Sleep Restriction with Circadian Disruption Negatively Alter Bone Turnover Markers in Women.

PURPOSE: Determine if an uncoupling of bone turnover markers (BTMs) occurs in women exposed to the combination of sleep restriction with circadian disruption (SRCD), as previously reported in men. METHODS: Four bone biomarkers (N-terminal propeptide of type I procollagen [P1NP] and osteocalcin=bone formation; C-telopeptide [CTX]=bone resorption; sclerostin=bone formation inhibitor) were measured in bihourly samples over 24-h at baseline and after ~3 weeks of sleep restriction (~5.6h sleep/24h) with concurrent circadian disruption (SRCD, recurring 28-h 'day' in dim light). Maximum likelihood estimation in a repeated measures model was used to assess the effects of SRCD and age on bone biomarkers. RESULTS: Five women were young (22 ± 2.8 years) and four were older (58 ± 1.8 years). Baseline bone biomarker levels did not differ by age (all p ≥ 0.07). Bone formation markers were lower after SRCD (estimate ± SEE, ∆P1NP = -9.5 ± 2.8 ug/L, p=0.01; ∆Osteocalcin = -2.3 ± 0.9 ng/mL, p = 0.04). The P1NP decline was greater in young women (∆P1NP = -12.9 ± 3.7 ug/L, p = 0.01). After SRCD, CTX was significantly higher in young women (0.182 ± 0.069 ng/mL, p = 0.04) but did not change in older women. CONCLUSIONS: These pilot data are similar to previous findings in men and suggest that SRCD negatively altered bone metabolism in women by decreasing markers of bone formation and, in young women, increasing a marker of bone resorption. If sustained, this pattern of BTM uncoupling may lead to bone loss and lower bone mineral density.