29 Apr What is normal sleep?
We currently understand that sleep architecture changes as we age. With large amount of sleep time consisting of mostly deep sleep (slow wave sleep – SWS) and dreaming sleep (REM sleep) in young children transitioning to having less and less proportions of SWS as we age through and past middle age. The total sleep time is also thought to decrease as we age, leading to a proportionate decrease in total time spent in REM sleep. However our understanding of what is indeed normal may be changing.
Boulos et al. recently published their meta-analysis in the Lancet in April 2019 that looked at the normal sleep parameters recorded during type 1 sleep studies, type 1 polysomnography is the highest quality type of sleep study. They found that while changes do occur as we age, particularly the total sleep time, these are not seemingly as significant as we had previously thought. As we age, the percentage of N2 sleep (0·0%, 95% CI −0·1 to 0·1), SWS sleep (−0·1%, −0·1 to 0·0), and REM sleep (0·0%, −0·1 to 0·0) were not found to be significant. For each decade of age, total sleep time decreased by 10·1 min (95% CI 7·5 to 12·8), sleep efficiency decreased by 2·1% (1·5 to 2·6), wake after sleep onset increased by 9·7 min (6·9 to 12·4), sleep onset latency increased by 1·1 min (0·3 to 1·9), arousal index increased by 2·1 events per h (1·5 to 2·6), percentage of N1 sleep increased by 0·5% (0·1 to 0·8). So our sleep does deteriorate in quality and quantity as we age, but the architecture seemingly remains somewhat consistent.
Original article can be found here:
https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(19)30057-8/fulltext