Prospective cohort study of body mass index and the risk of hospitalisation: findings from 246?361 participants in the 45 and Up Study.

International journal of obesity (2005)

PubMedID: 22986682

Korda RJ, Liu B, Clements MS, Bauman AE, Jorm LR, Bambrick HJ, Banks E. Prospective cohort study of body mass index and the risk of hospitalisation: findings from 246?361 participants in the 45 and Up Study. Int J Obes (Lond). 2012;.
Objective:To quantify the risk of hospital admission in relation to fine increments in body mass index (BMI).Design, setting and participants:Population-based prospective cohort study of 246?361 individuals aged ?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.Main outcomes: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.International Journal of Obesity advance online publication, 18 September 2012; doi:10.1038/ijo.2012.155.