title: Prospective cohort study of body mass index and the risk of hospitalisation: findings from 246361 participants in the 45 and Up Study.
abstract: OBJECTIVE
  To quantify the risk of hospital admission in relation to fine increments in body mass index (BMI).
  
  
  METHODS
  Population-based prospective cohort study of 246,361 individuals aged greater than or equal to 45 years, from New South Wales, Australia, recruited from 2006-2009. Self-reported data on BMI and potential confounding/mediating factors were linked to hospital admission and death data.
  
  
  RESULTS
  Cox-models were used to estimate the relative risk (RR) of incident all-cause and diagnosis-specific hospital admission (excluding same day) in relation to BMI.
  
  
  RESULTS
  There were 61,583 incident hospitalisations over 479,769 person-years (py) of observation. In men, hospitalisation rates were lowest for BMI 20-<25 kg m(-2) (age-standardised rate: 120/1000 py) and in women for BMI 18.5-<25 kg m(-2) (102/1000 py); above these levels, rates increased steadily with increasing BMI; rates were 203 and 183/1000 py, for men and women with BMI 35-50 kg m(-2), respectively. This pattern was observed regardless of baseline health status, smoking status and physical activity levels. After adjustment, the RRs (95% confidence interval) per 1 kg m(-2) increase in BMI from ≥ 20 kg m(-2) were 1.04(1.03-1.04) for men and 1.04(1.04-1.05) for women aged 45-64; corresponding RRs for ages 65-79 were 1.03(1.02-1.03) and 1.03(1.03-1.04); and for ages ≥ 80 years, 1.01(1.00-1.01) and 1.01(1.01-1.02). Hospitalisation risks were elevated for a large range of diagnoses, including a number of circulatory, digestive, musculoskeletal and respiratory diseases, while being protective for just two-fracture and hernia.
  
  
  CONCLUSIONS
  Above normal BMI, the RR of hospitalisation increases with even small increases in BMI, less so in the elderly. Even a small downward shift in BMI, among those who are overweight not just those who are obese, could result in a substantial reduction in the risk of hospitalisation.
authors.affiliation: National Centre for Epidemiology and Population Health, The Australian National University, Canberra, Australian Capital Territory, Australia; Australian Centre for Economic Research on Health, The Australian National University, Canberra, Australian Capital Territory, Australia.
authors.forename: R J
authors.initials: RJ
authors.lastname: Korda
authors.forename: B
authors.initials: B
authors.lastname: Liu
authors.forename: M S
authors.initials: MS
authors.lastname: Clements
authors.forename: A E
authors.initials: AE
authors.lastname: Bauman
authors.forename: L R
authors.initials: LR
authors.lastname: Jorm
authors.forename: H J
authors.initials: HJ
authors.lastname: Bambrick
authors.forename: E
authors.initials: E
authors.lastname: Banks
mesh_terms: D000368:Aged; D001249:Asthma / Q000453:epidemiology* / Q000503:physiopathology; D001315:Australia / Q000453:epidemiology; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D048909:Diabetes Complications / Q000453:epidemiology* / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D005767:Gastrointestinal Diseases / Q000453:epidemiology* / Q000503:physiopathology; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009517:New South Wales / Q000453:epidemiology; D009765:Obesity / Q000150:complications* / Q000453:epidemiology / Q000503:physiopathology; D010003:Osteoarthritis / Q000453:epidemiology* / Q000503:physiopathology; D011159:Population Surveillance; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology / Q000503:physiopathology