Adiposity measures and their validity in estimating risk of hypertension in South Asian children: a cross-sectional study.

OBJECTIVE: Given the South Asian phenotype of higher body fat at similar body mass index (BMI) relative to Caucasians, we sought to explore the association between prominent adiposity indicators with blood pressure (BP) and hypertension, to compare the accuracy of these indicators in estimating hypertension, and to provide cut-off values associated with adverse hypertension risk in South Asian children. DESIGN: Cross-sectional study. SETTING: Community-based recruitment in two Canadian cities (Hamilton and Surrey). PARTICIPANTS: South Asian children (n=762) were recruited from two Canadian cities. Waist circumference, waist to height ratio and BMI were determined. Body fat percentage was assessed by bioelectrical impedance analysis and BP was assessed using an automated device. All variables (except body fat percentage) were transformed to z-scores using published standards. OUTCOME MEASURES: Linear and Poisson regression was used to explore associations between the adiposity indicators with BP z-score and hypertension. Receiver operating curve (ROC) analysis was used to explore the strength of the adiposity indicators in estimating hypertension risk and sex-stratified optimal adiposity cut-off values associated with hypertension risk. RESULTS: Significant associations were detected in adjusted and unadjusted models between the adiposity indicators with BP z-score and hypertension (p<0.01 for all). The area under the curve (AUC) values for the adiposity indicators for boys and girls ranged from 0.74 to 0.80, suggesting that the adiposity indicators are fair measures of estimating hypertension risk. Sex-stratified cut-off associated with adverse risk of hypertension for girls and boys, respectively, were at the 92nd and 82nd percentile for BMI z-scores, 65th and 80th percentile for WC z-score, 63rd and 67th percentile for WHtR z-score and at 29.8% and 23.5% for body fat. CONCLUSION: Our results show associations between adiposity indicators with BP and hypertension and suggests that South Asian children might be at adverse risk of hypertension at levels of adiposity considered normal.

The predictive relationship between baseline insulin and glucose with subclinical carotid atherosclerosis after 5 years in a multi-ethnic cohort.

BACKGROUND AND AIMS: We aimed at exploring the relationship between baseline insulin and glucose and the progression of carotid atherosclerosis in a multi-ethnic cohort. METHODS: Males and females (n = 797) of European, Chinese, South Asian and Aboriginal origin were assessed as part of the Multicultural Community Health Assessment Trial (MCHAT) study for socio-demographics, smoking status, fasting insulin and glucose at baseline. IMT, plaque area and total area were assessed after 5 years. RESULTS: A total of 545 participants returned after 5 years for a follow-up assessment. Average age of the study participants was 47.5 (SD 8.9) years. At baseline, the median and interquartile range for insulin was 62.0 (49.5) pmol/L, and glucose was 5.2 (0.60) mmol/L. Baseline glucose and insulin predicted the 5-year progression of atherosclerosis in our models, after adjusting for covariates. We found significant insulin-ethnicity interactions in the IMT model (p = 0.044) with the slope of the relationship showing that for every percentage change in insulin the Europeans experienced 7.3% more increase in IMT at 5 years than the Aboriginals. In the plaque area and total area models, there were significant glucose-ethnicity interactions (p = 0.009 and p=0.016 respectively), with the slope showing a 101% and 121% increase for plaque area and total area, respectively, in Europeans, at 5 years per percent change in glucose at baseline. Logistic regression found a significant glucose-ethnicity interaction with the presence of plaques (OR = 0.31, p = 0.03) such that compared to the Europeans, the South Asians had a lower odds of developing plaque presence. Similarly, we found glucose-ethnicity interactions in the logistic regression when comparing the Chinese to the Europeans (OR = 0.2, p=0.005), with the Chinese being less likely to develop plaque presence. CONCLUSIONS: Ethnicity modifies the predictive relationship between insulin and glucose with sub-clinical indicators of carotid atherosclerosis but not consistently so.