Association between serum vitamin D and obstructive sleep apnea syndrome in children: a case–control study

Purpose To measure serum 25-hydroxyvitamin D [25(OH)D] levels in children with obstructive sleep apnea syndrome (OSAS) and to evaluate the correlation between vitamin D status and disease severity. Methods A case–control study was conducted at the Otorhinolaryngology outpatient clinics of Ain Shams University Hospitals, Cairo, Egypt. Children aged 2–16 years were screened using the validated Arabic version of the Sleep-Related Breathing Disorder scale of the Pediatric Sleep Questionnaire (SRBD-PSQ). Participants with SRBD-PSQ scores ≥ 33% ( n = 42) formed the OSAS group and those with scores < 33% ( n = 42) served as controls. Serum 25(OH)D was quantified by competitive inhibition ELISA. Groups were matched for age, sex, and BMI. Results Both groups were comparable for age, sex, and BMI (all p > 0.05). Mean serum 25(OH)D was significantly lower in OSAS cases than controls (23.94 ± 9.33 vs. 28.18 ± 9.83 ng/mL; p = 0.021). Severe deficiency (< 20 ng/mL) was present in 47.6% of cases versus 9.5% of controls ( p = 0.001). Serum 25(OH)D correlated inversely with SRBD-PSQ scores in cases (rₛ = −0.487; p = 0.006) and controls (rₛ = −0.526; p = 0.002). Conclusion Serum 25(OH)D was significantly lower in Egyptian children with likely OSAS (screened by SRBD-PSQ) than in matched healthy peers. The inverse correlation between vitamin D status and SRBD-PSQ severity score is consistent with an association between hypovitaminosis D and pediatric sleep-disordered breathing; however, causality cannot be inferred from this cross-sectional design. Prospective studies incorporating polysomnography are needed before vitamin D measurement can be recommended as a clinical adjunct in OSAS evaluation.