The prevalence of obesity and hypertension is increasing in Western societies. We examined the effects of initial body mass index ([BMI] weight in kilograms divided by height in meters squared) and change in BMI on change in blood pressure, and we assessed sex differences.
A general population in the municipality of Tromsø, northern Norway, was examined in 1986 and 1987 and again in 1994 and 1995. Altogether, 75% of the individuals, women aged 20 to 56 years and men aged 20 to 61 years, attended the baseline examination. A total of 15,624 individuals (87% of all still living in the municipality) were examined twice.
Mean BMI increased between the examinations, more for the younger than the older examinees, and also more among women than men (P<.001). Adjusted for several covariates, BMI change was associated with systolic and diastolic blood pressure change for both sexes (regression coefficients: 1.43 [95% confidence interval (CI), 1.23-1.64] and 0.90 [95% CI, 0.76-1.04], respectively, for men; and 1.24 [95% CI, 1.09-1.39] and 0.74 [95% CI, 0.63-0.84] for women). Baseline BMI was associated with systolic and diastolic blood pressure change for women only (regression coefficients: 0.38 [95% CI, 0.30-0.47] and 0.17 [95% CI, 0.11-0.23], respectively).
For women, both BMI at baseline and BMI change were independently associated with blood pressure change. For a given increase in BMI, obese women had a greater increase in blood pressure than lean women. This was not the case for men, for whom BMI change was the only significant predictor. Furthermore, a BMI increase for obese women induced a greater systolic blood pressure increase compared with men.