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Title: Different effects of age, adiposity and physical activity on the risk of ankle, wrist and hip fractures in postmenopausal women

Authors: M.E.G. Armstrong, B.J. Cairns, E. Banks, J. Green, G.K. Reeves and V. Beral, for the Million Women Study Collaborators

Reference: Bone 50(6): 1394-1400.

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While increasing age, decreasing body mass index (BMI), and physical inactivity are known to increase hip fracture risk, whether these factors have similar effects on other common fractures is not well established. We used prospectively-collected data from a large cohort to examine the role of these factors on the risk of incident ankle, wrist and hip fractures in postmenopausal women. 1,155,304 postmenopausal participants in the Million Women Study with a mean age of 56.0 (SD 4.8) years, provided information about lifestyle, anthropometric, and reproductive factors at recruitment in 19962001. All participants were linked to National Health Service cause-specific hospital records for day-case or overnight admissions. During follow-up for an average of 8.3 years per woman, 6807 women had an incident ankle fracture, 9733 an incident wrist fracture, and 5267 an incident hip fracture. Adjusted absolute and relative risks (RRs) for incident ankle, wrist, and hip fractures were calculated using Cox regression models. Age-specific rates for wrist and hip fractures increased sharply with age, whereas rates for ankle fracture did not. Cumulative absolute risks from ages 50 to 84 years per 100 women were 2.5 (95% CI 2.22.8) for ankle fracture, 5.0 (95%CI 4.45.5) for wrist fracture, and 6.2 (95% CI 5.57.0) for hip fracture. Compared with lean women (BMI < 20 kg/m2), obese women (BMI ≥ 30 kg/m2) had a three-fold increased risk of ankle fracture (RR = 3.07; 95% CI 2.533.74), but a substantially reduced risk of wrist fracture and especially of hip fracture (RR = 0.57; 0.510.64 and 0.23; 0.210.27, respectively). Physical activity was associated with a reduced risk of hip fracture but was not associated with ankle or wrist fracture risk. Ankle, wrist and hip fractures are extremely common in postmenopausal women, but the associations with age, adiposity, and physical activity differ substantially between the three fracture sites.

Keywords. hip fracture, wrist fracture, ankle fracture, physical activity, BMI, postmenopausal women

Acknowledgement. We thank the women who participated in the Million Women Study, the NHS Breast Screening Centre collaborators, and the steering committee of the Million Women Study. We also thank the Information and Statistics Division in Scotland and the Information Centre for Health and Social Care and Northgate Solutions in England for the hospital admission data.

© 2002-2017 Benjamin J. Cairns: e-mail ; ph +44 1865 289673 ;
Cancer Epidemiology Unit, University of Oxford, Richard Doll Building, Roosevelt Drive, Oxford OX3 7LF, U.K.