The prevalence of osteoporosis in an older population with very high body mass index - evidence for an association

BACKGROUND: Studies have demonstrated the beneficial effect of normal and high body mass index (BMI) upon risk of osteoporosis (OP). No study has investigated the prevalence of OP in an older population with a very high BMI (higher than 40 kg/m(2) ).

METHODS: Data of patients aged over 50 years that attended for a dual energy X-ray absorptiometry scan at a UK district general hospital were collated. The population was divided according to BMI increments of 5 kg/m(2) . The prevalence of OP for each BMI category was ascertained. Logistic regression analysis was used to investigate for significant associations between BMI and OP prevalence, adjusted for age, sex and number of OP risk factors.

RESULTS: Data of 10,796 study subjects were collated. Mean age was 67.34 years. Decreasing prevalence of OP was associated with increasing BMI up to 40 kg/m(2) , above which increasing BMI was associated with increasing prevalence of OP.

CONCLUSIONS: The protective effect of increasing BMI exists up to 40 kg/m(2) . A BMI higher than 40 kg/m(2) is associated with increased prevalence of OP. This finding may be attributable to reduced level of bone weight bearing in individuals with a very high BMI.