Incident fracture and osteoporosis risk in middle-aged women with type 1 diabetes: A 15-year longitudinal study

Objectives: To determine the relative risk of incident fracture and osteoporosis diagnoses in middle-aged women with Type 1 diabetes (T1D), compared to age-matched controls, and to examine baseline risk factors for fracture and osteoporosis in this group. Methods: Longitudinal observational study using data from the Australian Longitudinal Study in Women’s Health, of 106 women with self-reported T1D and 11,761 age-matched controls. Women were followed for up to 15 y over 6 questionnaires. The main outcomes of interest were self-reported incident fracture and osteoporosis diagnoses. Women with type 2 diabetes were excluded from the study. Results: No differences between mean age at baseline (47.4±1.5 vs. 47.1±1.5 years, p=0.08) or BMI (25.4 ±5.0 vs. 25.8±5.0 kg/m2, p=0.57) were observed between women with T1D or controls. Mean age at menopause was lower (47.7±3.4 vs. 50.3±3.7 y, p<0.001) in women with T1D. 1180 fractures and 1013 new diagnoses of osteoporosis occurred in the control group, compared to 16 fractures and 18 new diagnoses of osteoporosis in the group with T1D, over 155,328 person-years of follow-up. Incidence rate ratios for fracture and osteoporosis in women with type 1 diabetes vs. controls, were 1.44 (95%CI 0.76 – 2.47, p=0.21) and 2.02 (95%CI 1.17 – 3.24, p=0.001), respectively. The mean time to fracture (7.2±4.3 vs. 9.8±4.3 years, p=0.03) and new osteoporosis diagnoses (6.7±4.6 vs. 8.8±4.0 years, p=0.02) was shorter in women with T1D. Among women with T1D, those with a new diagnosis of osteoporosis had lower BMI (22.9±2.7 vs. 26.0 ±5.2 kg/m2, p=0.04) and underwent menopause earlier (45.8±4.2 vs. 48.1±3.1 years, p=0.04). No differences in characteristics were observed between women with T1D with or without incident fracture. Conclusions: The incidence rate of self-reported osteoporosis is two-fold greater in women with T1D compared to controls. While incident fracture rates were not different, time to fracture was shorter in women with T1D. Women with T1D reach menopause at a younger age than controls, and the perimenopausal period provides an important opportunity for bone health assessment in this cohort.