Prevalence rates of impaired glucose tolerance and diabetes mellitus in various Pacific populations according to the new WHO criteria*

Bulletin of the World Health Organization, 60 (2): 279- 282 (1982) Prevalence rates of impaired glucose tolerance and diabetes mellitus in various Pacific populations according to the new WHO criteria* PAUL ZIMMET,' RICHARD TAYLOR, & SUNNY WHITEHOUSE3 This report gives the prevalence rates ofimpaired glucose tolerance (IG T) and diabetes mellitus (DM) for several Micronesian, Polynesian, and Melanesian populations in the Pacific region according to the new WHO criteria. The Micronesian population ofNauru show the highest prevalence rates of both IGT (22.7%) and DM (30.3 %) -53% of the adult population thus demonstrating abnormal glucose tolerance. The lowest prevalence rates of both IGT (4.5%) and DM (1.5%) were seen in the rural Melanesian population of the main island ofNew Caledonia. Because of the different methods, age-stratifi- cation of samples, and diagnostic criteria used in the various studies, comparison of diabetes prevalence rates in different countries (and even populations within the same country) has been almost impossible (I -3). In response to a number of requests for standardiz- ation of the methods used for the oral glucose tolerance test (OGTT) and for standard definitions of diabetes mellitus and other abnormalities of glucose tolerance (3-5), the WHO Expert Committee on Diabetes Mellitus has recently recommended diag- nostic procedures and criteria for worldwide use (6). For the purposes of our epidemiological studies, the criteria for impaired glucose tolerance (IGT) and diabetes mellitus (DM) were as follows: IGT: 2-hour plasma glucose a > 8 and < I I mmol/litre (1.4 - 2.0 g/litre) DM: 2-hour plasma glucose 11 mmol/litre ()> 2.0 g/litre) (fasting plasma glucose ) 8 mmol/litre ( > 1.4 g/litre) was used if the 2-hour value was unavailable). * From the WHO Collaborating Centre for Epidemiology of Diabetes, Royal Southern Memorial Hospital, Caulfield, 3162, Australia. This work was supported by the National Health and Medical Research Council of Australia, the World Health Organization, the South Pacific Commission, and the National Institutes of Health, USA (Grant RO 1 AM 2544601). Head, WHO Collaborating Centre for Epidemiology of Diabetes. 2 Epidemiologist. 3 Computer Fellow. " After a 75-g oral glucose load. A 2-hour plasma glucose of 11 mmol/litre was chosen as the cut-off point for DM because of evi- dence from prospective studies on the development of frank diabetes or diabetic complications (both macro- and microvascular) in groups of people with various degrees of glucose intolerance (7, 8). Furthermore, the recognition of bimodality in the frequency distribution of 2-hour post-load glucose levels in some populations with a high prevalence of diabetes (9- 11) supports a value of 11 mmol/litre for the definition of DM since the anti-modal point is around this level. We have reported previously on studies of diabetes prevalence in Nauru (12, 13), Tuvalu (14), Western Samoa (15), and New Caledonia (16). The criterion used for the definition of diabetes in all but the New Caledonia study was a 2-hour plasma glucose level of > 1.6 g/litre in order to be able to compare the results with those of other international studies (17). Now we report our prevalence data using the new cri- teria adopted by the WHO Expert Committee. The rates reported here are directly comparable, since all the populations have been age-standardized against the 1976 Western Samoa census (18) -a reference we intend to use for future Pacific studies. MATERIALS AND METHODS The studies were performed between 1975 and 1979 and the methods used were identical for each. Full details of these studies have been published elsewhere (12- 16). The subjects were not prepared for the test 4174 -279- P. ZIMMET ET AL. with a formal high carbohydrate diet, and all had been on an unrestricted diet. The average Pacific island daily diet contains over 150 g of carbo- hydrate. All subjects were asked to fast and to present them- selves at the survey centre between 08 h 00 and 10 h 00. Two hours after the glucose load, a further blood sample was taken. All blood samples were centrifuged, separated, frozen, and stored. They were sent to Melbourne, Australia, in one batch, packed in dry ice, at the con- clusion of each survey. As a precaution against loss, the 2-hour plasma glucose values were also measured on site with the Yellow Springs Instrument Glucose Analyser (model 23AM), which uses a glucose oxidase method. Age standardization was undertaken in order that the prevalence in the different population groups can be directly compared. The direct method was used and a standard error was calculated according to the method described by Armitage (19). For standardization calculations, the populations were broken down into six age groups (20 - 25, 25 - 34, 35 - 44, 45 - 54, 55 - 64, and > 65 years) and adjusted to the age distribution in the 1976 Western Samoan census (18) (Table 1). Table 1. Age distribution of adults, Western Samoan Census both sexes, 1976 Age group Percentage (years) Number distribution 20- 24 12 049 20.4 25-34 14 566 24.6 35-44 12466 21.1 45 - 54 9 832 16.6 55 - 64 5 775 .9.8 > 65 4 497 7.6 Total 59 185 100.0 RESULTS Table 2 shows the crude prevalence rates for IGT and DM for males, females, and combined sexes in the various populations. The age-standardized rates for IGT and DM for the same group are shown in Table 3. Table 2. Prevalence (%) of impaired glucose tolerance (IGT) and diabetes mellitus (DM) in Pacific populations aged ) 20 years (crude rates) Males Females Combined sexes Population group No. No. No. tested IGT DM tested IGT DM tested IGT DM MICRONESIANS Nauru 217 19.4 30.9 239 25.1 29.7 456 22.4 30.3 POLYNESIANS Western Samoa Rural 358 4.2 1.7 387 3.6 4.9 745 3.9 3.4 Urban 325 7.7 8.6 419 8.8 8.8 744 8.3 8.7 Tuvalu 189 9.0 1.1 208 17.8 7.2 397 13.6 4.3 New Caledonia Ouvea" 164 4.9 6.7 237 10.1 7.2 401 8.0 7.0 MELANESIANS New Caledonia Ouvea 228 3.5 0.0 307 6.2 3.9 535 5.0 2.2 Touho 90 6.7 2.2 82 4.9 1.2 172 5.8 1.7 " Mixed with Melanesians 280 NEW CRITERIA FOR DIABETES MELLITUS Table 3. Age standardized prevalence (% ± SE) of impaired glucose tolerance (IGT) and diabetes mellitus (DM) in Pacific populations aged > 20 years Population Males Females Combined sexes group IGT DM IGT DM IGT DM MICRONESIANS Nauru 20.0 ± 2.7 30.0 ± 2.9 25.3 ± 2.9 30.5 ± 2.8 22.7 ± 2.0 30.3 ± 2.0 POLYNESIANS Western Samoa Rural 4.1 ± 1.1 1.3 ± 0.5 3.3 ± 0.9 4.1 + 0.9 3.6 ± 0.7 2.7 ± 0.5 Urban 6.5 ± 1.3 7.1 ± 1.3 8.2 ± 1.3 6.8 ± 1.0 7.6 ± 0.9 7.0 ± 0.8 Tuvalu 7.0 ± 1.7 0.7 ± 0.5 17.5 ± 2.5 8.1 ± 1.9 13.1 ± 1.7 3.9 ± 0.9 New Caledonia Ouvea 4.2 ± 1.4 6.0 ± 1.7 8.5 + 1.8 5.6 ± 1.4 6.6 ± 1.2 5.8 ± 1.1 MELANESIANS New Caledonia Ouvea 2.8 ± 0.9 0.0 6.1 ± 1.4 3.5 ± 1.0 4.6 ± 0.9 2.0 ± 0.6 Touho 4.4 ± 1.7 1.7 ± 1.2 4.1 ± 1.9 1.3 ± 1.2 4.5 ± 1.4 1.5 ± 0.8 DISCUSSION In view of the widespread acceptance of the new diagnostic criteria (6), we felt it worth while to review our data from earlier studies (12 - 16). Despite the use of these new and more stringent criteria, the Micro- nesian population of Nauru show an exceptionally high diabetes prevalence (30.307o) matched only by that reported in the Pima Indians (9, 17). The lowest rate reported here is in the Melanesians of Touho, New Caledonia (1.5%). Low rates are also seen in the rural Western Samoans and the isolated, partly urbanized, Tuvaluan islanders. Intermediate rates (3.4-8.7%) are seen in mixed and pure Poly- nesians. The Nauruans also show the highest prevalence rates of IGT. The rural/urban difference in DM prevalence rate noted in Western Samoans also holds for IGT. However, the significance of IGT has not yet been established and can be determined only by pros- pective studies in these and other populations (4-6). ACKNOWLEDGEMENTS We thank Miss Roma Swan for her help in the preparation of the manuscript and Mr W. Hudson and Ms S. Cesnik for technical assistance. RESUME TAUX DE PREVALENCE DES TROUBLES DE L'HYPERGLYCEMIE PROVOQUEE ET DU DIABETE SUCRE DANS DIVERSES POPULATIONS DU PACIFIQUE EN FONCTION DES NOLIVEAUX CRITERES PROPOSES PAR L'OMS Le Comite d'experts du Diabete de l'Organisation mondiale de la Sante (OMS) a recommande de nouveaux cri- teres diagnostiques pour les epreuves orales d'hypergly- cemie provoquee, dans le but de faciliter une normalisation mondiale et de permettre la comparaison internationale des taux de prevalence du diabete. Dans de precedentes publi- cations sur l'etat de cette question dans plusieurs popula- tions micronesiennes, polynesiennes et melanesiennes de la Region du Pacifique, nous avions utilise les anciens criteres. Notre article actuel sur les taux de prevalence des troubles de 281 282 P. ZIMMET ET AL. I'hyperglycemie provoquee (THP) et du diabete dans ces groupes tient compte des nouveaux criteres. La population micronesienne de Nauru presente les taux de prevalence les plus eleves tant pour les THP (22,7%7o) que pour le diabete (30,30Vo) - 53o de la population adulte montrant des resultats anormaux a l'epreuve d'hyper- glycemie provoquee. Les taux de prevalence les plus faibles pour les THP (4,507o) et le diabete (1,5%) ont et observes dans la population melanesienne rurale de la principale ile de Nouvelle-Caledonie. La presentation sous cette forme de la prevalence des THP et du diabete fournira une base pour la comparaison de nos travaux sur ces populations du Pacifique avec d'autres etudes internationales. REFERENCES 1. ZIMMET, P. Epidemiology of diabetes and its macro- vascular manifestations in Pacific populations. The medical effects of social progress. Diabetes care, 2: 144- 153 (1979). 2. BENNETT, P. H. Recommendations on the standardiz- ation of methods and reporting of tests for diabetes and its microvascular complications in epidemiologic studies. 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