Body Mass Index and Risk of Stroke Mortality among a Random Sample of Japanese Adults: 19-Year Follow-Up of NIPPON DATA80

Abstract

Background: The relationship between body mass index (BMI) and stroke mortality remains unclear. The aim of the present study was to elucidate the relationship between BMI and stroke death in a representative cohort of Japanese men and women. Methods: We analyzed a database of 9,526 men and women aged 30 years and older who were randomly selected throughout Japan in 1980. These individuals had no history of stroke and were followed for 19 years. Hazard ratios (HR) and their 95% confidence intervals (CI) of deaths due to total stroke, cerebral infarction, and intracerebral hemorrhage were examined using Cox’s proportional hazards regression models of BMI levels. Results: A U-shaped association between BMI and cerebral infarction mortality was observed. Participants with the highest BMI category (BMI ≧ 30.0) showed a significantly highest HR for cerebral infarction (HR 2.46, 95% CI 1.01–5.99). The excess risk at the lower extreme of the BMI was confined to men. These associations did not change after excluding deaths occurring in the first 2 years of follow-up. Conclusions: In the Japanese general population, a U-shaped association between BMI and cerebral infarction mortality was found and the excess risk at the lower extreme of the BMI was confined to men.

Body mass index and stroke incidence in a Japanese community: the Hisayama study

“…9,12,13,16,19,21,22 In the present study, we did not find a clear association between BMI levels and hemorrhagic stroke in men or women. The lack of a clear consensus on this association may be partly due to the low number of cases of hemorrhagic stroke in most of the studies, including our present work, or differences in ethnicities, study populations or study methods.…”

“…Several cohort studies have also examined the effects of BMI on the risk of ischemic stroke in women, 9,[13][14][15]21,22 but the findings were inconsistent, with some studies showing a positive association, 9,13,14 and others showing no association 15,21 like our study. Further studies will be needed to clarify the true association between BMI and stroke in women.…”

“…On the other hand, other studies have found no association, [15][16][17][18] an inverse or a U-shaped association. [19][20][21][22] One possible explanation for this difference in findings may be that stroke was not evaluated by its subtype in all these studies, as the effect of obesity is different among stroke subtypes. Another explanation may be that most of these studies used mortality data as an endpoint.…”

“…Some cohort studies have found a positive association between BMI and the risk of stroke, [8][9][10][11][12][13][14] whereas others have shown no apparent association [15][16][17][18] or have even reported an inverse or a U-shaped association. [19][20][21][22] In Japan, no prospective study has provided incidence data on this issue nor observed a positive association between BMI and the risk of stroke until now. 21,22 Based on its pathogenesis, stroke is divided into several clinical subtypes, and the effects of BMI on stroke are considered to be different among these subtypes.…”

“…[19][20][21][22] In Japan, no prospective study has provided incidence data on this issue nor observed a positive association between BMI and the risk of stroke until now. 21,22 Based on its pathogenesis, stroke is divided into several clinical subtypes, and the effects of BMI on stroke are considered to be different among these subtypes. 8,19 In addition, obesity is an important risk factor for hypertension, diabetes mellitus and dyslipidemia, which are known as major risk factors for stroke, 23,24 and therefore, whether obesity itself independently increases the risk of stroke remains controversial.…”