An association between respiratory function and hip bone mineral density in older men: a cross-sectional study

The association between respiratory function and bone mineral density (BMD) among women living in the community has been reported previously. We examined the association between forced expiratory volume in 1 s (FEV₁) and BMD measured at hip using dual-energy X-ray absorptiometry in a group of 947 men (aged 65 to 76 years) recruited from general practice age-sex registers in Cambridge between 1991 and 1995. A positive and significant correlation was seen between FEV₁ and BMD measured at total hip, femoral neck, and trochanter. A unit change (1 l) in FEV₁ was associated with a change of BMD by 0.019, 0.017, and 0.026 g/cm² in the total hip, femoral neck, and tochanteric region, respectively. These associations were independent of possible confounding factors such as age, height, weight, smoking habit, major disease prevalence, and medications, which might affect bone metabolism. In categorical analyses, the highest BMD was seen in the highest FEV₁ quartile, while the lowest BMD was seen in the lowest FEV₁ quartile. This pattern was seen in all three skeletal sites and was independent of covariates listed above. Compared with the bottom FEV₁ quartile, mean hip BMDs in the top quartile were 2–3.5% higher. The exact mechanism of this association is not clear to us. One plausible explanation is that respiratory function and bone health both reflect common but as yet unknown determinants.