Vitamin D status of male OSAS patients improved after long-term CPAP treatment mainly in obese subjects

Objective The aim of this study was to evaluate the effect of one-year useful continuous positive airway pressure (CPAP) treatment on serum vitamin D levels in middle-aged men affected by obstructive sleep apnea syndrome (OSAS). Methods This is a secondary investigation related to a previously published observational study about the effect of short-term CPAP therapy on serum vitamin D levels in severe OSAS (Apnea-Hypopnea Index – AHI- >30/h) patients. In the present study, we included patients participating to the previous investigation who repeated serum vitamin D assessment after one year of useful CPAP treatment, and compared to control a group of OSAS patients with scarce compliance to CPAP treatment. OSAS patients with beneficial use of CPAP treatment were distributed in obese (Body Mass Index – BMI ≥30) and non-obese (BMI < 30). Moreover, the mean change between baseline and one-year follow-up (Δ) of serum vitamin D levels was correlated with demographic, polygraphic and clinical data throughout a multiple regression analysis. Results We documented the significant increase of serum vitamin D levels after one year of CPAP treatment in the OSAS group (n = 39, p < 0.001) and in both subgroups of obese (n = 23, p < 0.01) and non-obese (n = 16, p < 0.01) OSAS patients. Conversely, OSAS patients with a scarce compliance to CPAP therapy did not change serum vitamin D levels after one year (n = 10, p > 0.05). OSAS patients with beneficial CPAP treatment showed higher vitamin D serum levels after one year and a more frequent shift from insufficient to sufficient vitamin D status compared to OSAS patients not adequately using CPAP treatment. In particular, the obese OSAS patients subgroup shifted from insufficient (≤20 ng/mL) to sufficient (>20 ng/mL) vitamin D status after CPAP therapy more than the non-obese OSAS patients subgroup (p < 0.05). We observed higher Δ of vitamin D serum levels, Epworth Sleepiness Scale score, and AHI in obese compared to non-obese OSAS patients. Finally, BMI obtained at baseline positively correlated with Δ of vitamin D serum levels. Discussion This study documented that long-term CPAP treatment is a viable therapeutic choice for correcting both sleep apnea condition and vitamin D deficiency in middle-aged male OSAS patients. Significantly, this effect was more evident in obese subjects and possibly represents a valid therapeutic strategy to ensure sufficient vitamin D levels in these patients, which frequently show a deficient vitamin D status