Prevalence and trends in low femur bone density among older US adults: NHANES 2005-2006 compared with NHANES III.

Hip fracture incidence appears to be declining in the United States, but changes in bone mineral density (BMD) of the population have not been evaluated. We used femur BMD data from the National Health and Nutrition Examination Survey (NHANES) 2005-2006 to estimate the prevalence of low femoral BMD in adults age 50 years and older and compared it with estimates from NHANES III (1988-1994). Dual-energy X-ray absorptiometry systems (pencil-beam geometry in NHANES III, fan-beam geometry in NHANES 2005-2006) were used to measure femur BMD, and World Health Organization (WHO) definitions of low BMD were used to categorize skeletal status. In 2005-2006, 49% of older US women had osteopenia and 10% had osteoporosis at the femur neck. In men, 30% had femur neck osteopenia and 2% had femur neck osteoporosis. An estimated 5.3 million older men and women had osteoporosis at the femur neck, and 34.5 million more had osteopenia in 2005-2006. When compared with NHANES III, the age-adjusted prevalence of femur neck osteoporosis in NHANES 2005-2006 was lower in men (by 3 percentage units) and women (by 7 percentage units) overall and among non-Hispanic whites. Changes in body mass index or osteoporosis medication use between surveys did not fully explain the decline in osteoporosis. Owing to the increase in the number of older adults in the US population, however, more older adults had low femur neck BMD (osteoporosis + osteopenia) in 2005-2006 than in 1988-1994. Thus, despite the decline in prevalence, the estimated number of affected older adults in 2005-2006 remained high. 2010 American Society for Bone and Mineral Research