Abstract
To quantify the risk of hospital admission in relation to fine increments in body mass index (BMI). 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. 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. 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. 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.
Highlights
Obesity rates have doubled or tripled in many countries over the past three decades, and in almost half of all Organization for Economic Co-operation and Development countries 50% or more of the population is overweight or obese.[1]
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
Above normal body mass index (BMI), the relative risk of hospitalisation increases with even small increases in BMI, less so in the elderly
Summary
Obesity rates have doubled or tripled in many countries over the past three decades, and in almost half of all Organization for Economic Co-operation and Development countries 50% or more of the population is overweight or obese.[1] It is known that obesity, and to a lesser extent overweight, increases the risk of mortality 2,3 and many chronic diseases.[4] while pooled analyses have provided reliable evidence of increasing mortality with incremental increases in body mass index (BMI) above the normal range[2,3] there is more limited information on the precise relationship between BMI and other important measures of disease and health service use, such as hospitalisation.[5,6,7,8,9,10,11] while there is considerable evidence supporting the link between obesity and these outcomes ( total hospital use), the evidence on the risk of outcomes in people who are overweight but not obese is less clear.
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