Insulin Resistance Syndrome and Echocardiographic Left Ventricular Mass in African-Americans
The insulin resistance syndrome (IRS) has been associated with cardiovascular disease (CVD), but few studies have examined its relationship with subclinical measures such as echocardiographic left ventricular (LV) mass. This relationship is likely to be of particular importance in African-Americans where both IRS and elevated LV mass are common. Complete information was available for 1633 African-American women and men aged 49-73 who were enrolled in the Atherosclerosis Risk in Communities (ARIC) Study when M-mode echocardiography was performed at one of the four ARIC sites in Jackson, Mississippi (1993-1996). LV mass was calculated according to American Society of Echocardiography methods using the cube formula and was indexed by height. Participants were categorized by the number (0, 1, 2, or 3) of IRS characteristics (hypertension, dyslipidemia (low HDL cholesterol or high triglyceride), and glucose intolerance (diabetes or fasting glucose values ≥110 mg/dl)). Age-adjusted mean LV mass/height (g/m) increased progressively with increasing number of IRS disorders in both women and men (128.9, 148.6, 161.0, 171.6 and 135.9, 157.4, 170.6, 171.6 respectively, p<0.001, tests for trend). Associations were slightly stronger in women than in men and were similar when participants were stratified by age, BMI and waist circumference. These associations were not altered by adjustment for smoking and alcohol intake, and were only slightly attenuated with adjustment for BMI and waist circumference. Analyses focusing on the components of LV mass revealed that posterior wall and interventricular septal thickness, but not LV chamber size, were significantly associated with the number of IRS disorders. In this large population-based study of middle-aged African-American women and men the degree of IRS clustering was strongly and independently related to LV mass and these associations are consistent with a possible influence of insulin resistance on myocardial thickening rather than chamber size.