The baseline characteristics of the 13,563 normotensive participants are shown according to BMI quintiles in . Men with higher BMI reported higher systolic and diastolic BP at baseline. As expected, men with higher BMI were more likely to have diabetes and high cholesterol. They were also more likely to smoke, consumed less alcohol, and were less physically active.
Baseline Characteristics of 13,563 Participants According to Baseline Body Mass Index (BMI, in kg/m2)
Among 13,563 men, 4,920 cases of incident hypertension developed during a median follow-up of 14.5 years (maximum follow-up, 20.5 years). In age- and multivariable-adjusted analyses, higher baseline BMI was significantly associated with increased risk of incident hypertension (). The age-adjusted estimated risk of hypertension generally increased across BMI quintiles relative to the referent group (BMI <22.4 kg/m2), even within the range of “normal” BMI. Higher BMI remained associated with risk of hypertension after adjustment for the potential confounders (age, cigarette smoking status, alcohol consumption, exercise, and parental history of premature myocardial infarction). The multivariable-adjusted RR of hypertension for men in the highest BMI quintile (>26.4 kg/m2) was 1.85 (95% CI, 1.69–2.03; P for trend, <0.001), as compared to those in the lowest BMI quintile (<22.4 kg/m2).
Relative Risks of Developing Hypertension, According to Baseline Body Mass Index
Further adjustment for the potential mediators (diabetes and high cholesterol) did not materially alter the results (Model 2, ). Additionally adjusting for baseline systolic and diastolic BP only partly attenuated the effect estimates of the association between BMI and risk of hypertension. Compared to men in the lowest BMI quintile, the RR of hypertension for men in the highest quintile was 1.47 (95% CI, 1.34–1.62; P for trend, <0.001).
Examining baseline BMI as a continuous term, each 1-unit increase in BMI was associated in multivariable models with an 8% (95% CI, 7–9%) increase in the risk of incident hypertension (Model 2). We found similar associations evaluating BMI according to WHO categories and in deciles. The multivariable-adjusted RRs of hypertension were 1.42 (95% CI, 1.33–1.50) for overweight men and 1.95 (95% CI, 1.68–2.25) for obese men (P for trend, <0.001), as compared to men of normal BMIs. Men in the highest decile of baseline BMI (>27.8 kg/m2) had a multivariable-adjusted RR of hypertension of 2.33 (95% CI, 2.04–2.66; P for trend, <0.001), as compared to men with BMI <21.6 kg/m2 ().
Multivariable-adjusted relative risk of developing hypertension, according to baseline body mass index decile (BMI kg/m2)
We found similar associations between baseline BMI and risk of hypertension when limiting analyses to the 7,016 men without a history of cigarette smoking at baseline. Further excluding men who developed hypertension or who were censored during the first 2 years of follow-up only slightly attenuated the results ().
In additional analyses, we found similar associations between baseline BMI and risk of hypertension after excluding those who were obese, had high cholesterol or missing cholesterol information, or who reported diabetes at baseline (n=3,361). Adjusting for potential confounders, men in the highest BMI quintile (>26.4 kg/m2) had a RR of incident hypertension of 1.75 (95% CI, 1.57–1.95; P for trend, <0.001), as compared to men in the lowest quintile (<22.4 kg/m2).
Regardless of smoking status, the risk of developing hypertension significantly increased across BMI quintiles relative to the lowest quintile in both age- and multivariable-adjusted models (; P for trend, <0.001). Although the magnitude of the association between BMI and risk of hypertension was stronger for past smokers, we did not detect effect modification by baseline smoking status (LRT, P interaction = 0.60).
Relative Risks of Developing Hypertension, According to Baseline Body Mass Index and Cigarette Smoking Status
We also performed analyses on BMI and hypertension stratified by either baseline systolic or diastolic BP. Again, for each baseline BP category, the risk of developing hypertension significantly increased across BMI quintiles in both age- and multivariable-adjusted models (P for trend, <0.001). For systolic BP, the multivariable-adjusted RR (95% CI) comparing the highest and lowest BMI quintiles was 1.82 (1.45–2.28) among those with systolic BP <120 mmHg, versus 1.64 (1.48–1.82) among those with systolic BP 120–139 mmHg (LRT, P interaction = 0.19). By contrast, the association between BMI and risk of hypertension was stronger for men with diastolic BP <80 mmHg (RR [95% CI], 1.84 [1.56–2.16]), as compared to men with diastolic BP 80–89 mmHg at baseline (RR [95% CI], 1.58 [1.40–1.77]); LRT, P interaction = 0.02.
The risk of developing hypertension was similar between men <60 years of age at baseline and men >60 years in models considering the joint effects of age and BMI (). In models including joint effects of baseline BMI quintiles and BP, the RR of developing hypertension was consistently highest among men with higher BP at baseline, across all BMI quintiles ().
Multivariable-adjusted relative risk for developing hypertension, according to BMI quintile (kg/m2), age, and blood pressure at baseline
In secondary analyses, we examined the associations between weight change over 8 years and subsequent risk of developing hypertension. Overall, 8-year mean change in BMI (SD) was +2.0 (5.9)%, varying from +0.35 (8.4)% among those who were obese at baseline to +2.2 (5.6)% among those with BMI <25.0 kg/m2 at baseline (P<0.001). Adjusting for the potential confounders, men whose BMI increased by more than 5% had a significantly increased risk of developing hypertension after 8 years. Men whose BMI increased by >5 – 10% had a RR of 1.21 (95% CI, 1.09–1.35), and men whose BMI increased by >10% had a RR of 1.72 (95% CI, 1.48–1.99), as compared to men whose weight remained stable (BMI within 5% of baseline). Men whose BMI decreased by more than 5% were at similar risk for developing hypertension as compared to those with stable BMI (RR, 0.91; 95% CI, 0.77–1.08). Again, further adjustment for the potential mediators did not alter the associations. Across all baseline BMI levels, 8-year weight gains of >5% were associated with a significantly increased risk of developing subsequent hypertension. In stratified analyses adjusting for both potential confounders and mediators, weight gain was most strongly associated with increased hypertension risk among men who were obese at baseline (RR, 2.49; 95% CI, 1.05–5.91, for BMI increases >10% vs. stable weight), as compared to those who were overweight (RR, 1.77; 95% CI, 1.41–2.22) or normal weight (RR, 1.58; 95% CI, 1.30–1.93) at baseline.