Fractures at various skeletal sites are dependent on different risk factors: the results from 10 years of prospective longitudinal observation in postmenopausal women from the RAC-OST-POL Study.

Introduction: The aim of the study was to present data on risk factors for fractures in various parts of the skeleton in a cohort of postmenopausal women during a 10-year prospective observation period. It can be hypothesised that fracture risk factors should be different for spine, hip, and peripheral fractures.

Material and methods: 640 postmenopausal women at mean baseline age was 65.0 ± 6.9 years were enrolled into the study. The cohort was randomly selected from the population of the entire Racibórz district. Data on the incidence of fractures and falls were updated annually during the 10-year follow-up period. Information on clinical risk factors for fractures was collected at baseline.

Results: During the observation period, 190 low-traumatic fractures were recorded in 129 patients. The following number of fractures was observed: hip 15, spine 30, non-hip fractures other than spine 145 (including 81 forearm fractures). The effect of falls was insignificant in the case of spine fractures (chi-square test: 3.64; p = 0.06). For all other skeletal sites, the incidence of fractures was significantly increased by falls, with the greatest effect observed for forearm fractures and non-spine and non-hip fractures (chi-square test for hip, forearm, and all non-spine, non-hip fractures was 6.43, p < 0.05; 42.7, p < 0.0001 and 66.7, p < 0.0001, respectively). To determine the factors having a significant impact on the incidence of fractures during the observation period, logistic regression was used separately in subgroups. The following risk factors were taken into account: age, height, body weight, bone mineral density (BMD) at the femoral neck as expressed by T-score, rheumatoid arthritis, steroid use, falls reported at baseline, and the total number of risk factors. Spine fractures depended only on T-score, odds ratio (OR) = 0.42 (0.23-0.76); hip fractures depended only on age, OR = 1.15 (1.07-1.24); forearm fractures depended only on age T-score, OR = 0.69 (0.51-0.92); and non-hip, non-spine on fall rate, OR = 1.86 (1.20-2.87).

Conclusions: Fractures at various skeletal sites recorded in long-term follow-up in postmenopausal women were dependent on various risk factors. Multivariate analysis identified a single, dominant risk factor for each fracture location analysed.