Long-term stable obesity increases risk of hypertension.

OBJECTIVES: Although some prospective cohort studies have shown that baseline BMI is positively associated with a future incident risk for hypertension, these studies do not account for weight changes during the observation period. Therefore, it is not evident whether future incident risk for hypertension in obese, non-hypertensive people increases when their weight remains stable. We examined the association between long-term weight stability and risk for developing hypertension.
METHODS: A total of 5201 Japanese male workers aged 30-59 years underwent health checkups in 2002 and were followed through 2006. To consider transitions in covariates during the follow-up period, we used a time-dependent covariate Cox proportional hazard model to compute the relative risks (RRs) of incident hypertension. Furthermore, as a complementary analysis, we restricted the data to individuals whose BMI remained unchanged (± 5% of baseline BMI) during the follow-up and compared the RRs between BMI categories.
RESULTS: During the follow-up, there were 899 newly diagnosed cases of hypertension among the 5201 men (14,888 person-years). Mean change in BMI during the follow-up period of all subjects was 0.2 ± 1.1 kg/m(2) (range: -6.6 to 6.3 kg/m(2)). The multivariate RRs for hypertension increased as BMI increased when we applied the time-dependent covariate Cox proportional hazard model. The complementary analysis showed that the multivariate RR (confidence interval) within the ≥ 27.0 kg/m(2) BMI category was 1.43 (1.16-1.77) times higher than the reference of 23.0-24.9 kg/m(2), whereas the RR for the <21.0 kg/m(2) BMI category was 0.63 (0.51-0.79) times lower than the reference.
CONCLUSIONS: A higher baseline BMI increases future incident risk for hypertension even when there has been no major weight increase. Weight management should be encouraged for obese, non-hypertensive people to prevent future hypertension.