Duration of obesity and incident hypertension in adults from the Framingham Heart Study
The association between obesity and hypertension is well established. However, obesity assessment is often done at one point in time, and the potential cumulative effect of excess adiposity over time on risk of hypertension is uncertain. We recently demonstrated that obesity duration is positively associated with risk of diabetes and mortality, independent of attained BMI. This study aimed to examine the relationship between duration of obesity and incident hypertension using the Framingham Heart Study.
METHODS:
2,953 participants aged 28-62 years without hypertension at baseline (1948–1950) were included. Blood pressure, height and weight were measured biennially for approximately 60 years. Duration of obesity was calculated for individuals with ≥2 consecutive occurrences of obesity to avoid potential misclassification. Missing data were imputed. Analyses were done using Cox proportional hazards regression with age as the time scale. Participants were censored at the first occurrence of hypertension, death or end of follow-up, whichever came first. A test for interaction between sex and duration of obesity was performed. Sensitivity analyses were done: (i) excluding participants with missing values; (ii) stratified by baseline obesity status; and (iii) using single examinations with obesity to calculate duration of obesity.
RESULTS:
80% of participants developed hypertension (median follow-up 15.9 years). Duration of obesity was associated with incident hypertension in men and women (hazard ratio (HR) 1.03 (95% CI 1.01, 1.05) and 1.04 (1.02, 1.05), respectively). Significance was lost when BMI was added to the model. Results remained virtually unchanged in all sensitivity analyses. No interaction was observed between sex and duration.
CONCLUSIONS:
There was no relationship between duration of obesity and incident hypertension independent of BMI. This suggests that the mechanism by which excess adiposity may increase blood pressure is more immediate and long-term exposure to obesity does not increase the risk of developing hypertension beyond the level of BMI attained.