Changes of vitamin D levels and bone turnover markers after CPAP therapy: a randomized sham‐controlled trial

Abstract

The aim was to investigate whether continuous positive airway pressure treatment could modulate serum vitamin D (25-hydroxyvitamin D) and bone turnover markers (collagen-type 1 cross-linked C-telopeptide, osteocalcin and N-terminal propeptide of type 1 collagen) in secondary analysis from a randomized controlled trial. Sixty-five continuous positive airway pressure-naïve male patients with obstructive sleep apnea (age=49±12years, apnea-hypopnea index=39.9±17.7events h-1 , body mass index=31.3±5.2kgm-2 ) were randomized to receive either real (n=34) or sham (n=31) continuous positive airway pressure for 12weeks. At 12weeks, all participants received real continuous positive airway pressure for an additional 12weeks. After 12weeks of continuous positive airway pressure (real versus sham), there were nobetween-group differences for any of the main outcomes [Δ25-hydroxyvitamin D: -0.80±5.28ngmL-1 (mean±SE) versus 3.08±3.66ngmL-1 , P=0.42; Δcollagen-type 1 cross-linked C-telopeptide: 0.011±0.014ngmL-1 versus -0.004±0.009ngmL-1 , P=0.48; Δosteocalcin: 1.13±1.12ngmL-1 versus 0.46±0.75ng mL-1 , P=0.80; ΔN-terminal propeptide of type 1 collagen: 2.07±3.05μgL-1 versus -1.05±2.13μgL-1 , P=0.48]. There were no further differences in subgroup analyses (continuous positive airway pressure-compliant patients, patients with severe obstructive sleep apnea or sleepy patients). However, after 24weeks irrespective of initial randomization, vitamin D increased in patients with severe obstructive sleep apnea (9.56±5.51ngmL-1 , P=0.045) and in sleepy patients (14.0±4.69ngmL-1 , P=0.007). Also, there was a significant increase in osteocalcin at 24weeks (3.27±1.06ngmL-1 , P=0.01) in compliant patients. We conclude that 12weeks of continuous positive airway pressure did not modulate vitamin D or modulate any of the bone turnover markers compared with sham. However, it is plausible that continuous positive airway pressure may have late beneficial effects on vitamin D levels and bone turnover markers in selected groups of patients with obstructive sleep apnea.