Sleep apnea and femoral neck BMD among Singaporean mid-life women.

Unlabelled: The relationship between sleep apnea and bone health remains controversial. This study explored the relationship between sleep apnea and femoral neck BMD in midlife Asian women. Partner-witnessed apnea predicted higher femoral neck BMD, an effect validated by the STOP index. Our findings suggest that sleep apnea may protect bone health.

Purpose: The menopause transition is associated with decline in bone mineral density (BMD) and sleep quality. However, any relationship between these two factors remains controversial. This study explored the association between sleep apnea and femoral neck BMD in middle-aged women.

Methods: Participants (n = 1201) aged 45-69 years attending well-women visits at the National University Hospital, Singapore were recruited. Self-reported breathing discomfort and snoring, partner-witnessed apnea and snoring were assessed from the Pittsburgh Sleep Quality Index. Femoral neck BMD was assessed with dual-energy X-ray absorptiometry scan and classified into tertiles based on T-scores. Factors reported to affect sleep apnea and bone health in medical literature were potential covariates, p < 0.10. Multivariable ordinal regression analyses assessed associations between sleep measures and BMD. To further validate our findings, we analyzed four sleep apnea characteristics from the STOP questionnaire, a screening tool for sleep apnea. All analyses were performed using SPSS version 20.0.

Results: Mean (SD) age of participants was 56.3 (6.2) years. Partner-witnessed apnea predicted higher BMD tertiles (OR per unit increase in severity 1.39, 95% CI [1.02, 1.89]), independent of age, ethnicity, diabetes, BMI, and handgrip strength. This was further corroborated by the STOP index (OR 1.45, 95% CI [1.07, 1.96]).

Conclusions: This study adds to the literature on sleep apnea and bone health in a non-Caucasian and younger population. Our findings support OSA-associated intermittent hypoxia protecting bone health.