Original Article

Osteoporosis International

, Volume 16, Issue 11, pp 1330-1338

First online:

Body mass index as a predictor of fracture risk: A meta-analysis

  • C. De LaetAffiliated withScientific Institute of Public Health
  • , J. A. KanisAffiliated withWHO Collaborating Centre for Metabolic Bone Diseases, University of Sheffield Medical School Email author 
  • , A. OdénAffiliated withConsulting Statistician
  • , H. JohansonAffiliated withConsulting Statistician
  • , O. JohnellAffiliated withDepartment of Orthopaedics, Malmö General Hospital
  • , P. DelmasAffiliated withINSERM Unité 149
  • , J. A. EismanAffiliated withBone and Mineral Research Program, Garvan Institute of Medical Research, St Vincent’s Hospital and University of New South Wales
  • , H. KrogerAffiliated withDepartment of Surgery, Bone and Cartilage Research Unit, Kuopio University Hospital
  • , S. FujiwaraAffiliated withDepartment of Clinical Studies, Radiation Effects Research Foundation
    • , P. GarneroAffiliated withINSERM Unité 403
    • , E. V. McCloskeyAffiliated withWHO Collaborating Centre for Metabolic Bone Diseases, University of Sheffield Medical School
    • , D. MellstromAffiliated withDepartment of Geriatric Medicine, Goteborg University
    • , L. J. Melton3rdAffiliated withDivision of Epidemiology, Mayo Clinic
    • , P. J. MeunierAffiliated withINSERM Unit 403, Faculty R Laennec
    • , H. A. P. Pols
    • , J. ReeveAffiliated withStrangeway’s Research Laboratory
    • , A. SilmanAffiliated withARC Epidemiology Unit, University of Manchester
    • , A. TenenhouseAffiliated withDivision of Bone Metabolism, The Montreal General Hospital

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Low body mass index (BMI) is a well-documented risk factor for future fracture. The aim of this study was to quantify this effect and to explore the association of BMI with fracture risk in relation to age, gender and bone mineral density (BMD) from an international perspective using worldwide data. We studied individual participant data from almost 60,000 men and women from 12 prospective population-based cohorts comprising Rotterdam, EVOS/EPOS, CaMos, Rochester, Sheffield, Dubbo, EPIDOS, OFELY, Kuopio, Hiroshima, and two cohorts from Gothenburg, with a total follow-up of over 250,000 person years. The effects of BMI, BMD, age and gender on the risk of any fracture, any osteoporotic fracture, and hip fracture alone was examined using a Poisson regression model in each cohort separately. The results of the different studies were then merged. Without information on BMD, the age-adjusted risk for any type of fracture increased significantly with lower BMI. Overall, the risk ratio (RR) per unit higher BMI was 0.98 (95% confidence interval [CI], 0.97–0.99) for any fracture, 0.97 (95% CI, 0.96–0.98) for osteoporotic fracture and 0.93 (95% CI, 0.91–0.94) for hip fracture (all p <0.001). The RR per unit change in BMI was very similar in men and women ( p >0.30). After adjusting for BMD, these RR became 1 for any fracture or osteoporotic fracture and 0.98 for hip fracture (significant in women). The gradient of fracture risk without adjustment for BMD was not linearly distributed across values for BMI. Instead, the contribution to fracture risk was much more marked at low values of BMI than at values above the median. This nonlinear relation of risk with BMI was most evident for hip fracture risk. When compared with a BMI of 25 kg/m2, a BMI of 20 kg/m2 was associated with a nearly twofold increase in risk ratio (RR=1.95; 95% CI, 1.71–2.22) for hip fracture. In contrast, a BMI of 30 kg/m2, when compared with a BMI of 25 kg/m2, was associated with only a 17% reduction in hip fracture risk (RR=0.83; 95% CI, 0.69–0.99). We conclude that low BMI confers a risk of substantial importance for all fractures that is largely independent of age and sex, but dependent on BMD. The significance of BMI as a risk factor varies according to the level of BMI. Its validation on an international basis permits the use of this risk factor in case-finding strategies.


BMI Fractures Meta-analysis Osteoporosis Prospective studies Risk