The metabolic syndrome describes the clustering of risk factors for diabetes and cardiovascular disease (1). New Zealand Polynesians of both Maori and Pacific descent have high rates of conponents for the metabolic syndrome: type 2 diabetes (2), obesity (2), hypertension (3), dyslipidemia (4), and coronary heart disease (5,6). There have been no previous reports of the prevalence of the metabolic syndrome in New Zealand since the release of the Adult Treatment Panel (ATP) III criteria (7). In this study, we compare the prevalence of the metabolic syndrome by ATP III criteria among New Zealanders of European and Polynesian descent.

Residents from a household census in South Auckland were randomly selected using a sampling framework stratified by age, sex, and ethnic group as previously described (2). At each house, questionnaires were completed; weight, height, and waist were measured; and a random venous sample was taken for glucose measurement (into fluoride; spun, chilled, and assayed within 3 h). Those without known diabetes and either a random glucose ≥6.5 mmol/l within 2 h of a meal or ≥6 mmol/l ≥2 h after a meal (defined as “screen positives”), as well as a random control group (28% of other subjects; defined as “screen negatives”) were invited for a 75-g oral glucose tolerance test (OGTT). At the OGTT, fasting samples were also taken for lipids (total, HDL, and LDL cholesterol and triglycerides) and measured on a Hitachi 747 analyzer (Hitachi, Tokyo, Japan) (interassay coefficient of variation 2.2, 4.8, and 3.3%, respectively, except LDL cholesterol, which was calculated using the Friedewald equation). Resting blood pressure was taken as the mean of two measurements using a standard mercury sphygmomanometer (with large cuff where necessary) following a standardized approach and before the 2-h glucose sampling.

The ATP III criteria (2) for the metabolic syndrome were considered to have been met when three or more of the following factors were present: waist circumference >102 cm for men or >88 cm for women, elevated blood pressure (treated hypertension or systolic blood pressure ≥130 mmHg and/or diastolic blood pressure ≥85 mmHg as mean of two readings), elevated triglycerides (≥1.7 mmol/l), decreased HDL (<1.04 mmol/l for men or <1.29 mmol/l for women), elevated fasting glucose (≥6.1 mmol/l), or diabetes. The study was approved by the University of Auckland Ethics Committee, and subjects gave informed consent.

Randomization and statistics were undertaken using SPSS for Windows (version 12.0; SPSS, Chicago IL). Comparisons of proportions were made using the χ2 test. Calculations of the prevalence of each constituent of the metabolic syndrome by ATP III criteria and overall were made by direct standardization to the proportion of subjects who were screen negative or positive with Excel 2000 (Microsoft) as follows: (screen positive with characteristic at OGTT) × (% screened who were screen positive)/screen positive attending OGTT + (screen negative with characteristic at OGTT) × (% screened who were screen negative)/screen negative attending OGTT.

As previously reported, the initial household survey had a 91% response with 2,737 interviewed, of whom 314 had known diabetes. Of the 2,423 invited to participate without known diabetes, 1,562 (64.5%) were screened in their home. Subsequent attendance at OGTT was 68.4% (327 of 478) among screen-positive and 67.2% (207 of 308 invited) among screen-negative subjects. Mean age was 50 ± 5 (Europeans), 49 ± 5 (Maori), and 49 ± 5 years (Pacific) (P = 0.029) in the 40- to 59-year age-group and 68 ± 6, 66 ± 5, and 67 ± 5 years, respectively, in the 60- to 79-year age-group (P < 0.001).

The prevalence of known diabetes, obesity, and low HDL was significantly higher among Polynesians in both age-groups (Table 1). Maori, but not Pacific, subjects consistently had a higher blood pressure, although this difference was not significant among women aged 60–79 years. The prevalence of hypertriglyceridemia was highest among Maori and Pacific people, except among women aged 40–59 years. The presence of an elevated fasting glucose or new diabetes diagnosis was significantly more likely among Maori and Pacific women aged 40–59 years and nonsignificantly higher among men of these ethnic groups.

Among those aged 40–59 years, a very small proportion of Maori and Pacific subjects showed no components of the metabolic syndrome and a much higher proportion (approximately half) had three or more components, making them eligible for metabolic syndrome diagnosis. Among those aged 60–79 years, there was no significant difference in the overall distribution of the components or prevalence of the metabolic syndrome among women (P = 0.350). The prevalence of the metabolic syndrome was higher among men (P = 0.005).

Among Maori and Pacific peoples aged ≥40 years, the total prevalence of the metabolic syndrome and known diabetes was >50%, with ∼80% having at least two components of the metabolic syndrome (also associated with a significantly increased risk of cardiovascular disease [8]). The prevalence of the metabolic syndrome by ATP III criteria among men of European descent aged ≥40 years has been reported to range from 12% across the eight DECODE (Diabetes Epidemiology: Collaborative Analysis of Diagnostic Criteria in Europe) studies (8), to 28.8% (35–75 years) in Canada (9), and to 30–40% in the U.S. (10). These New Zealand data are clearly most comparable to those in North America. Among women of European descent in Canada aged 35–75 years, the prevalence of the metabolic syndrome was 14.3% (9), and in Europe, the prevalence increased from 5.2% among those aged 40–49 years to 16.8% among those aged ≥70 years (8). In the U.S., the prevalence of the metabolic syndrome increased from ∼19% among women aged 40–49 years to a peak of ∼45% in those aged 70–79 years (10). There have been no reports of the prevalence of the metabolic syndrome among Polynesians elsewhere, but the age-specific prevalences among Maori and Pacific people were comparable to Mexican Americans (10,11), Arab Americans (12), and Native Americans (9,13) but higher than those among South Asians (9), East Asians (9,14,15), and African Americans (10).

These findings are limited by the small numbers in each stratum and the stratified nature of the attendance at OGTT, and this probably explains the lack of statistical significance for some components (e.g., new diabetes). The criteria for obesity are also an issue among Polynesians (16).

Table 1—

Prevalence of the metabolic syndrome by ATP III criteria (three or more items) and its components

Men
Women
EuropeanMaoriPacific IslanderPEuropeanMaoriPacific IslanderP
Aged 40–59 years         
    Known diabetes 17/276 (6.2%) 29/239 (12.1%) 45/338 (13.3%) 0.012 9/315 (2.9%) 40/350 (11.4%) 53/410 (12.9%) <0.001 
    Known hypertension 30/191 (15.7%) 32/157 (20.4%) 39/231 (16.9%) 0.499 27/238 (11.3%) 55/242 (22.7%) 46/302 (15.2%) 0.003 
    BMI >30 kg/m2 (%) 28.6 72.4 71.6 <0.001 34.7 64.3 81.6 <0.001 
    High waist circumference (%) 36.2 63.9 66.4 <0.001 41.8 75.2 91.8 <0.001 
    OGTT attenders (n)* 38 41 66  48 69 98  
    High blood pressure (%) 54.6 81.5 72.3 0.042 45.4 74.0 58.6 0.008 
    Triglycerides ≥1.7 mmol/l (%) 37.6 58.3 69.4 0.005 42.6 40.0 31.9 0.361 
    Decreased HDL (%) 32.1 63.5 53.9 0.014 45.2 76.7 66.8 0.002 
    Hyperglycemia (%) 13.3 36.4 30.2 0.053 8.6 12.2 28.2 0.002 
    ATP III items (%)    0.004    <0.001 
        None 31.6 5.9 8.4  19.0 8.0 8.6 
    0    One 19.9 13.1 12.3  26.3 6.7 12.6 
        Two 23.7 28.2 30.8  41.3 33.5 33.3 
        Three or more 24.6 52.8 48.5  13.4 51.8 45.5 
Aged 60–79 years         
    Known diabetes 12/158 (7.6%) 15/94 (16.0%) 31/138 (22.5%) 0.002 18/187 (9.7%) 16/97 (16.5%) 29/135 (21.6%) 0.012 
    Known hypertension 31/120 (25.8%) 22/60 (36.7%) 28/106 (26.4%) 0.271 47/140 (33.6%) 25/70 (35.7%) 24/101 (23.8%) 0.162 
    BMI >30 kg/m2 (%) 20.2 58.9 52.2 <0.001 32.0 60.0 69.5 <0.001 
    High waist circumference (%) 36.9 56.4 53.2 0.022 52.8 76.2 91.6 <0.001 
    OGTT attenders (n)* 37 16 28  48 19 27  
    High blood pressure (%) 77.2 92.3 54.7 0.009 78.7 81.5 67.0 0.447 
    Triglycerides ≥1.7 mmol/l (%) 21.4 61.2 45.5 0.011 27.8 45.4 44.1 0.170 
    Decreased HDL (%) 31.2 67.0 65.4 0.011 19.8 52.6 59.9 0.002 
    Hyperglycemia (%) 18.9 48.8 25.5 0.062 19.5 21.0 17.4 0.972 
    ATP III items (%)    0.087    0.465 
        None 13.9 7.7 10.9  7.2 9.3 5.8 
        One 26.5 12.8 23.6  31.4 18.1 11.5 
        Two 37.9 12.8 25.5  30.4 27.3 38.8 
        Three or more 21.7 66.7 39.9  31.0 45.4 43.9 
Men
Women
EuropeanMaoriPacific IslanderPEuropeanMaoriPacific IslanderP
Aged 40–59 years         
    Known diabetes 17/276 (6.2%) 29/239 (12.1%) 45/338 (13.3%) 0.012 9/315 (2.9%) 40/350 (11.4%) 53/410 (12.9%) <0.001 
    Known hypertension 30/191 (15.7%) 32/157 (20.4%) 39/231 (16.9%) 0.499 27/238 (11.3%) 55/242 (22.7%) 46/302 (15.2%) 0.003 
    BMI >30 kg/m2 (%) 28.6 72.4 71.6 <0.001 34.7 64.3 81.6 <0.001 
    High waist circumference (%) 36.2 63.9 66.4 <0.001 41.8 75.2 91.8 <0.001 
    OGTT attenders (n)* 38 41 66  48 69 98  
    High blood pressure (%) 54.6 81.5 72.3 0.042 45.4 74.0 58.6 0.008 
    Triglycerides ≥1.7 mmol/l (%) 37.6 58.3 69.4 0.005 42.6 40.0 31.9 0.361 
    Decreased HDL (%) 32.1 63.5 53.9 0.014 45.2 76.7 66.8 0.002 
    Hyperglycemia (%) 13.3 36.4 30.2 0.053 8.6 12.2 28.2 0.002 
    ATP III items (%)    0.004    <0.001 
        None 31.6 5.9 8.4  19.0 8.0 8.6 
    0    One 19.9 13.1 12.3  26.3 6.7 12.6 
        Two 23.7 28.2 30.8  41.3 33.5 33.3 
        Three or more 24.6 52.8 48.5  13.4 51.8 45.5 
Aged 60–79 years         
    Known diabetes 12/158 (7.6%) 15/94 (16.0%) 31/138 (22.5%) 0.002 18/187 (9.7%) 16/97 (16.5%) 29/135 (21.6%) 0.012 
    Known hypertension 31/120 (25.8%) 22/60 (36.7%) 28/106 (26.4%) 0.271 47/140 (33.6%) 25/70 (35.7%) 24/101 (23.8%) 0.162 
    BMI >30 kg/m2 (%) 20.2 58.9 52.2 <0.001 32.0 60.0 69.5 <0.001 
    High waist circumference (%) 36.9 56.4 53.2 0.022 52.8 76.2 91.6 <0.001 
    OGTT attenders (n)* 37 16 28  48 19 27  
    High blood pressure (%) 77.2 92.3 54.7 0.009 78.7 81.5 67.0 0.447 
    Triglycerides ≥1.7 mmol/l (%) 21.4 61.2 45.5 0.011 27.8 45.4 44.1 0.170 
    Decreased HDL (%) 31.2 67.0 65.4 0.011 19.8 52.6 59.9 0.002 
    Hyperglycemia (%) 18.9 48.8 25.5 0.062 19.5 21.0 17.4 0.972 
    ATP III items (%)    0.087    0.465 
        None 13.9 7.7 10.9  7.2 9.3 5.8 
        One 26.5 12.8 23.6  31.4 18.1 11.5 
        Two 37.9 12.8 25.5  30.4 27.3 38.8 
        Three or more 21.7 66.7 39.9  31.0 45.4 43.9 

Due to rounding, percentages may not total exactly 100%. High waist circumference: >102 cm for men and >88 cm for women; high blood pressure: ≥130/85 mmHg or known hypertension; hyperglycemia: new diabetes or fasting blood glucose ≥6.1 mmol/l; decreased HDL: HDL <1.04 mmol/l for men and <1.29 mmol/l for women.

*

OGTT attenders: data adjusted for the proportion who were screen positive and screen negative by direct standardization.

The authors thank Servier for funding a research fellow (C.F.T.) and the Auckland Medical Research Foundation, the Maurice and Phyllis Paykel Trust, the Hector Trust, and SmithKline Beecham for contributions to the research funding.

The authors also thank members of the Diabetes Projects Trust for their assistance.

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A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.