd ur ba n 28 0 ≥ 6 5 6. 4 (3 .8 –9 .9 ) 65 –7 4: 5 .2 – – 75 –8 4: 5 .9 85 –9 4: 1 4. 0 ≥ 9 5: 1 2 Ba iy ew u et a l.3 2 20 02 Ib ad an Ru ra l a nd ur ba n 24 87 ≥ 6 5 – – 6. 3a – U w ak w e3 3 20 00 U w an Ru ra l 16 4 ≥ 6 0 0c – – – O gu nn iy i e t a l. a nd ot he rs 12 ,1 5, 16 ,1 8– 23 19 95 –2 00 6 Ib ad an Ru ra l a nd ur ba n 24 94 ≥ 6 5 2. 3 (1 .1 7– 3. 41 ) 65 –7 4: 0 .8 6 – – 75 –8 4: 2 .7 2 ≥ 8 5: 9 .5 9 CI , c on fid en ce in te rv al . a D at a ar e fo r c og ni tiv e im pa irm en t w ith n o de m en tia . b D at a ar e fo r p ar tic ip an ts w ith im pa irm en t d et ec te d by 1 m em or y te st a nd ≥ 2 te st s, re sp ec tiv el y. c Th irt y- fo ur (2 0. 75 % ) w er e fo rg et fu l. N ot e: In a ll 11 st ud ie s i nc re as in g ag e w as a ss oc ia te d w ith a n in cr ea sin g pr ev al en ce o f b ot h de m en tia a nd c og ni tiv e im pa irm en t. Fi ve st ud ie s f ou nd a h ig he r p re va le nc e of d em en tia in w om en .12 ,2 4, 30 ,3 1 Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422776 Systematic reviews Dementia and cognitive impairment in sub-Saharan Africa Angelique Mavrodaris et al. aged 60–64 years. The mean age of the participants ranged between 72.0 and 76.1 years. All studies included both female and male participants and 10 studies reported prevalence data strati- fied by sex. Three studies reported the preva- lences of both cognitive impairment and dementia, with data for 1518 participants analysed.24,26 Five stud- ies reported only the prevalence of dementia12,15,16,18–23,28,30,31,33 and three reported only the prevalence of cogni- tive impairment, with data for 5164 and 4097 participants, respectively, analysed.27,29,32 Table 2 shows the cognitive screen- ing tools and diagnostic processes used in the studies and indicators of the methodological quality are shown in Table 3. Only three studies documented evidence that confirmed the reliability of the tools.12,15,16,18–23,30,32 Three stud- ies did not report confidence intervals (or information necessary to calculate them)27,29,32 and one did not report a confidence interval but provided enough information for this to be calculated.33 One study did not document sufficient information regarding appropriate probability sampling.29 One study docu- mented uncertainties regarding cultural validity of the screening tools.27 Dementia prevalence Benin A study from Djidja, a rural area, in- cluded 502 participants and reported a prevalence of 2.6% (Table 1).26 The Community Screening Interview for Dementia (CSI-D) was used for de- tection of dementia. Diagnosis was confirmed by clinical assessment and participant-based interview; clinical dementia was diagnosed according to DSM-IV criteria and probable or pos- sible Alzheimer disease was based on National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer Disease and Related Disorders Association II (NINCDS- ADRDA II) criteria. Analysis on the basis of dementia subtype revealed that the prevalence of Alzheimer disease was 2.2% and accounted for 53.8% of dementia diagnoses in this population, while vascular dementia contributed 7.7%. A further 30% of dementia cases were documented as possible dementia. Central African Republic and Congo The dementia prevalence was 8.1% among 496 participants in a rural region of Bangui, Central African Republic, and 6.7% among 520 participants from an urban region in Brazzaville, Congo.24 Cognitive screening was performed us- ing the CSI-D and 5-Word Test, adapted and presented in local languages. Di- agnosis was confirmed by neurological examination and further psychometric testing in participants suspected of dementia (defined as a CSI-D score of < 25.5 of 30 or a 5-Word Test score of < 10 of 10). Both studies measured the preva- lence of dementia subtypes. According to findings of neurological examina- tions, 82.5% of participants with demen- tia in Bangui had probable Alzheimer disease and 17.5% had vascular demen- tia, while in Brazzaville the proportions were 68.6% and 31.4%, respectively. Nigeria Five studies reported prevalence data for dementia. A small study of 322 partici- pants conducted in rural Zaria used a battery of cognitive tests similar to that used in the 1995 study from Ibadan de- scribed below and reported a prevalence of 2.8%.28 Two studies from Ibadan were of a similar size but conducted approxi- mately 10 years apart. These reported prevalences of 2.3% in 1995 and 10.1% in 2006. Differences between the stud- ies included use of a single validated screening tool, the adapted 10-Word Delay Recall Test (10-WDRT), to define probable dementia in the 2006 study30 and a combination of screening tools (including the 10-WDRT) and clinical assessment, to define dementia in the 1995 study.12,15,16,18–23 The 2006 study also covered a wider region, including rural areas, while the earlier study was conducted in an inner-city region. A study from Jos, in central Nigeria, reported a prevalence of 6.4% among 280 participants.31 This study used the CSI-D but there was no clinical assess- ment to confirm the diagnosis. A small study of 164 participants aged 60 years or older conducted in Uwan described common mental disorders. No cases of dementia were found. This study used the Self-Reporting Questionnaire (SRQ-24) and the Geriatric Mental State Schedule (GMS) as screening tools but the GMS had not been validated in Nigeria.33 Two studies examined subtypes of dementia. Yusuf et al. confirmed clinical cases of dementia based on the fulfilment of diagnostic criteria in both the International classification of diseases, tenth revision (ICD-10), and the Diagnostic and statistical manual of mental disorders, fourth revision (DSM- IV). DSM-IV criteria were then used to diagnose Alzheimer disease and ICD-10 criteria were used to diagnose vascular dementia.28 Clinical criteria were used to diagnose other subtypes. The prevalence of Alzheimer disease was 1.9%, which accounted for six of the nine partici- pants with dementia; of the remaining three, two had vascular dementia and one had fronto-temporal dementia. Among patients with dementia in the study from Ibadan, Alzheimer disease was diagnosed in 64.3% and vascular dementia was diagnosed in 28.6%.12 Clinical diagnoses were confirmed using DSM-IV, ICD-10 and clinical criteria developed by the NINCDS-ADRDA II. Cognitive impairment prevalence Benin In a study of 502 participants in the rural community of Djidja, researchers adapted the cognitive section of the CSI-D to allow for a lack of temporal orientation and a high rate of illiteracy, such that a score of 30 (rather than 33) was the highest possible (Table 1). The researchers also had considerable dif- ficulties in identifying informants to complete the informant section of the CSI-D and therefore adapted the criteria for cognitive impairment. Cognitive impairment was defined as a poor per- formance in the CSI-D cognitive section (defined as a score of < 25.5 out of 30) or a poor performance on the 5-Word Test. Use of this adjusted instrument revealed a prevalence of cognitive impairment with no dementia (CIND) of 10.4%.26 Botswana Researchers screened 372 participants aged ≥ 60 years for several chronic diseases. Cognitive impairment was assessed using an adapted but non- validated version of the Mini–Mental State Examination (MMSE), which omitted sections that required writing or reading and adapted other sections to the local context. A 9% prevalence of cognitive impairment was reported without measures of uncertainty, with 777Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422 Systematic reviews Dementia and cognitive impairment in sub-Saharan AfricaAngelique Mavrodaris et al. (c on tin ue s. . . ) Ta bl e 2. Sc re en in g to ol s a nd d ia gn os tic cr ite ria u se d in st ud ie s o bt ai ne d fr om a sy st em at ic re vi ew o f t he li te ra tu re o n th e pr ev al en ce s o f d em en tia a nd co gn iti ve im pa irm en t i n su b- Sa ha ra n Af ric a Co un tr y, re fe re nc e Sc re en in g to ol s Di ag no st ic cr ite ria fo r d em en tia Di ag no st ic cr ite ria fo r c og ni tiv e im pa irm en t Be ni n Gu er ch et e t a l.2 6 CS I-D , S CE B, Cl in ic al a ss t In di vi du al s w ith p oo r p er fo rm an ce s o n th e CS I-D o r 5 -W or d Te st u nd er w en t a st ru ct ur ed in te rv ie w b y a se ni or n eu ro lo gi st w ith a F on tr an sla to r. T he in te rv ie w in cl ud ed a d es cr ip tio n an d as se ss m en t o f c og ni tiv e sy m pt om s, ac tiv iti es o f d ai ly li vi ng , a nd so ci al h ab its ; a m ed ic al hi st or y; a nd a c lin ic al e xa m in at io n. A dd iti on al c og ni tiv e te st s i nc lu de d th e or al F re e an d Cu ed Se le ct iv e Re m in di ng Te st , Z az zo ’s Ca nc el la tio n Ta sk a nd Is aa c’s S et Te st o f V er ba l F lu en cy . T he di ag no sis o f d em en tia w as m ad e ac co rd in g to D SM -IV c rit er ia a nd c lin ic al c rit er ia p ro po se d by th e N IN CD S- AD RD A II fo r A lz he im er d ise as e. O th er ty pe s o f d em en tia th at w er e di ag no se d w er e ba se d on a h ist or y of st ro ke a nd o th er c lin ic al fe at ur es . Th e CS I-D w as u se d be ca us e of th e lo w li te ra cy le ve l a nd th re e te st s f ro m th e SC EB w er e us ed : t he te m po ra l o rie nt at io n te st , 5 -W or d Te st a nd th e se m an tic v er ba l fl ue nc y ta sk (t he c lo ck -d ra w in g te st w as n ot in cl ud ed ). A qu es tio nn ai re w as u se d to o bt ai n m ed ic al h ist or y an d sc re en in g to ol s w er e ad m in ist er ed to p eo pl e > 6 5 ye ar s. Be ca us e of th e hi gh il lit er ac y ra te , 3 0 w as th e hi gh es t s co re fo r t he C SI -D (t he te st a ss es sin g pr ax ia s w as u se d; c ur re nt ye ar a nd in fo rm an t s ec tio ns w er e ex cl ud ed ). Co gn iti ve im pa irm en t w as de fin ed a s e ith er p oo r p er fo rm an ce o n th e CS I-D (< 2 5. 5 co rre ct it em s o f 3 0 te st ed ) o r t he 5 -W or d Te st (< 1 0 of 1 0) . Bo ts w an a Cl au se n et a l.2 7 M M SE N ot a pp lic ab le Fa ce -t o- fa ce in te rv ie w s w ith q ue st io nn ai re s a nd a st an da rd ize d cl in ic al ex am in at io n w er e us ed . A c ul tu ra lly a da pt ed v er sio n of th e M M SE (n ot va lid at ed ) w as u se d to a cc ou nt fo r e du ca tio n le ve l. I te m s r eq ui rin g w rit in g an d re ad in g sk ill s a nd g eo m et ric fi gu re s w er e om itt ed . S om e ite m s w er e sli gh tly a lte re d to a da pt to lo ca l c on te xt s. Co gn iti ve im pa irm en t w as d efi ne d as a sc or e of < 1 6 co rre ct it em s o f 2 6 te st ed . Ce nt ra l A fr ic an Re pu bl ic a nd th e Co ng o Gu er ch et e t a l.2 4 CS I-D , 5 -W or d Te st , D SM -IV , N IN CD S- AD RD A II Su bj ec ts w ith su sp ec te d de m en tia u nd er w en t a n eu ro lo gi ca l e xa m in at io n an d ps yc ho m et ric al te st s, in cl ud in g th e Fr ee a nd C ue d Se le ct iv e Re m in di ng Te st , Z az zo ’s Ca nc el la tio n Ta sk a nd Isa ac ’s Se t T es t o f V er ba l F lu en cy . T he d ia gn os is of d em en tia w as m ad e ac co rd in g to D SM -IV cr ite ria a nd c lin ic al c rit er ia p ro po se d by th e N IN CD S- AD RD A II fo r A lz he im er d ise as e. V as cu la r de m en tia w as d ia gn os ed o n th e ba sis o f t he H ac hi ns ki sc al e. Su bj ec ts a ge d > 6 5 ye ar s w er e in te rv ie w ed b y tra in ed fi el d in ve st ig at or s a nd in st ru m en ts a nd sc al es (t he C SI -D a nd 5 -W or d Te st ) w er e pr es en te d in lo ca l la ng ua ge s. Su bj ec ts w ith a p oo r p er fo rm an ce o n th e CS I-D (< 2 5. 5 co rre ct ite m s o f 3 0 te st ed ) o r t he 5 -W or d Te st (< 1 0 of 1 0) w er e cl as sifi ed a s h av in g co gn iti ve im pa irm en t o r s us pe ct ed d em en tia a nd in vi te d to u nd er go c lin ic al as se ss m en t b y a ne ur ol og ist . N ig er ia Yu su f e t a l.2 8 CS I-D , C ER AD , BD S, C lin ic al a ss t Sc re en in g in st ru m en ts w er e tra ns la te d in to H au sa a nd a ll re se ar ch er s w er e tra in ed in th e us e of in st ru m en ts . T he B os to n N am in g Te st a nd th e Co ns tru ct io na l P ra xi s T es t f ro m th e CE RA D w er e om itt ed a nd re pl ac ed b y th e st ic k de sig n te st . A p ilo t s tu dy w as c on du ct ed . A ll su bj ec ts w er e in te rv ie w ed in H au sa a nd u nd er w en t p hy sic al e xa m in at io n. T he d ia gn os is of d em en tia w as b as ed o n di ag no st ic c rit er ia in b ot h th e IC D -1 0 (v as cu la r d em en tia ) a nd th e D SM -IV (A lz he im er d ise as e) a nd w as c on fir m ed b y co ns en su s ( tw o ph ys ic ia ns ). N ot a pp lic ab le U w ak w e et a l.2 9 CS I-D , 1 0- W D RT N ot a pp lic ab le Th e fu ll 10 /6 6 D em en tia R es ea rc h Gr ou ps su rv ey p ro to co l, i nc lu di ng as ce rt ai nm en t o f c og ni tiv e im pa irm en t, w as a dm in ist er ed . I nt er vi ew s co m pr ise d co gn iti ve te st in g, a c lin ic al in te rv ie w , c ol le ct io n of d at a on he al th b eh av io ur a nd se rv ic e us e an d an in fo rm an t i nt er vi ew . C og ni tio n w as a ss es se d by C SI -D –a ss oc ia te d m em or y ite m s a nd b y a 10 -W or d Li st to de te rm in e th e le ve l o f i m m ed ia te a nd d el ay ed re ca ll, fo r w hi ch a n im pa ire d sc or e w as d efi ne d as 1 .5 st an da rd d ev ia tio ns b el ow th e ag e- a nd e du ca tio n- sp ec ifi c no rm . Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422778 Systematic reviews Dementia and cognitive impairment in sub-Saharan Africa Angelique Mavrodaris et al. (. . . co nt in ue d) Co un tr y, re fe re nc e Sc re en in g to ol s Di ag no st ic cr ite ria fo r d em en tia Di ag no st ic cr ite ria fo r c og ni tiv e im pa irm en t Gu re je e t a l.3 0 10 -W D RT Tr ai ne d re se ar ch in te rv ie w er s c on du ct ed fa ce -t o- fa ce in te rv ie w s w ith se le ct ed p eo pl e flu en t i n Yo ru ba . Q ua lit y co nt ro l m ea su re s w er e us ed . C og ni tio n w as a ss es se d us in g an a da pt ed v er sio n of th e 10 -W D RT . T hi s t oo l w as u se d to d ia gn os e pr ob ab le d em en tia (a te st -re te st st ud y of a sm al le r s am pl e w as c on du ct ed a nd sh ow ed g oo d re lia bi lit y) . N ot a pp lic ab le O ch ay i e t a l.3 1 CS I-D , D SM -IV In di vi du al s w er e in te rv ie w ed b y st ud y in ve st ig at or s, us in g th e CS I-D . W he n ne ce ss ar y, a fa m ily m em be r p ro vi de d su pp le m en ta ry in fo rm at io n. D em en tia w as d efi ne d as a C SI -D sc or e < 2 8. 5 (a s i n th e Ib ad an st ud y an d it w as c ro ss -c ul tu ra lly v al id at ed ). N ot a pp lic ab le Ba iy ew u et a l.3 2 CS I-D , C lin ic al as st , C ER AD N ot a pp lic ab le Re sid en ts w er e sc re en ed w ith th e CS I-D . C ut -o ff sc or es w er e us ed to c la ss ify su bj ec ts a s h av in g a lo w , m ed iu m o r h ig h pr ob ab ili ty o f d em en tia a nd to in fo rm fu rt he r c lin ic al sc re en in g. A ll su bj ec ts w ith a h ig h pr ob ab ili ty o f de m en tia (t ho se w ith a lo w C SI -D sc or e) , 5 0% w ith a m ed iu m p ro ba bi lit y of d em en tia (t ho se w ith a b or de rli ne C SI -D sc or e) a nd 5 % w ith a lo w pr ob ab ili ty o f d em en tia (t ho se w ith a h ig h CS I-D sc or e) w er e se le ct ed fo r t he cl in ic al a ss es sm en t p ha se (i .e . p hy sic ia n ex am in at io n, in fo rm an t i nt er vi ew , co gn iti ve a ss es sm en t a nd la bo ra to ry a nd im ag in g st ud ie s) . P ar tic ip an ts w er e as se ss ed w ith th e CE RA D n eu ro ps yc ho lo gi ca l b at te ry , w hi ch in cl ud es th e M M SE , W or d Li st L ea rn in g, th e An im al F lu en cy Te st , t he B os to n N am in g Te st a nd C on st ru ct io na l P ra xi s. A co ns en su s d ia gn os tic c on fe re nc e in vo lv in g ex pe rie nc ed c lin ic ia ns c on fir m ed e ac h di ag no sis . T he c rit er ia fo r C IN D w er e as fo llo w s: th e in fo rm an t r ep or te d a de cl in e in th e su bj ec t’s c og ni tio n le ve l, a ph ys ic ia n de te ct ed im pa irm en t i n th e su bj ec t’s c og ni tio n le ve l a nd /o r th e su bj ec t’s c og ni tiv e te st sc or e( s) w er e be lo w a pp ro xi m at el y th e se ve nt h pe rc en til e; a nd th e su bj ec t h ad n o im pa irm en t i n da ily li vi ng ta sk s. Su bt yp es of C IN D w er e as sig ne d on th e ba sis o f p re su m ed e tio lo gy . T he c rit er ia fo r CI N D w er e co m pa ra bl e w ith th os e de fin ed b y th e W or ld H ea lth O rg an iz at io n. U w ak w e3 3 SR Q -2 4, G M S Pa rt ic ip an ts a ge d > 6 0 ye ar s w er e in te rv ie w ed w ith th e SR Q -2 4 an d GM S. A c ut -o ff sc or e of 5 w as u se d fo r t he S RQ -2 4 (v al id at ed a nd u se d in p re vi ou s N ig er ia n st ud ie s) . V al id at io n of th e GM S oc cu rre d on ly b y m ea ns o f p ilo t t es tin g, a fte r w hi ch 8 q ue st io ns w er e re w or de d or m od ifi ed . A n op en h ea lth in te rv ie w in g bo ok le t w as u se d du rin g th e GM S in te rv ie w . C lin ic al de ta ils w er e as se ss ed b y tw o se ni or p sy ch ia tri st s a nd re -e va lu at ed b y a pr of es so r o f p sy ch ia tr y. IC D -1 0 cr ite ria w er e us ed to d ia gn os e de m en tia . N ot a pp lic ab le O gu nn iy i et a l. a nd ot he rs 12 ,1 5, 16 ,1 8– 23 CS I-D , C lin ic al as st , C ER AD Tr ai ne d in te rv ie w er s a dm in ist er ed th e CS I-D (p ilo t t es te d an d va lid at ed ). A di sc rim in an t fu nc tio n sc or e w as d er iv ed (p er fe ct sc or e, 3 3) . S ub je ct s w er e di vi de d in to th re e pe rfo rm an ce gr ou ps (g oo d, in te rm ed ia te a nd p oo r) on th e ba sis o f t he ir di sc rim in an t f un ct io n sc or e, a fte r w hi ch 5 % o f g oo d pe rfo rm er s, 50 % o f i nt er m ed ia te p er fo rm er s a nd a ll po or p er fo rm er s w er e se le ct ed fo r c lin ic al a ss es sm en t ( a st ru ct ur ed in te rv ie w w ith a n in fo rm an t o f t he su bj ec t, fo cu sin g on c og ni tiv e fu nc tio ns , a ct iv iti es o f d ai ly li vi ng , s oc ia l h ab its a nd p as t a nd c ur re nt m ed ic al h ist or y) . E ac h su bj ec t u nd er w en t d et ai le d ne ur op sy ch ol og ic al te st in g, fo llo w ed b y cl in ic al e xa m in at io n an d re le va nt la bo ra to ry te st s, in cl ud in g co m pu te d to m og ra ph y of th e br ai n. A c on se ns us d ia gn os is w as m ad e fir st o n sit e an d la te r b lin dl y, fro m o th er si te s. Th e di ag no sis o f d em en tia su bt yp es w as b as ed o n cl in ic al fi nd in gs a nd a cc or de d w ith IC D -1 0 an d N IN CD S- AD RD A II cr ite ria . N ot a pp lic ab le BD S, B le ss ed D em en tia R at in g Sc al e; C ER AD , C on so rti um to E st ab lis h a Re gi st ry fo r A lzh ei m er D ise as e; C IN D, c og ni tiv e im pa irm en t, no d em en tia ; C lin ic al a ss t, Cl in ic al A ss es sm en t; CS I-D , C om m un ity S cr ee ni ng In te rv ie w fo r D em en tia ; D SM -IV , D ia gn os tic a nd St at ist ica l M an ua l o f M en ta l D iso rd er s, Fo ur th R ev isi on ; G M S, G er ia tri c M en ta l S ta te S ch ed ul e; IC D -1 0, In te rn at io na l C la ss ifi ca tio n of In fe ct io us D ise as es , T en th R ev isi on ; M M SE , M in i-M en ta l S ta te E xa m in at io n; N IN CD S- AD RD A II, N at io na l In st itu te o f N eu ro lo gi ca l a nd C om m un ic at iv e D iso rd er a nd S tro ke a nd th e Al zh ei m er D ise as e an d Re la te d D iso rd er s A ss oc ia tio n II; SC EB , S ho rt Co gn iti ve E va lu at io n Ba tte ry ; S RQ -2 4, S el f-R ep or tin g Q ue st io nn ai re ; 1 0- W D RT , 1 0- W or d D el ay R ec al l T es t. 779Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422 Systematic reviews Dementia and cognitive impairment in sub-Saharan AfricaAngelique Mavrodaris et al. no distinction made between cognitive impairment with or without dementia.27 Central African Republic and Congo Studies conducted in Bangui and Braz- zaville reported CIND prevalences of 25% and 18.8%, respectively.24 Nigeria A study from Dunukofia screened 914 participants with three memory tests (CSI-D and 10-word immediate and delayed recall). A total of 11.8% of par- ticipants had just one memory test in- dicating cognitive impairment, whereas cognitive impairment was detected in 9.9% by two or more memory tests.29 A study from Uwan, described above, used the SRQ-24 and the GMS to screen 164 participants older than 60 years and 34 (20.7%) reported forgetful- ness, which may have been indicative of cognitive impairment.33 The Ibadan study group also studied cognitive impairment in 2000 in both rural and urban regions. They found a CIND prevalence of 6.3% among 2487 participants who were screened us- ing the CSI-D tool and were assessed clinically. The sample used for this study included some of the participants in the 1995 study of dementia described above, as well as additional participants. The study also followed up 87 of the 152 patients with CIND and found that after 2 years 16.1% had developed dementia, 58.6% still had a diagnosis of CIND and 25.3% had normal cognitive function.32 Discussion To our knowledge, this is the first systematic review of the prevalence of dementia and cognitive impairment in older populations in sub-Saharan Africa. Eleven studies were identified and all had a cross-sectional design. Prevalences varied widely between countries and by publication date. The predominant factors associated with a higher prevalence of dementia were older age and female sex. Older age was strongly associated with dementia and cognitive impairment in all studies and similar associations have been reported globally.34 Female sex was a risk factor for both outcomes in five studies12,24,30,31 and has been confirmed in many in- ternational studies.34 The majority of studies were from Nigeria and western and central Africa, with only one from southern Africa and none from eastern Ta bl e 3. M et ho do lo gi ca l q ua lit y o f a nd va lid ity sc or es fo r s tu di es o bt ai ne d fr om a sy st em at ic re vi ew o f t he li te ra tu re o n th e pr ev al en ce s o f d em en tia a nd co gn iti ve im pa irm en t i n su b- Sa ha ra n Af ric a Co un tr y, re fe re nc e Va lid ity sc or in g cr ite rio n Va lid ity sc or e, ou t o f 7 Ta rg et p op ul at io n w el l d efi ne d Pr ob ab ili ty sa m pl in g us ed Sa m pl e m at ch ed ta rg et po pu la tio n Da ta co lle ct io n m et ho d st an da rd ize d To ol va lid To ol re lia bl e An al ys is in clu de d 95 % CI Be ni n Gu er ch et e t a l. 2 00 92 6 Ye s Ye s Ye s Ye s Ye s N K Ye s 6 Bo ts w an a Cl au se n et a l. 2 00 52 7 Ye s Ye s Ye s Ye s N o N K N o 4 Ce nt ra l A fr ic an R ep ub lic Gu er ch et e t a l. 2 01 02 4 Ye s Ye s Ye s Ye s Ye s N K Ye s 6 Co ng o Gu er ch et e t a l. 2 01 02 4 Ye s Ye s Ye s Ye s Ye s N K Ye s 6 N ig er ia Yu su f e t a l. 2 01 12 8 Ye s Ye s Ye s Ye s Ye s N K Ye s 6 U w ak w e et a l. 2 00 92 9 Ye s N K Ye s Ye s Ye s N K N o 4 Gu re je e t a l. 2 00 63 0 Ye s Ye s Ye s Ye s Ye s Ye s Ye s 7 O ch ay i e t a l. 2 00 63 1 Ye s Ye s Ye s Ye s Ye s N K Ye s 6 Ba iy ew u at a l 2 00 23 2 Ye s Ye s Ye s Ye s Ye s Ye s N o 7 U w ak w e 20 00 33 Ye s Ye s Ye s Ye s Ye s N K N o 5 O gu nn iy i e t a l. a nd ot he rs 12 ,1 5, 16 ,1 8– 23 Ye s Ye s Ye s Ye s Ye s Ye s Ye s 7 CI , c on fid en ce in te rv al ; N K, n ot k no w n. Systematic reviews 780 Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422 Africa. We are aware of another study currently being conducted in a rural community of 2000 households in Bloemfontein, South Africa, but to date only a pilot study has been completed, with prevalence of 6.4% for dementia diagnosed by DSM-IV criteria.35 These studies have several limita- tions. Dementia involves a change in function and cognition but in a cross- sectional study such change is difficult to determine and assessment is reliant on the reports of individuals close to the individual. Survivor bias may have influenced prevalence data for both de- mentia and cognitive impairment, since individuals who are more vulnerable to cognitive impairment and poor health would be less likely to survive into old age in sub-Saharan Africa. The generalizability of these studies is also limited. The more recent esti- mates of dementia prevalence remain lower than those reported in Europe (6.2%; 4% for Alzheimer disease) and the United States of America (8%; 6% for Alzheimer disease),11,13–16 but this comparison is flawed because the age structure of the population older than 65 years in sub-Saharan Africa and Europe will differ. In sub-Saharan Africa, there is a higher proportion of individuals aged 66–80 years and a smaller propor- tion aged 81 years and older, leading to a lower overall prevalence of dementia, which is predominantly a disease of older people. Cognitive impairment prevalences of 3% to 19% among people older than 65 years in other parts of the world (range: 3–19%) are comparable with those reported by studies in our review.36 Studies of migrant African origin populations now living in Europe or North America have reported higher prevalences of cognitive impairment (range: 8–34%) but the majority of these studies included African-Carib- bean participants or did not clearly distinguish the ethnic origins of study subjects. 37,38 Further research of first- generation sub-Saharan Africa migrant populations may provide more accurate data and insight into environmental fac- tors associated with dementia. There are challenges to assessing cognitive change and mental health in sub-Saharan Africa. Social impairment is not as highly associated with cognitive impairment in African communities, compared with communities in devel- oped countries. The social functions and participation of elderly individuals in African culture differ from those found in Western cultures and factors associated with normal functioning in old people also differ.32 This may be because the DSM-IV and ICD-10 screening instruments require certain levels of social impairment to confirm clinical dementia and thus may lead to under-diagnosis in sub-Saharan Africa. The move from participant-based to informant-based cognitive tests has the potential to diminish the effects of edu- cation level and cultural biases because the informant reports direct changes in cognition on the basis of their knowl- edge of the subject’s prior cognitive and functional status. The CSI-D combines both approaches and incorporates a direct cognitive assessment and it has been accepted as a culturally adaptable screening tool in some African coun- tries. Further development and refine- ment of the CSI-D is needed and future studies of prevalence should use this or some other validated screening tool. The 10/66 Dementia Research Group has developed evidence-based diagnostic tools that would facilitate inter-cultural research.39 Large cross-sectional surveys in both rural and urban populations from more countries in sub-Saharan Africa would aid health-care planning. Lon- gitudinal studies examining incidence and predictors and factors modifying the rate and severity of cognitive decline specific to populations in this region are also needed. Qualitative analyses investi- gating cultural perceptions of dementia from the perspectives of the community, caregivers and individuals with demen- tia would offer insight into access issues and improvements in health care. While still experiencing high mortal- ity and fertility rates and heavily burdened by infectious disease, the population of sub-Saharan Africa is ageing and a rise in noncommunicable chronic diseases is inevitable. With no known cure or preventative intervention, dementia and cognitive impairment are set to be one of the biggest public health challenges in sub-Saharan Africa in the 21st century. ■ Acknowledgements We thank Karen Rees for her assistance with statistical methods. Margaret Tho- rogood is also affiliated with Warwick Medical School, University of Warwick. Funding: AM held an Academic Clinical Fellowship post which was funded by the United Kingdom of Great Britain and Northern Ireland National Institute for Health Research (NIHR). The views expressed are those of the authors and not necessarily those of the United Kingdom National Health Service, the NIHR or the United Kingdom Department of Health. The sponsor had no role in study design, data collection, data analysis, data inter- pretation or writing of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication. Competing interests: None declared. صخلم يجهنم ضارعتسا :ىبركلا ءارحصلا بونج ايقيرفأ في يننسلما صاخشلأا ينب يكاردلإا لللخاو فرلخا راشتنا تلادعم لللخا راشتنا لوح تافلؤملل يجهنم ضارعتسا ءارجإ ضرغلا .ىبركلا ءارحصلا بونج ايقيرفأ في فرلخاو يكاردلإا تاصخللما نع ةينوتركلإ تانايب دعاوق سخم في ثحبلا مت ةقيرطلا ضارعتسلا حلصت يتلا ةيثحبلا قارولأا لىع فرعتللو ةلصلا تاذ نانثا قفتا اذإ ينمضتلل ةلحاص ةساردلا تناكو .ةلماكلا اهصوصن ةطبترم تلاالح وأ ،قسانتم ميمصت تاذ انهأ لىع ينفلؤلما نم ىوتسم لىع تانايب نع تغلبأو ،يعطقم ميمصت تاذ وأ طباوضب بركلأا دوسلا ةقرافلأا ينغلابلا صاخشلأا لىع تصرتقاو ؛ناكسلا ؛“نسلا رابك” وأ “يننسم” منهأب نوفصوي نيذلا وأ ًاماع 50 نم ءارحصلا بونج ايقيرفأ في ينميقلما دارفلأل تانايب نع تغلبأو وأ يكاردلإا للخلل لقلأا لىع دحاو سايقم نع تغلبأو ؛ىبركلا عجارم في ثحبلا متو .يكاردلإا روهدتلاب ةلصتلما ةيريسرلا جئاتنلا ةيفاضلإا تاروشنلما ديدحتل انتسارد في ةنمضتلما ةيثحبلا قارولأا للاخ نم متي ينمضتلا نأشب تافلالخا في لصفلا ناكو .ةحترقلما لكشب تانايبلا صلاختسا متو .ينفلؤلما لك اهيف كترشي تاشقانم اهعضو ةرماتسا مادختساب ،ينفلؤلما نم يننثا ةطساوب لقتسم Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422 781 Systematic reviews Dementia and cognitive impairment in sub-Saharan AfricaAngelique Mavrodaris et al. .ةيثحبلا قارولأا نم ةنيع لىع اهرابتخا متو نوفلؤلما متو ؛ةديرف ةيثحب ةقرو 2320 لياجمإ لىع روثعلا مت جئاتنلا ينمضت متو .اهنم ةسارد يننماثو عبسل لماكلا صنلا ضارعتسا اهلك تشرن دقو ؛ةيعطقم ةسارد 11 مضت ةيثحب ةقرو ةشرع عست يننب في تاساردلا تيرجأو .2011 لىإ 1995 نم ةترفلا للاخ تجردأو ،اييرجينو وغنوكلاو ىطسولا ايقيرفأ ةيروهجمو اناوستبو ،اييرجين في % 0 نم فرلخا راشتنا حوارتو .كراشم 10500 لياوح ًاضيأ ،)11.8–8.6 :ةقثلا لصاف ،% 95 ةقثلا لصاف( % 10.1 لىإ ،اييرجين في ،% 6.3 نم يكاردلإا لللخا راشتنا حوارتو .اييرجين في في )29.0–21.2 :ةقثلا لصاف ،% 95 ةقثلا لصاف( % 25 لىإ .ىطسولا ايقيرفأ ةيروهجم في يكاردلإا لللخاو فرلخا راشتنا تلادعم تنيابت جاتنتسلاا نم ليلقلا دوجو عم ،عساو ردقب ىبركلا ءارحصلا بونج ايقيرفأ .تافلؤلما في ثحبلا اهنع فشك يتلا ةروشنلما تاساردلا 摘要 撒哈拉以南非洲老年人痴呆和认知障碍发病率：系统评价 目的 进行撒哈拉以南非洲认知障碍和痴呆发病率相关 文献的系统评价。 方法 检索五个电子数据库的相关摘要，并确定出符合 全文评价条件的文章。将研究纳入的条件是 ：有两位 作者同意某研究具有队列、病例对照或横断面设计并 且报告了群体水平的数据 ；研究限于年龄在 50 岁以 上或被描述为“上年纪”或“年老”的非洲成年黑人； 报告居住在撒哈拉以南非洲个体的数据 ；报告至少一 种认知障碍或认知衰退相关临床结果的量度。对于我 们研究中所纳入的文章，也对其参考文献进行检索， 以确定更多的其他候选发表文章。在涉及所有作者的 讨论中对有关是否纳入的分歧进行评判。数据由两位 作者独立提取，提取时使用了作者编制并在论文样本 上进行过检测的表格。 结果 总计找到 2320 篇单独的文章 ；对 87 篇全文进行 评价。纳入了 11 项横断面研究的 19 篇文章 ；所有文 章都发表于 1995–2011 年间。这些研究在贝宁、博茨 瓦纳、中非共和国、刚果和尼日利亚开展，招募了约 1.05 万名患者。痴呆的发病率范围在尼日利亚的 0% 到同 样是尼日利亚的 10.1%（95% 置信区间，CI：8.6–11.8） 之间。认知障碍的发病率范围在尼日利亚的 6.3% 到中 非共和国的 25% 之间（95% CI ：21.2–29.0）。 结论 痴呆和认知障碍的发病率在撒哈拉沙漠以南非洲 差异巨大，通过文献检索发现的已发表研究很少。 Résumé Prévalence de la démence et des troubles cognitifs chez les personnes âgées en Afrique sub-saharienne : une étude systématique Objectif Réaliser une étude systématique de la littérature consacrée à la prévalence de la déficience cognitive et de la folie en Afrique subsaharienne. Méthodes Cinq bases de données ont été fouillées afin de trouver des résumés pertinents et d’identifier les journaux éligibles pour une étude en texte intégral. Une étude était inclue si deux auteurs reconnaissaient qu’elle était de type cohorte, cas-témoins ou transversale et relevait des données de l’l’échelle de la population; qu’elle était limitée aux adultes africains noirs âgés de plus de 50 ans ou décrits comme «âgés» ou «vieux»; qu’elle relevait des données concernant des individus résidant en Afrique subsaharienne; et qu’elle relevait au moins une mesure de déficience cognitive ou de résultats cliniques liés au déclin cognitif. Les références de journaux inclus dans notre étude ont été fouillées pour identifier des publications supplémentaires potentielles. Les désaccords quant à une inclusion étaient réglés au cours de discussions impliquant tous les auteurs. Des données étaient extraites indépendamment par deux auteurs, au moyen d’un formulaire développé par les auteurs et testées sur un échantillon de journaux. Résultats Au total, 2320 journaux uniques ont été trouvés; le texte intégral de 87 d’entre eux a été analysé. Dix-neuf journaux présentant 11 études transversales ont été inclus; tous avaient été publiés entre 1995 et 2011. Les études avaient eu lieu au Bénin, au Botswana, en République centrafricaine, au Congo et au Nigéria et impliquaient environ 10 500 participants. La prévalence de la démence allait de 0% au Nigéria à 10,1% (intervalle de confiance 95%, IC: 8,6-11,8) également au Nigéria. La prévalence de la déficience cognitive allait de 6,3% au Nigéria à 25% (IC 95%: 21,2-29,0) en République centrafricaine. Conclusion Les prévalences de démence et de déficience cognitive en Afrique subsaharienne variaient sensiblement et peu d’études publiées ont été révélées par la recherche de littérature. Резюме Распространенность деменции и когнитивных нарушений среди пожилого населения стран Африки к югу от Сахары: систематический обзор Цель Выполнить систематический обзор публикаций, посвященных распространенности когнитивных нарушений и деменции в странах Африки к югу от Сахары. Методы Поиск выдержек подходящей тематики и публикаций для полнотекстового обзора был выполнен в пяти базах данных. Исследование включалось в обзор в том случае, если, по мнению двух авторов, оно проводилось либо по когортной схеме, либо по перекрестной схеме, либо по схеме «случай–контроль», а его результатами были данные на уровне популяции;касалось исключительно чернокожих африканцев в возрасте старше 50 лет или описывавшихся как «пожилые» или «старые»; содержало сведения о жителях стран Африки к югу от Сахары; в нем упоминалось как минимум об одном параметре когнитивных нарушений или клинических исходах, связанных с ухудшением когнитивной функции. Дополнительный поиск публикаций- кандидатов, заслуживавших включения в обзор, проводился по ссылкам из работ, охваченных нашим исследованием. Урегулирование разногласий относительно возможности Bull World Health Organ 2013;91:773–783 | doi: http://dx.doi.org/10.2471/BLT.13.118422782 Systematic reviews Dementia and cognitive impairment in sub-Saharan Africa Angelique Mavrodaris et al. включения публикации в обзор осуществлялось посредством обсуждения с привлечением всего авторского коллектива. Извлечение данных осуществлялось двумя авторами независимо друг от друга при помощи авторской формы, апробированной на ряде тестовых публикаций. Результаты Всего было обнаружено 2 320 отдельных публикаций; 87 из них были подвергнуты полнотекстовому анализу. В обзор вошли девятнадцать публикаций, вышедших в 1995–2011 гг.; в одиннадцати из них были представлены материалы перекрестных исследований. Исследования проводились в Бенине, Ботсване, Конго, Нигерии и Центральноафриканской Республике и охватили около 10 500 человек. Распространенность деменции варьировалась от 0% в Нигерии до 10,1% (доверительный интервал (ДИ) 95%: от 8,6 до 11,8) также в Нигерии. Распространенность когнитивных нарушений варьировалась от 6,3% в Нигерии до 25% (ДИ 95%: от 21,2 до 29,0) в Центральноафриканской Республике. Вывод По данным нескольких опубликованных исследований, о б н а р у ж е н н ы х в р е зу л ьта те п о и с к а л и те р а т у р ы , распространенность деменции и когнитивных нарушений в странах Африки к югу от Сахары существенно разнится. Resumen La prevalencia de la demencia y el deterioro cognitivo en las personas mayores en el África subsahariana: una revisión sistemática Objetivo Realizar una revisión sistemática de la literatura sobre la prevalencia del deterioro cognitivo y la demencia en el África subsahariana. Métodos Se hicieron búsquedas en cinco bases de datos electrónicas a fin de hallar resúmenes pertinentes e identificar los documentos que cumplieran con los requisitos para una revisión del texto completo. Los estudios se incluyeron cuando dos autores coincidían en que el diseño era de cohorte, de casos y controles o transversal y si presentaban los datos a nivel de población, si se limitaban a los adultos africanos negros mayores de 50 años o descritos como “personas mayores” o “ancianas”, si incluían datos correspondientes a las personas que residen en el África subsahariana y si presentaban, al menos, un grado de deterioro cognitivo o resultados clínicos relevantes sobre el deterioro cognitivo. Se realizaron búsquedas de las referencias de los artículos incluidos en nuestro estudio a fin de identificar más publicaciones que cumplieran los requisitos, se arbitraron los desacuerdos sobre la inclusión en las discusiones que involucraban a todos los autores y se recogieron los datos de forma independiente por dos autores mediante un formulario desarrollado por los autores y probado en una muestra de trabajos. Resultados Se halló un total de 2320 documentos únicos y se revisó el texto completo de 87 de ellos. Se seleccionaron diecinueve documentos que incluían 11 estudios transversales, todos ellos publicados entre 1995 y 2011. Los estudios tuvieron lugar en Benin, Botswana, la República Centroafricana, el Congo y Nigeria, en los que se registraron aproximadamente 10 500 participantes. La prevalencia de la demencia varió del 0 % en Nigeria, al 10,1 % (intervalo de confianza del 95 %, IC: 8,06-11,08), también en Nigeria. 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