Prediabetes and insulin resistance are associated with lower trabecular bone score (TBS): cross-sectional results from the Study of Women’s Health Across the Nation TBS Study

SUMMARY: In pre- and early perimenopausal women, prediabetes (with blood glucose ≥ 110 mg/dL) and greater insulin resistance are associated with worse trabecular bone quality (as assessed by trabecular bone score). PURPOSE: Diabetes mellitus (DM) is associated with lower trabecular bone score (TBS) and fracture; less certain is whether the precursor states of prediabetes and increased insulin resistance are also related to adverse bone outcomes. We examined, in women who do not have DM, the associations of glycemic status (prediabetes vs. normal) and insulin resistance with TBS. METHODS: This was a cross-sectional analysis of baseline data collected from 42- to 52-year-old, pre- and perimenopausal participants in the Study of Women’s Health Across the Nation (SWAN) TBS Study. Women with prediabetes were categorized as having either high prediabetes if their fasting glucose was between 110 and 125 mg/dL or low prediabetes if their fasting glucose was between 100 and 109 mg/dL. Normoglycemia was defined as a fasting glucose below 100 mg/dL. RESULTS: In multivariable linear regression, adjusted for age, race/ethnicity, menopause transition stage, cigarette use, calcium and vitamin D supplementation, lumbar spine bone mineral density, and study site, women with high prediabetes had 0.21 (p < 0.0001) standard deviations (SD) lower TBS than those with normoglycemia. Low prediabetes was not associated with lower TBS. When HOMA-IR levels were ≥ 1.62, each doubling of HOMA-IR was associated with a 0.11 SD decrement in TBS (p = 0.0001). CONCLUSION: Similar to diabetics, high prediabetics have lower TBS than normoglycemic individuals. Women with greater insulin resistance have lower TBS even in the absence of DM. Future studies should examine the associations of high prediabetes and insulin resistance with incident fracture.