New research suggests that individuals with a high body mass index (BMI) and high systolic blood pressure are at an increased risk for stroke mortality.
This large, population-based study suggests that BMI is predictive of stroke mortality in individuals who are overweight or obese.
The prospective study of mortality included 211,946 Chinese men 40 to 79 years old from 145 surveillance centers across China without known cardiovascular disease at study enrollment.
After 10-years of follow-up, investigators found that although there was a strong positive relationship between BMI and systolic blood pressure and between systolic blood pressure and stroke mortality, the association between BMI and stroke mortality was not linear.
"The results of this study could suggest that, below the range of BMI 25 kg/m2, the adverse effects of high BMI on blood pressure may be counterbalanced by an inverse association between BMI and some other stroke risk factors," the study authors write.
According to the investigators, prospective cohort studies consistently report a positive link between increasing BMI and ischemic heart disease.
For the study, all men aged 40 years or older from 145 disease surveillance points situated in 45 areas (urban and rural) across China were recruited. These surveillance points were established by the Chinese government in the 1980s and provide a nationally representative sample of mortality statistics for the entire country.
At baseline, all study participants were interviewed with use of a standardized questionnaire about smoking and other exposures. Height, weight, blood pressure, and peak expiratory flow rate were measured.
After the initial survey, study participants were monitored passively with use of death registries and active, annual confirmation by local residential committees. The average systolic blood pressure of subjects was 124 mm Hg and the average BMI was 21.7 kg/m2, much lower than those seen in typical Western populations.
During the study period, there were 27,758 deaths. Of these deaths, 5766 (20%) individuals had died of a stroke. Of these stroke deaths, 570 were of unknown cause. Of the remainder, 3609 (69%) died of a hemorrhagic stroke, 1231 (24%) of an ischemic stroke, and 356 of a subarachnoid hemorrhage.
The study authors report that for every 3-mm Hg higher baseline systolic blood pressure, there was a 5.6% higher stroke mortality. However, despite the fact that men with a higher BMI had a higher systolic blood pressure, stroke mortality increased only in those whose BMI was higher than 25 kg/m2.
- Previous research has suggested a positive relationship between BMI and a higher risk for coronary heart disease, and the effects of higher BMI on blood pressure, serum lipid levels, and blood glucose tolerance levels seem to be the causative factors in promoting higher coronary risk.
- The current study finds that a BMI of more than 25 kg/m2 increased the risk for stroke mortality among men.
Stroke. Published online January 31, 2008.