Relationship of height, weight and body mass index to the risk of hip and knee replacements in middle-aged women

Abstract

Objectives . To examine the effect of height, weight and body mass index (BMI) on the risk of hip and knee replacement in middle-aged women. Methods . In a prospective cohort study 490 532 women aged 50–69 yrs who were recruited in the UK in 1996–2001 were followed over 2.9 yrs for incident primary hip and knee replacements. Results . Height, weight and BMI were all associated with the risk of hip and knee replacement. Comparing the tallest group (≥170 cm) with the shortest (2 ) to women with a BMI < 22.5 kg/m ² , the relative risks for hip and knee replacement were 2.47 (95%CI 2.11–2.89) and 10.51 (95%CI 7.85–14.08), respectively. These effects did not vary according to age, education, alcohol and tobacco consumption, or with use of hormonal therapies. Currently, an estimated 27% of hip replacements and 69% of knee replacements in middle-aged women in the UK are attributable to obesity. Conclusion . In middle-aged women, the risk of having a hip or knee replacement increases with both increasing height and increasing BMI. From a clinical perspective, relatively small increases in average BMI among middle-aged women are likely to have a substantial impact on the already increasing rates of joint replacement in the UK.