title: Association between body mass index and cause-specific mortality as well as hospitalization in frail Chinese older adults.
abstract: OBJECTIVE
  A U-shaped relationship between body mass index (BMI) and all-cause mortality has been reported, but there are few studies examining the association between BMI and cause-specific mortality and hospitalization. We carried out a longitudinal study to examine these associations in Chinese older adults with multiple comorbidities, which could provide a reference for the recommended BMI in this population.
  
  
  METHODS
  From 2004 to 2013, a retrospective cohort of Chinese older adults was selected from a geriatric day hospital in Hong Kong. They were divided into groups according to their BMI: BMI <16; BMI 16-18; BMI 18.1-20; BMI 20.1-22; BMI 22.1-24; BMI 24.1-26; BMI 26.1-28; BMI 28.1-30 and BMI >30. Other assessments included medical, functional, cognitive, social and nutritional assessment.
  
  
  RESULTS
  A total of 1747 older adults (mean age 80.8 ± 7.1 years, 44.1% male, 46.1% living in nursing homes, Charlson Comorbidity Index 2.0 ± 1.6) with a median follow up of 3.5 years were included. Older adults with BMI 24-28 had the lowest all-cause, infection-related and cardiovascular mortality (P < 0.001). Multivariate analysis showed that there was an inverted J-shaped association between BMI and hazard ratio for all-cause and infection-related mortality in both nursing home and community-dwelling older adults. The rate of all-cause hospitalization was lower in older adults with BMI 22-28 (P = 0.002). Multivariate analysis showed that there was an inverted J-shaped association between the odds ratio of recurrent hospitalization and BMI.
  
  
  CONCLUSIONS
  Chinese older adults with BMI 24-28 had lower all-cause mortality, infection-related mortality, cardiovascular-related mortality and all-cause hospitalization. This study provides a reference for the recommended BMI in this population.
authors.affiliation: Department of Medicine and Geriatrics, Fung Yiu King Hospital, Hong Kong; Division of Geriatric Medicine, Department of Medicine, Queen Mary Hospital, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong.
authors.forename: Tuen-Ching
authors.initials: TC
authors.lastname: Chan
authors.forename: James Ka Hay
authors.initials: JK
authors.lastname: Luk
authors.forename: Leung-Wing
authors.initials: LW
authors.lastname: Chu
authors.forename: Felix Hon Wai
authors.initials: FH
authors.lastname: Chan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D002423:Cause of Death / Q000639:trends; D005260:Female; D005500:Follow-Up Studies; D016330:Frail Elderly / Q000706:statistics & numerical data*; D006304:Health Status; D006723:Hong Kong / Q000453:epidemiology; D006760:Hospitalization / Q000639:trends*; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends
keywords: Chinese older adults; body mass index; hospitalization; mortality; obesity; overweight