Prevalence of diabetes, metabolic syndrome, and cardiovascular risk factors in US Asian Indians: results from a national study

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Abstract

Background

Although studies of immigrant Asian Indians in other countries show high rates of diabetes (DM), metabolic syndrome (MetS), and cardiovascular disease (CVD), no randomized, population-based studies of this rapidly growing ethnic group exist in the US.

Methods

The sample comprised 1038 randomly selected Asian Indian immigrants, aged 18 years and older at seven US sites. Prevalence of diabetes and MetS (age-adjusted and sex-adjusted means) was estimated and ANOVA was used to calculate gender and group differences (normoglycemia/impaired fasting glucose/diabetes) for CVD risk factors.

Results

The mean age was 48.2 years. The majority of respondents were male, married, educated, and with some form of health insurance. Prevalence of diabetes was 17.4%, and 33% of the respondents had prediabetes. Cardiovascular risk factors, especially high levels of triglycerides, total cholesterol, LDL cholesterol, homocysteine, and C-reactive protein, and low levels of HDL cholesterol, were also prevalent; elevated lipoprotein(a) was not observed. The age-adjusted prevalence of MetS was 26.9% by the original NCEP/ATP III criteria, 32.7% by the modified NCEP/ATP III criteria, and 38.2% by the IDF criteria. The MetS rates for women, but not for men, increased with age using all three criteria. There was a progressive worsening of all metabolic parameters as individuals progressed from normal to IFG to diabetes.

Conclusion

The prevalence rates of diabetes and MetS among US Asian Indians are higher than reported in earlier, nonrandomized, smaller surveys. These data provide a firm basis for future mechanistic and interventional studies.

Introduction

Migrant Asian Indians are reported to have high rates of diabetes (DM), metabolic syndrome (MetS), cardiovascular disease (CVD), and related complications in the US, Canada, and UK (Anand et al., 2000, Chandie Shaw et al., 2002, Enas et al., 1996, Hughes et al., 1997, McKeigue et al., 1993, McKeigue et al., 1992, Mohanty et al., 2005, Omar et al., 1985, Ramaiya et al., 1995, Samanta et al., 1991). Insulin resistance is highly prevalent in Asian Indian migrants, despite low rates of obesity (McKeigue, 1996, McKeigue et al., 1992, Whincup et al., 2002). In the United States, Asian Indians have the highest ethnic-specific prevalence of CVD, with age-specific mortality two to three times higher than Caucasians (Enas & Senthilkumar, 2001, Enas et al., 1996, Wild et al., 1995). Traditional risk factors such as hypertension, obesity, and hypercholesterolemia do not account completely for these high rates. Prevalence of DM and related conditions among US Asian Indians was assessed by Venkataraman et al. (2004) using a faith-based sample in Atlanta, GA. The overall prevalence of DM was 18.3% (22.5% in men and 13.6% in women). Mohanty et al. (2005) compared 555 Asian Indians to 87,846 non-Hispanic whites in the NHIS dataset from 1997 to 2000 and reported that the former had significantly higher odds of having diabetes. However, they also reported lower CHD and hypertension rates, in contrast to prior studies that showed much higher age-standardized CVD rates and related mortality in this ethnic group. Data from national surveys are limited due to small sample sizes or aggregation of ethnic data into a heterogeneous group of “Asian Americans” or “Asian and Pacific Islanders.” Population-based national studies on prevalence and risk factors for DM and CVD among US Asian Indians are currently lacking.

Asian Indians, the third largest and fastest growing US Asian subgroup, are heterogeneous, with numerous languages, religions, racial types, social habits, cultural practices, and diets. Despite a perception that they have high socio-economic status and good access to health care (Gupta, 2000), US Asian Indians have marked variations in educational attainment, income, and wealth, and a significant number lack education and job skills (Rangaswamy, 1995). Recent immigrant cohorts comprise both highly educated professionals and individuals who lack education and job skills. The latter are mostly family members of earlier immigrants (Rangaswamy, 1995). This heterogeneity makes it imperative to use large, randomized samples to determine disease prevalence and risk factors. Previous studies of Asian Indian health have employed hospital-based or convenience samples (Abate et al., 1995, 1996, 2004; Banerji et al., 1999; Enas et al., 1996; Raji, Seely et al., 2001; Raji, Williams et al., 2001; Venkataraman et al., 2004). The Diabetes among Indian Americans (DIA) study is the first to develop and utilize a large, randomly selected, nationwide cohort of US Asian Indians to determine the prevalence of DM, MetS, and CVD risk factors.

Section snippets

Subjects

Asian Indian adults were randomly selected at seven US urban sites—Houston, TX; Phoenix, AZ; Washington, DC; Boston, MA; San Diego, CA; Edison, NJ; and Parsippany, NJ. There is no directory/sampling frame available for Asian Indians in the US; hence directories were created at each site through compilations of several sources: (1) city-wide telephone directories with a search for the 100 most common Asian Indian last names, (2) directories of ethnic associations (e.g., Gujarati Association,

Demographic, dietary, and socioeconomic characteristics

The mean age of the subjects was 45.7±12.8 years (mean±S.D.) with a range of 19–91 years. The majority were male (61%), married (91%), employed (58%), and with some form of health insurance (85%). The modal income was $50,000 to $100,000; 12% reported income below $25,000.00. Mean length of residence in the US was 18.5±11.04 years, and 1.6% were born in the US. Fifty-seven percent reported a family history of diabetes and 6.6% were current smokers (predominantly male).

The majority of the

Discussion

These results from the first randomly selected, population-based study of Asian Indians in the US indicate a very high prevalence of diabetes, prediabetes, and MetS. The prevalence of DM for adults aged ≥20 years (17.4%) exceeds that of non-Hispanic whites (NHW) (7.8%), non-Hispanic blacks (13%), Hispanic Latinos (10.2%), and Native Americans/Alaskan natives (15.1%) as reported by the American Diabetes Association and Centers for Disease Control in 2001 (Fig. 1A). The gender disparity in DM

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