Association between a family history of fractures and bone mineral density in early postmenopausal women.

The aim of this analysis was to measure the strength of the association between a family history of fractures and bone mineral density (BMD), and to determine what definition of family fracture history best predicts BMD. Five hundred and eighty postmenopausal women aged 45-59 at recruitment completed a risk factor questionnaire. Women were asked to recall details of fractures sustained by any female relative. BMD measurements taken at five sites were used. The data were analysed using linear regression, adjusting for age. Two hundred and ninety-seven (52.8%) women reported a family history of fractures, and they had a significantly lower BMD at two of the sites measured (p < 0.05). The associations with BMD were most significant when only counting fractures that occurred in the subject's mother or a sister as a result of low trauma, with no restrictions made on age at the time of fracture and site of fracture (p < 0.01 at three sites; 0.01 < p < 0.05 at two sites). Women with a family history according to this definition had a 4.6% reduction in BMD at the femoral neck. When T scores were used to categorize women as either osteopenic/osteoporotic (T < -1) or normal at the femoral neck, the sensitivity of using this definition was 39% and the specificity was 74%. The small group of women that reported a low-trauma hip fracture in a mother or sister (n = 23) had a mean femoral neck BMD which was 8.9% lower than that of the remainder of the sample, although this difference was less statistically significant than when low trauma fractures at any site were counted. Of these 23 women, 70% were osteopenic or osteoporotic, compared with 57% of those reporting a low-trauma fracture at any site and 47% of the sample as a whole. The sensitivity of this definition, however, was low (6%). From these analyses it can be concluded that the definition of family fracture history that best predicts BMD in postmenopausal women is a fracture at any age in a mother or sister resulting from low trauma, although the sensitivity and specificity of using a family history of fractures by itself to screen for low BMD were poor.