Unique sleep-stage transitions determined by obstructive sleep apnea severity, age and gender

Abstract

In obstructive sleep apnea, patients’ sleep is fragmented leading to excessive daytime sleepiness and comorbidities like arterial hypertension. However, traditional metrics are not always directly correlated with daytime sleepiness and the association between traditional sleep quality metrics like sleep duration and arterial hypertension is still ambiguous. In a development cohort, we analyzed hypnograms from mild (n=213), moderate (n=235) and severe (n=277) OSA patients as well as healthy controls (n=105) from the European Sleep Apnea Database (ESADA). We assessed sleep by the analysis of two-step transitions depending on OSA severity and anthropometric factors. Two-step transition patterns were examined for an association to arterial hypertension or daytime sleepiness. We also tested cumulative distributions of wake as well as sleep states for power laws (exponent α) and exponential distributions (decay time τ) in dependency on OSA severity and potential confounders. Independent of OSA severity and potential confounders, wake state durations followed a power-law distribution, while sleep state durations were characterized by an exponential distribution. Sleep stage transitions are influenced by OSA severity, age and gender. N2→N3→wake transitions were associated with high diastolic blood pressure. We observed higher frequencies of alternating (symmetric) patterns (e.g. N2→N1→N2, N2→wake→N2) in sleepy patients both in the development cohort and in a validation cohort (n=425). In conclusion, effects of OSA severity and potential confounders on sleep architecture are small, but transition patterns still link sleep fragmentation directly to OSA-related clinical outcomes like arterial hypertension and daytime sleepiness.