Functional Impairments Mediate Association Between Clinical Fracture Risk and Type 2 Diabetes Mellitus in Older Women.

OBJECTIVES: To examine the effect of functional impairments in older women with diabetes mellitus (DM) on incident clinical fractures.

DESIGN: Secondary analysis of two large prospective cohort studies.

SETTING: North Carolina Established Populations for Epidemiologic Studies of the Elderly (EPESE) and Women's Health Initiative (WHI) clinical trials.

PARTICIPANTS: EPESE included 2,704 community-dwelling women aged 65 and older; WHI clinical trials included 68,125 postmenopausal women.

MEASUREMENTS: Women with DM at baseline were compared with women without in successive Cox proportional hazards models. Functional limitations were determined according to self-reported difficulties with activities of daily living (ADLs) and physical activities.

RESULTS: The risk of any clinical fracture during the study period was greater in women with DM, after controlling for age, race and ethnicity, and body mass index, in the EPESE (hazard ratio (HR) = 1.36, 95% confidence interval (CI) = 1.08-1.72) and WHI (HR = 1.29, 95% CI = 1.19-1.39) cohorts. After inclusion of functional limitations, the greater risk of fracture associated with DM decreased in the EPESE (HR = 1.25, 95% CI = 0.98-1.59) and WHI (HR = 1.21, 95% CI = 1.12-1.31) cohorts. In participants with DM, difficulties with moderate physical activities, such as bending or stooping, walking several blocks, and heavy housework, were significantly associated with incident fracture (P < .05).

CONCLUSION: Older women with DM are at greater risk of clinical fractures than those without, independent of bone mineral density. Greater functional impairment in moderate physical activities mediates this greater fracture risk in part, although there remains an unexplained residual DM-associated risk for fracture.