Sleep-Disordered Breathing and Decreased Bone Mineral Density: Masking Effects of Body Mass Index

The relationship between sleep-disordered breathing (SDB), bone mineral density (BMD), and risk of osteoporosis is unclear. Obesity, a condition often comorbid with SDB, has been associated with high BMD, yet its impact on bone health remains controversial. The purpose of this study was to evaluate the implications of obesity in the relationship between SDB and BMD.

A total of 225 adults aged 20-65 years were enrolled in this study. Participants were nonsmokers, free of major cardiovascular diseases, and not receiving treatment for SDB. Participants completed overnight polysomnography and whole-body dual-energy X-ray absorptiometry (DEXA) scans. SDB was defined as apnea-hypopnea index of ≥5 events/hour. Total body BMD (g/cm2), T scores, and Z scores were obtained from DEXA scans. Height and weight measures were collected for computation of body mass index (BMI, kg/m2). Multivariable linear regression analysis was conducted to test the association between SDB and BMD metrics and the contribution of relevant covariates.

Participants with SDB (n = 74, 32.9% of the sample) had higher total-body BMD (p = 0.003), T score (p = 0.017), and Z score (p = 0.011) compared to non-SDB controls. In multivariable models adjusted for demographic characteristics, SDB was not significantly associated with total-body bone measures. However, when including BMI, significant inverse relationships between SDB and total body BMD (p = 0.046), T score (p = 0.049), and Z score (p = 0.049) became apparent. Such associations persisted after controlling for lifestyle, clinical and sleep variables (fully adjusted models, total BMD, p = 0.036; T score, p = 0.037; Z score, p = 0.034). In sensitivity analysis, there were no associations between SDB and bone measures in models adjusted for body fat in lieu of BMI.

An inverse, albeit modest, association between SDB and BMD exists, and this relationship emerges when considering BMI but not body fat. Hence, our data suggest that elevated body mass rather than adiposity may mask the negative association between SDB and bone health, thus possibly explaining prior conflicting evidence. Longitudinal investigations corroborating these findings and evaluating their implications for osteoporosis risk in patients with SDB are needed.