The development of cardiovascular disease in relation to anthropometric indices and hypertension in British adults.

OBJECTIVE

To examine the predictive ability of simple anthropometric indices for the development of cardiovascular disease (CVD) over seven years in British adults, and the influence of hypertension on these associations.

DESIGN

Longitudinal study of the development of CVD (morbidity or mortality) over a seven year period in a random stratified sample of British adults who were respondents in the 1984-1985 Health and Lifestyle Survey (HALS1) and who were seen again in 1991-1992 (HALS2) or who had died by then.

METHODS

Face-to-face interviews at HALS1 and HALS2 recorded socio-demographic, health and lifestyle details followed by measurements of height, weight, waist circumference and blood pressure (BP). The quintiles of body mass index (BMI), waist circumference, waist: height ratio (WHTR) and height were calculated for those aged between 35 and 75 y, at HALS1. Dates and causes of death were recorded. Logistic regression was used to estimate the odds ratios (OR) of developing CVD in 1284 men and 1570 women, aged 35-75 y who were free of known CVD, cancer and diabetes at HALS1.

RESULTS

By HALS2, 316 respondents in the qualifying population had developed CVD, 114 of whom were dead. There were linear trends in the development of CVD (adjusted for age and smoking) for all the men from the lowest to the highest quintile of WHTR (P = 0.034), but not for waist circumference (P = 0.095), or BMI (P > 0.2). Excluding the hypertensive men increased the significance of the trend for WHTR (P = 0.005) and waist circumference (P = 0.027). The significant interactions with hypertension for WHTR (P < 0.001), waist circumference (P = 0.006) and BMI (P = 0.044) showed that there was an increasing incidence of CVD with increasing adiposity in non-hypertensive men but, in men with treated hypertension, although the overall incidence of CVD was higher, the relationship with adiposity was inverse. In the women, there were no significant linear trends for waist circumference, WHTR or BMI. Quintile estimates were more consistent with J-shaped curves with the lowest risk in the second quintile. Excluding the hypertensive women, increased the significance of these trends. In normotensive women, there was a significant quadratic trend (P = 0.039) for the association between the incidence of CVD and the quintiles of waist circumference, but no associations for WHTR or BMI. For waist circumference there was weak evidence of an interaction with hypertension (P = 0.053).

CONCLUSIONS

For the men, indices involving waist circumference, particularly WHTR, had stronger linear associations with the log odds of CVD development than BMI. The interactions with hypertension were significant for WHTR, waist circumference and also BMI. In women, none of the indices was linearly associated with the log odds of CVD development, but there was a significant J-shaped curve for waist circumference and evidence of an interaction with hypertension. These results suggest that studies in which hypertensives are included, but in which possible hypertension interactions are overlooked, important hypertensive-specific associations between anthropometric indices and CVD development may be masked. Men on anti-hypertensive medication with the lowest central adiposity, experienced higher short-term CVD risk than those with greater central adiposity.