Gender differences in fracture risk and bone mineral density.

We have investigated gender-related differences of bone mineral density and fracture threshold in 136 males (age, 60.7+/-9.3 years) and 337 females (age, 59.7+/-7.8 years) without evidence of secondary osteoporosis. Women and men were examined for total amount of spine fractures and bone mineral density by quantitative computed tomography (QCT) of three non-fractured vertebral bodies L1-L5. Females with lumbar fractures (n=96) when compared with non-fracture women (n=241) were older and had lower bone density at their vertebral sites. Males with vertebral fractures (n=52) were older and had a significantly reduced bone mineral density of the spine when compared with healthy males (n=84). When we compared gender-related vertebral fracture rates, we observed a significantly higher prevalence of vertebral fractures in the male population. After matching males and females for age and bone mineral density to exclude an influence of either variable, we compared the prevalence of vertebral fracture risk in both sexes with logistic regression analysis. Data of estimated fracture risk, differed very significantly for sex and bone density at the vertebral site, indicating that men present fracture at a higher bone density level compared with females; in 10% of study population fractures occurred at a QCT level of 105 mg/cm(3) in women and 120 mg/cm(3) in men. The estimated odds ratio for sex of 3.1 (95% CI) means a three-fold increased risk for vertebral fractures compared to males at a given density level. These results underline that a decreased bone mineral density leads to the occurrence of spine fractures in females and males as well.