Derk-Jan Dijk, from University of Surrey (Guildford, United Kingdom), and colleagues investigated whether age impacts slow-wave sleep and sleep continuity, and whether aging men and women experience increased daytime sleepiness. The team enrolled 110 healthy adults without sleep disorders or sleep complaints; 44 were ages 20 to 30 years, 35 were ages 40 to 55 years, and 31 were ages 66 to 83 years. During a night of eight hours in bed, total sleep time decreased significantly and progressively with age. Older adults slept about 20 minutes less than middle-aged adults, who slept 23 minutes less than young adults. The number of awakenings and the amount of time spent awake after initial sleep onset increased significantly with age, and the amount of time spent in deep, slow-wave sleep decreased across age groups. Yet even with these decreases in sleep time, intensity and continuity, older adults displayed less subjective and objective daytime sleep propensity than younger adults. The team concludes that: “Healthy aging is associated with a reduction in daytime sleep propensity, sleep continuity, and slow-wave sleep … [which] may reflect a lessening in homeostatic sleep requirement. Healthy older adults without sleep disorders can expect to be less sleepy during the daytime than young adults.”
