Loss of hip BMD in older men: the osteoporotic fractures in men (MrOS) study.

Previous studies in older men have not evaluated whether loss of BMD or BMC accelerates nonlinearly with age. This study aimed to describe hip bone loss (both in BMC and BMD) in older men and to test whether BMD loss accelerates with age in an exponential manner in a cohort of 4720 community-dwelling men >or=65 yr of age. Men had two to three measures of femoral neck (FN) BMD (by DXA) over an average follow-up of 4.6 yr. Change in BMD during follow-up was estimated from mixed effects regression models; the significance of a quadratic term for age was evaluated. Mean FN BMD loss was 0.013 g/cm(2) (-1.72%) during follow-up. The quadratic term for age was significant, and the model showed that bone loss accelerated with age. Estimated loss of FN BMD over follow-up for men 85 yr of age (0.021 g/cm(2)) was 2.5 times greater than the loss expected for men 65 yr of age (0.008 g/cm(2)); such bone loss in 85-yr-old men may be sufficient to increase the risk of hip fracture by 25% (HR per 0.021 g/cm(2) cross-sectional decrease in FN BMD: 1.25; 95% CI: 1.18-1.31) over 4.6 yr. Men with lower BMD at baseline lost the most BMD over follow-up. Although average bone loss over time is modest in older men, there is considerable variability in rate of loss. Older men and those with lower BMD lose bone more rapidly, offering potential explanation for the increasing risk of fracture with advancing age.