title: Body Mass Index and Incidence of Subarachnoid Hemorrhage in Japanese Community Residents: The Jichi Medical School Cohort Study.
abstract: BACKGROUND
  Whereas high body mass index (BMI) is reportedly a risk factor for cardiovascular events in Western countries, low BMI has been reported as a risk factor for cardiovascular death in Asia, including Japan. Although subarachnoid hemorrhage (SAH) is a highly fatal disease and common cause of disability, few cohort studies have examined the associations between BMI and SAH in Japan. This study investigated the associations between BMI and incidence of SAH using prospective data from Japanese community residents.
  
  
  METHODS
  Data were analyzed from 12,490 participants in the Jichi Medical School Cohort Study. Participants were categorized into 5 BMI groups: ≤18.5, 18.6-21.9, 22.0-24.9, 25.0-29.9, and ≥30.0 kg/m2. Multivariate-adjusted hazard ratios (HR) and 95% confidence intervals (CI) were calculated using Cox proportional hazard model with BMI of 22.0-24.9 kg/m2as the reference category.
  
  
  RESULTS
  During the mean follow-up period of 10.8 years, 55 participants (13 men, 42 women) experienced SAH. BMI ≥30.0 kg/m2was associated with significantly higher risk for SAH (HR, 5.98; 95% CI, 2.25-15.87). BMI ≤18.5 kg/m2showed a nonsignificant tendency toward high risk of SAH (HR, 2.51; 95% CI, .81-7.79).
  
  
  CONCLUSIONS
  High BMI was a significant risk factor for SAH. Lower BMI showed a nonsignificant tendency toward higher risk of SAH. Our results suggest a J-shaped association between BMI and risk of SAH incidence.
authors.affiliation: Graduate School of Saitama Prefectural University, Koshigaya, Saitama, Japan.
authors.forename: Nami
authors.initials: N
authors.lastname: Kawate
authors.affiliation: Graduate School of Saitama Prefectural University, Koshigaya, Saitama, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Kayaba
authors.affiliation: Graduate School of Saitama Prefectural University, Koshigaya, Saitama, Japan. Electronic address: hara-motohiko@spu.ac.jp.
authors.forename: Motohiko
authors.initials: M
authors.lastname: Hara
authors.affiliation: Graduate School of Saitama Prefectural University, Koshigaya, Saitama, Japan.
authors.forename: Toyohiro
authors.initials: T
authors.lastname: Hamaguchi
authors.affiliation: Department of Clinical Laboratory Medicine, Department of Public Health, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kotani
authors.affiliation: Division of Community and Family Medicine, Center for Community Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Shizukiyo
authors.initials: S
authors.lastname: Ishikawa
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D016009:Chi-Square Distribution; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D057187:Independent Living; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology*; D016016:Proportional Hazards Models; D012307:Risk Factors; D012577:Schools, Medical; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis / Q000453:epidemiology*; D013851:Thinness / Q000175:diagnosis / Q000453:epidemiology*
keywords: Body mass index; Japanese population; community-based cohort study; subarachnoid hemorrhage