Evidence for low high-density lipoprotein cholesterol levels in Australian indigenous peoples: a systematic review

Background

Low plasma high-density lipoprotein cholesterol (HDL-C) levels are a strong, independent, but poorly understood risk factor for cardiovascular disease (CVD). Although this atherogenic lipid abnormality has been widely reported in Australia’s Indigenous peoples, Aboriginal and Torres Strait Islanders, the evidence has not come under systematic review. This review therefore examines published data for Indigenous Australians reporting 1) mean HDL-C levels for both sexes and 2) factors associated with low HDL-C.

Methods

PubMed, Medline and Informit ATSI Health databases were systematically searched between 1950 and 2012 for studies on Indigenous Australians reporting mean HDL-C levels in both sexes. Retrieved studies were evaluated by standard criteria. Low HDL-C was defined as: <1.0 mmol/L. Analyses of primary data associating measures of HDL-C with other CVD risk factors were also performed.

Results

Fifteen of 93 retrieved studies were identified for inclusion. These provided 58 mean HDL-C levels; 29 for each sex, most obtained in rural/regional (20%) or remote settings (60%) and including 51–1641 participants. For Australian Aborigines, mean HDL-C values ranged between 0.81-1.50 mmol/L in females and 0.76-1.60 mmol/L in males. Two of 15 studies reported HDL-C levels for Torres Strait Islander populations, mean HDL-C: 1.00 or 1.11 mmol/L for females and 1.01 or 1.13 mmol/L for males. Low HDL-C was observed only in rural/regional and remote settings - not in national or urban studies (n = 3) in either gender. Diabetes prevalence, mean/median waist-to-hip ratio and circulating C-reactive protein levels were negatively associated with HDL-C levels (all P < 0.05). Thirty-four per cent of studies reported lower mean HDL-C levels in females than in males.

Conclusions

Very low mean HDL-C levels are common in Australian Indigenous populations living in rural and remote communities. Inverse associations between HDL-C and central obesity, diabetes prevalence and inflammatory markers suggest a particularly adverse CVD risk factor profile. An absence of sex dichotomy in HDL-C levels warrants further investigation.

Racial/ethnic differences in dyslipidemia patterns

BACKGROUND

No studies have comprehensively examined the prevalence of dyslipidemia, a major risk factor for cardiovascular disease, among diverse racial/ethnic minority groups. The primary aim of this study was to identify racial/ethnic differences in dyslipidemia among minorities including Asian Americans (Asian Indian, Chinese, Filipino, Japanese, Korean, or Vietnamese), Mexican Americans, and blacks compared with non-Hispanic whites.

METHODS AND RESULTS

Using a 3-year cross section (2008-2011), we identified 169 430 active primary care patients (35 years or older) from an outpatient healthcare organization in northern California. Age-standardized prevalence rates were calculated for 3 dyslipidemia subtypes: high triglycerides (fasting laboratory value ≥150 mg/dL), low levels of high-density lipoprotein cholesterol (fasting laboratory value <40 mg/dL [men] and <50 mg/dL [women]), and high levels of low-density lipoprotein cholesterol (fasting laboratory value ≥130 mg/dL or taking low-density lipoprotein-lowering agents). Odds ratios were calculated by multivariable logistic regression, with adjustment for patient characteristics (age, measured body mass index, smoking). Compared with non-Hispanic whites, every minority subgroup had an increased prevalence of high triglycerides except blacks. Most minority groups had an increased prevalence of low high-density lipoprotein cholesterol, except for Japanese and blacks. The prevalence of high low-density lipoprotein cholesterol was increased among Asian Indians, Filipinos, Japanese, and Vietnamese compared with non-Hispanic whites.

CONCLUSIONS

Minority groups, except for blacks, were more likely to have high triglyceride/low high-density lipoprotein cholesterol dyslipidemia. Further research is needed to determine how racial/ethnic differences in dyslipidemia affect racial/ethnic differences in cardiovascular disease rates.

Obesity and dyslipidemia in South Asians

Obesity and dyslipidemia are emerging as major public health challenges in South Asian countries. The prevalence of obesity is more in urban areas than rural, and women are more affected than men. Further, obesity in childhood and adolescents is rising rapidly. Obesity in South Asians has characteristic features: high prevalence of abdominal obesity, with more intra-abdominal and truncal subcutaneous adiposity than white Caucasians. In addition, there is greater accumulation of fat at “ectopic” sites, namely the liver and skeletal muscles. All these features lead to higher magnitude of insulin resistance, and its concomitant metabolic disorders (the metabolic syndrome) including atherogenic dyslipidemia. Because of the occurrence of type 2 diabetes, dyslipidemia and other cardiovascular morbidities at a lower range of body mass index (BMI) and waist circumference (WC), it is proposed that cut-offs for both measures of obesity should be lower (BMI 23–24.9 kg/m² for overweight and ≥25 kg/m² for obesity, WC ≥80 cm for women and ≥90 cm for men for abdominal obesity) for South Asians, and a consensus guideline for these revised measures has been developed for Asian Indians. Increasing obesity and dyslipidemia in South Asians is primarily driven by nutrition, lifestyle and demographic transitions, increasingly faulty diets and physical inactivity, in the background of genetic predisposition. Dietary guidelines for prevention of obesity and diabetes, and physical activity guidelines for Asian Indians are now available. Intervention programs with emphasis on improving knowledge, attitude and practices regarding healthy nutrition, physical activity and stress management need to be implemented. Evidence for successful intervention program for prevention of childhood obesity and for prevention of diabetes is available for Asian Indians, and could be applied to all South Asian countries with similar cultural and lifestyle profiles. Finally, more research on pathophysiology, guidelines for cut-offs, and culturally-specific lifestyle management of obesity, dyslipidemia and the metabolic syndrome are needed for South Asians.

A systematic review of overweight, obesity, and type 2 diabetes among Asian American subgroups

This systematic review synthesizes data published between 1988 and 2009 on mean BMI and prevalence of overweight, obesity, and type 2 diabetes among Asian subgroups in the U.S. We conducted systematic searches in Pub- Med for peer-reviewed, English-language citations that reported mean BMI and percent overweight, obesity, and diabetes among South Asians/Asian Indians, Chinese, Filipinos, Koreans, and Vietnamese. We identified 647 database citations and 23 additional citations from hand-searching. After screening titles, abstracts, and full-text publications, 97 citations remained. None were published between 1988 and 1992, 28 between 1993 and 2003, and 69 between 2004 and 2009. Publications were identified for the following Asian subgroups: South Asian (n=8), Asian Indian (n=20), Chinese (n=44), Filipino (n=22), Korean (n= 8), and Vietnamese (n=3). The observed sample sizes ranged from 32 to 4245 subjects with mean ages from 24 to 78 years. Among samples of men and women, the lowest reported mean BMI was in South Asians (22.1 kg/m(2)), and the highest was in Filipinos (26.8 kg/m(2)). Estimates for overweight (12.8-46.7%) and obesity (2.1-59.0%) were variable. Among men and women, the highest rate of diabetes was reported in Asian Indians with BMI ≥ 30 kg/m(2) (32.9%, age and sex standardized). This review suggests heterogeneity among U.S. Asian populations in cardiometabolic risk factors, yet comparisons are limited due to variability in study populations, methods, and definitions used in published reports. Future efforts should adopt standardized methods to understand overweight, obesity and diabetes in this growing U.S. ethnic population.

Fat distribution and insulin resistance in young adult nonobese Asian Indian women

Although Asian Indian (people of Indian subcontinent descent) men are shown to have higher total and truncal body fat as well as greater insulin resistance compared to white men matched for total body fat and age, data in women are not conclusive. The objective of this study was to compare total and regional fat distribution and insulin sensitivity between healthy young premenopausal Asian Indian and white women of similar body mass index (BMI). Twenty Asian Indian women (65% immigrants and 35% first generation living in Dallas) and 31 white women of similar age and BMI [age 24±3 vs. 25±4; BMI 22±4 vs. 23±5; mean±standard deviation (SD) in Asian Indian and white, respectively] without diabetes were evaluated with anthropometric measurements, underwater weighing for percentage of total body fat mass, magnetic resonance imaging of whole abdomen for measurement of abdominal subcutaneous and intraperitoneal fat mass, and euglycemic-hyperinsulinemic clamp study for measurement of insulin sensitivity. There were no differences in waist or hip circumference, total body subcutaneous abdominal or intraperitoneal fat mass, fasting plasma glucose, and insulin levels between Asian Indian women and white women. The peripheral glucose disposal rate (Rd) during hyperinsulinemic-euglycemic clamp was found to be almost identical in the two study groups (median value of 6.9 and 6.8 mg/min per kg of body weight, for Asian Indians and whites, respectively). For similar total or regional fat content, the glucose disposal rate was comparable in the two study groups. In conclusion, we demonstrate that young Asian Indian women do not have excess abdominal or intraperitoneal fat or insulin resistance for similar BMI compared to white women of European descent.

Impact of body mass index levels on lipid abnormalities in Chinese Asians, American Blacks and American Whites: the People's Republic of China (PRC) and Atherosclerosis Risk in Communities (ARIC) Studies

BACKGROUND

Several researchers have reported that Chinese adults may have a greater chronic disease burden than Whites, especially at lower body mass index (BMI) levels.

OBJECTIVES

To compare the incidence of lipid abnormalities in Chinese (n=5303), White (n=10,752) and Black (n=3408) middle-aged adults and the effect of BMI on these incidences.

METHODS

Data were from the People's Republic of China (PRC) and the Atherosclerosis Risk in Communities (ARIC) studies. In each ethnic group, we calculated the adjusted cumulative incidence for high total cholesterol (≥240mg/dL), LDL-cholesterol (≥160mg/dL), and triglycerides (≥200mg/dL) and low HDL-cholesterol (≤40 in men and ≤50mg/dL in women) adjusted for age, gender, education, field site, smoking and drinking status. Risk differences associated with BMI (referent=18.5-22.9kg/m(2)) were calculated using weighted linear regression and slopes compared using the Wald test.

RESULTS

Chinese had lower incidence of abnormal total cholesterol, LDL-cholesterol and triglycerides than Whites in most BMI groups and had lower incidence of abnormal HDL-cholesterol and triglycerides than Blacks. Across the range of 18.5 to <30, BMI was more strongly associated with the incidence of having high total cholesterol in Chinese and Whites than in Blacks. Similar trends were seen for LDL-cholesterol and triglycerides, but were not always statistically significant. In contrast, BMI was more highly associated with incidence of low HDL-cholesterol in Whites than in Chinese or Blacks.

CONCLUSION

Although differences in the incidence of lipid abnormalities and the impact of BMI were identified, results varied by lipid type indicating no consistent ethnic/national pattern.

Decreased high-density lipoprotein cholesterol levels in polyarticular juvenile idiopathic arthritis

OBJECTIVES

To investigate the prevalence of dyslipoproteinemia in a homogeneous cohort of polyarticular juvenile idiopathic arthritis patients.

METHODS

Based on the National Cholesterol Education Program, fasting lipoprotein levels and risk levels for coronary artery disease were determined in 28 patients with polyarticular juvenile idiopathic arthritis. The exclusion criteria included diabetes, thyroid dysfunction, smoking, proteinuria, lipid-lowering drugs, and hormone/diuretic therapy. Disease activity, disease duration, and therapy with corticosteroids and/or chloroquine were defined at the time of lipid measurements.

RESULTS

Dyslipoproteinemia was identified in 20 of the 28 (71%) patients with polyarticular juvenile idiopathic arthritis. The primary lipoprotein risk factor was decreased high-density lipoprotein cholesterol (57%), followed by elevated levels of low-density lipoprotein cholesterol (18%), triglycerides (14%), and total cholesterol (7%). The male patients had decreased high-density lipoprotein cholesterol levels than the female patients (p<0.05). The incidence of decreased high-density lipoprotein cholesterol levels did not seem to be affected by disease activity or therapy because the incidence was similar in patients with active or inactive disease, with or without corticosteroid use and with or without chloroquine use. In addition, the frequency of decreased high-density lipoprotein cholesterol levels was similar in patients with short (≤5 years) vs. long (>5 years) disease duration.

CONCLUSIONS

Dyslipoproteinemia is highly prevalent in patients with polyarticular juvenile idiopathic arthritis and is primarily related to decreased high-density lipoprotein cholesterol levels; therefore, early intervention is essential.

Obesity-related non-communicable diseases: South Asians vs White Caucasians

South Asians are at higher risk than White Caucasians for the development of obesity and obesity-related non-communicable diseases (OR-NCDs), including insulin resistance, the metabolic syndrome, type 2 diabetes mellitus (T2DM) and coronary heart disease (CHD). Rapid nutrition and lifestyle transitions have contributed to acceleration of OR-NCDs in South Asians. Differences in determinants and associated factors for OR-NCDs between South Asians and White Caucasians include body phenotype (high body fat, high truncal, subcutaneous and intra-abdominal fat, and low muscle mass), biochemical parameters (hyperinsulinemia, hyperglycemia, dyslipidemia, hyperleptinemia, low levels of adiponectin and high levels of C-reactive protein), procoagulant state and endothelial dysfunction. Higher prevalence, earlier onset and increased complications of T2DM and CHD are often seen at lower levels of body mass index (BMI) and waist circumference (WC) in South Asians than White Caucasians. In view of these data, lower cut-offs for obesity and abdominal obesity have been advocated for Asian Indians (BMI; overweight >23 to 24.9 kg m(-2) and obesity ≥ 25 kg m(-2); and WC; men ≥ 90 cm and women ≥ 80 cm, respectively). Imbalanced nutrition, physical inactivity, perinatal adverse events and genetic differences are also important contributory factors. Other differences between South Asians and White Caucasians include lower disease awareness and health-seeking behavior, delayed diagnosis due to atypical presentation and language barriers, and religious and sociocultural factors. All these factors result in poorer prevention, less aggressive therapy, poorer response to medical and surgical interventions, and higher morbidity and mortality in the former. Finally, differences in response to pharmacological agents may exist between South Asians and White Caucasians, although these have been inadequately studied. In view of these data, prevention and management strategies should be more aggressive for South Asians for more positive health outcomes. Finally, lower cut-offs of obesity and abdominal obesity for South Asians are expected to help physicians in better and more effective prevention of OR-NCDs.

Distinct ethnic differences in lipid profiles across glucose categories

CONTEXT

Dyslipidemia coexists with hyperglycemia. However, little is known about the ethnic differences in lipid profiles at comparable glucose tolerance status.

OBJECTIVE

The aim was to study ethnic differences in lipid profiles stratified by glucose levels.

DESIGN AND SETTING

Data from 31 study cohorts of 12 countries, consisting of 24,760 men and 27,595 women aged 25-74 yr, were compared. The odds ratio for having dyslipidemia was estimated for each ethnic group stratified by glucose categories.

RESULTS

Compared with central and northern Europeans, multivariable adjusted odds ratios (95% confidence intervals) for having lower high-density lipoprotein-cholesterol were 4.74 (4.19-5.37), 5.05 (3.88-6.56), 3.07 (2.15-4.40), and 2.37 (1.67-3.35) in Asian Indian men, but 0.12 (0.09-0.16), 0.07 (0.04-0.13), 0.11 (0.07-0.20), and 0.16 (0.08-0.32) in Chinese men who had normoglycemia, prediabetes, and undiagnosed and diagnosed diabetes, respectively. Similar results were obtained for women. The prevalence of low high-density lipoprotein-cholesterol remained higher in Asian Indians (62.8% of the nondiabetic and 67.4% of the diabetic) than in central and northern Europeans (20.3 and 37.3%), Japanese (25.7 and 34.1%), or Qingdao Chinese (15.7 and 17.0%), even in individuals with low-density lipoprotein-cholesterol of less than 3 mmol/liter.

CONCLUSION

There are distinct patterns of lipid profiles associated with ethnicity regardless of the glucose levels, suggesting that ethnic-specific strategies and guidelines on risk assessment and prevention of cardiovascular disease are required.

Blood lipid levels in relation to glucose status in seven populations of Asian origin without a prior history of diabetes: the DECODA study

BACKGROUND

Dyslipidaemia commonly coexists with diabetes. We investigated the association of lipid profiles with glucose levels in populations of Asian origin without a prior history of diabetes.

METHODS

Cross-sectional data of 10,374 men and 12,552 women aged 30-74 years from 14 cohorts, representing seven populations of Asian origin were jointly analysed. Multivariable adjusted linear regression analyses with standardized regression coefficients (beta) were performed to estimate relationships between lipids and plasma glucose.

RESULTS

Within each glucose category, fasting plasma glucose (FPG) levels were correlated with increasing levels of triglycerides (TGs), total cholesterol (TC), TC to high-density lipoprotein (HDL) ratio and non-HDL cholesterol (non-HDL-C) (p < 0.05 in most of the ethnic groups) and inversely associated with HDL-C (p < 0.05 in some, but not all, of the populations). The association of lipids with 2-h plasma glucose (2hPG) followed a similar pattern as that for the FPG, except that an inverse relationship between HDL-C and glucose was more commonly observed for 2hPG than for FPG among different ethnic groups.

CONCLUSIONS

Hyperglycaemia is associated with adverse lipid profiles in Asians without a prior history of diabetes. The 2hPG appears to be more closely associated with lipid profiles than does FPG. When assessing the risk of cardiovascular disease, the association of the dyslipidaemia with intermediate hyperglycaemia needs to be considered.