Approximately 37 million Americans are 65 years of age or older, representing 12.5% of the national population. The next 20 plus years will see a remarkable shift in the older adult population (Fig. 1). By 2030, 20% of the U.S. population, one in five persons, will be aged 65 or older, a near doubling of the present ratio of one in nine persons. This radical population shift in the proportion of older adults will have a massive negative impact on our already strained health-care systems.
Of the many major physiological changes that accompany the aging process, one change that is typically problematic for many is an often profound disruption of an older adult’s daily sleep–wake cycle. Epidemiological studies have consistently shown that the prevalence of significant sleep complaints grows steadily with advancing age.
Some 57% of adults over the age of 60 complain of significant sleep disruption, 45% have periodic limb movements during sleep (PLMS), 29% have insomnia, 24% have obstructive sleep apnea (OSA), 19% complain of early morning awakening, and 12% have restless legs syndrome (RLS). Only a minority of patients described no sleep complaints in survey of over 9000 participants aged 65 years and older in the National Institute on Aging’s multicentered study entitled “Established Populations for Epidemiologic Studies of the Elderly” (EPESE). The majority of patients described difficulties initiating sleep, nocturnal awakenings, insomnia, daytime napping, troubles falling asleep, waking up too early in the morning, and waking up too early without feeling rested (Fig. 2) (Foley DJ, Monjan AA, et al. Sleep complaints among elderly persons: An epidemiologic study of three communities. Sleep 1995; 18(6):425–432.). While sleep disturbances can have profound implications for an individual’s health, the nature of these disruptions is complex.
The most striking change in sleep in older adults is the repeated and frequent interruption of sleep by long periods of wakefulness, possibly the result of an age-dependent intrinsic change in sleep homeostatic processes. This age-dependent increase of nighttime wakefulness, as well as other well-characterized sleep–wake changes, is mirrored by increases in daytime fatigue, excessive daytime sleepiness and increased likelihood of napping, or falling asleep during the day.
Aging is also associated with a tendency to both fall asleep and awaken earlier and to be less tolerant of phase shifts in time of the sleep–wake schedule such as those produced by jet lag and shift work. These changes suggest an age-dependent breakdown of the normal adult circadian sleep–wake cycle.