Effects of age on delta and REM sleep parameters

Sleep EEGs were evaluated in 24 men without medical and psychiatric disease segregated into 3 age groups: 21-30, 31-40, and 51-70 years of age. Sleep was evaluated by 3 different methods: traditional sleep stage scoring, computer-assisted delta and rapid eye movement (REM) quantification, and power spectral analysis. Analysis of manually scored sleep variables revealed that age-related changes in sleep were most pronounced in the oldest age group (51-70). Older subjects spent more time awake, had low sleep efficiency and sleep maintenance, displayed a decreased REM latency, and spent less time in delta sleep. Computer quantification further confirmed that the largest drop in delta activity occurred between the 21-30 and the 31-40 year olds. The largest decrease in delta activity occurred to the greatest extent during the first 100 min of sleep (NREM period 1), and was characterized by a shift in the spectral distribution of power towards higher delta frequencies. Total nighttime REM was increased in the 31-40-year-old group as compared to older and younger subjects. This unexpected non-linear trend may reflect a progressive tendency toward 'lightening' of sleep with increasing age. These studies further suggest that the effects of aging should be incorporated into models aiming at explaining the physiology of sleep.