A preliminary study of factors influencing the occurrence of post-arousal hypersynchrony

Abstract Background Post-arousal hypersynchrony (PAH) is a continuous delta wave occurring after arousal. We hypothesized that PAH would decrease with age because PAH is affected by sleep pressure, which decreases with age. Methods We evaluated polysomnography (PSG) during daytime napping to determine whether age affected the incidence of PAH. Twenty healthy participants (10 females, 45.0 ± 14.8 years [mean ± standard deviation], and age range, 22-67 years) were assessed using PSG during 90-min naps. PAH was present in two participants in their 20 s, one in their 40 s, and two in their 60 s. We first investigated whether the incidence of PAHs decreases with age using correlation analysis. Secondly, correlations between PAH and sleep index were analyzed to evaluate the factors influencing PAH occurrence. Thirdly, we evaluated whether sleep pressure decreases with age. %N3 and slow-wave activity (SWA) were used to measure sleep pressure. Results PAH occurrence was unchanged with age. PAH corrected with total sleep time (PAH/TST) increased with %N3, but not with SWA. PAH/arousal, which is PAH corrected by the number of arousals, was also increased with %N3 and SWA. These results indicate that PAH occurrence may be related to sleep pressure. Contrary to expectation, %N3 showed no change with age, but SWA decreased with age. Conclusions PAH occurrence may be affected by sleep pressure. Contrary to our hypothesis, PAH was seen in older adults, and its occurrence was unchanged with age. This may be associated with the relatively high sleep pressure observed in older adults.