A systematic review and meta-analysis published in Sleep & Breathing evaluated the association between serum levels of 25-hydroxyvitamin D (25OHD) and obstructive sleep apnea syndrome (OSAS). Twenty-four studies were found eligible for this review, including 15 case-control studies and 9 cross-sectional studies, involving a total of 2640 people with OSAS and 933 healthy participants (controls)…