A study to see association between vitamin d level and obstructive sleep apnea

Abstract

Obese patients have low levels of serum 25-hydroxy vitamin D due to feedback inhibition of hepatic synthesis of the metabolite by increased circulating 1,25(OH) vitamin D. Obese individuals have more physical activity which limits their exposure to sunlight resulting in lower levels of 25(OH)D. Sleep fragmentation in OSA leads to daytime drowsiness, fatigue and hence decreased outdoor activity contributing to the same. Hence, OSA aggravates obesity and obesity aggravates OSA creating a vicious cycle and together contribute to the depletion of serum vitamin D level.Patients attending the special clinic of sleep were included in the study and were screened using STOP-BANG scoring system for OSA Patients with score of >2 were included in the study and further underwent polysomnography test. Among the study population, cases had an apnea-hypopnea index (AHI) > 5 in polysomnography and controls had AHI <5. Controls were further matched for age, sex and BMI with cases. Vitamin D Level was tested in both cases and controls for comparison using arterial blood sample.Total ninety-three patients were included in the study, out of whom 59 were cases which formed the OSA group, had mean age of 48.02 ±8.435 years, mean body mass index (BMI) 33.73 ±7.48 kg/m2, mean neck circumference 37.8 cm ±5.08 Mean vitamin D level in the case and control was 21.02 ± 7.27 and 24.48 ± 6.92 respectively with a p value < 0.05, with a negative correlation of AHI with serum vitamin D level (p< 0.001, r = −0.286).Different mechanisms play a role in OSA patients affecting. This study shows inverse relationship between vitamin D level and AHI (apnea-hypopnea index) which was statistically significant and vitamin D level was higher in controls than cases. Thus it can be said that 25(OH)D levels and OSAS are related, but it is difficult to establish a direct causal association between them.