Impact of obesity on incident hypertension independent of weight gain among nonhypertensive Japanese: the Ibaraki Prefectural Health Study (IPHS).

OBJECTIVE

The aim of this study was to examine the association between BMI and risk of incident hypertension among Japanese men and women who are middle-aged and older.

DESIGN

Prospective, population-based cohort study.

PATIENTS

A total of 68 205 nonhypertensive adults (18 336 men and 49 869 women) aged 40-79 years who completed health check-ups in the Ibaraki prefecture, Japan, in 1993 were followed up through 2006. To exclude the impact of BMI change during the follow-up period, a time-dependent covariate Cox proportional hazards model was used to compute the hazard ratios of incident hypertension according to BMI categories. Incident hypertension was defined as a SBP of at least 140 mmHg, a diastolic BP of at least 90 mmHg, and/or hypertensive medication use.

RESULTS

A total of 30 982 adults (45.4%) developed hypertension (9331 men and 21 651 women) during a mean of 3.9 years of follow-up. Compared with a BMI of less than 19.0, time-dependent covariates adjusted hazard ratios [95% confidence interval (CI)] for hypertension among participants with a BMI of at least 25.0 were 1.42 (1.17-1.73) for men aged 40-59 years, 1.34 (1.19-1.51) for men aged 60-79 years, 1.47 (1.33-1.62) for women aged 40-59 years, and 1.29 (1.18-1.41) for women aged 60-79 years.

CONCLUSION

The baseline BMI is associated with future risk for incident hypertension even after accounting for weight change during the follow-up period. Weight loss may be recommended to nonhypertensive obese adults to prevent the development of hypertension.