the relationship between severity of obstructive sleep apnea and heart rate variability

background and objective: obstructive sleep apnea syndrome (osas) is a prevalent disease in adults. limited evidence regarding the effect of severity of sleep apnea and depression on heart rate variability (hrv) indices exists. hence, we decided to focus on the association between hrv and severity of osas based on depression score. materials and methods: a total of 193 patients with confirmed osas were selected from a sleep clinic setting. a checklist for demographic data and self-administered questionnaires including the pittsburgh sleep quality index; epworth sleepiness scale; beck depression inventory; snoring, tiredness, observed apnea, blood pressure, body mass index, age, neck circumference (stop-bang), and gender questionnaire were filled in. we used two domains of hrv (e.g., frequency and time) estimation. results: the mean number of pairs of adjacent rr intervals (time between qrs complexes) differing by more than 50 ms in the entire analysis interval (nn50 count) was significantly different among various severity osas groups (μ = 2639.12 ± 478.98 for mild and moderate, and 2313.81 ± 670.54 in severe osas; p = 0.0200). in frequency do-main, the indices were higher in severe osas patients. statistically significant association was between hrv parame-ters (standard deviation of all rr intervals, mean of the standard deviation of all rr intervals for all 5-minutes segments, nn50 count, the nn50 count divided by the total number of all rr intervals, average total power, low frequency power) and osas severity. conclusion: there are some statistically significant differences between osas severity and parameters of hrv.