The two-process model of sleep regulation. Figure 1 shows a schematic diagram of Process S and Process C in a healthy younger adult (Panel A), and an older adult with reduced circadian rhythm amplitude and earlier timing with alterations in sleep homeostasis (Panel B). Also, the timing of circadian rhythms typically shifts to an earlier time, which can result in sleepiness at undesirable times (e.g., at 6 p.m.). In particular, circadian rhythm amplitude is reduced, which may result in a weaker daytime “alerting signal” from the biological clock. If the person then naps, the homeostatic drive will be reduced at night.Įndogenous circadian rhythms (Process C) also change in timing and quality with advancing age. First, as sleep architecture changes and the ability to sleep solidly at night decreases, the homeostatic drive for sleep (Process S) may increase during the daytime hours.
The two-process model can be used to conceptualize sleep disturbance in older adults. Sleep Regulation in Older Adults: The Two-Process ModelĪccording to the two-process model of sleep regulation ( Borbely, 1982), two biological mechanisms control sleep: the homeostatic drive for sleep (Process S), that is, the longer one is awake, the more likely one is to fall asleep and the circadian drive for sleep (Process C), a separate process by which the propensity for sleep varies across the 24-hour day. Practical recommendations are summarized in Table 1. Clinical considerations on adapting CBT-I for older adults (and for the particular case discussed) are presented in the clinical practices and summary section. A case illustration of an older patient with insomnia and early morning awakenings follows a description of the gold-standard behavioral treatment for insomnia: cognitive behavioral therapy for insomnia (CBT-I). We then discuss the two-process model of sleep regulation ( Borbely, 1982) as it applies to sleep disturbances in advanced age. In this article, we briefly describe insomnia and common sleep problems in older adults. This can devolve into a vicious cycle in which napping then leads to even more nighttime insomnia. Insufficient nighttime sleep then contributes to daytime sleepiness and may lead to daytime napping. In inpatient settings (e.g., hospitals, nursing homes), environmental factors such as noise and light also disrupt sleep. Among older adults, nocturia or arthritis pain can disrupt nighttime sleep. Individuals with untreated sleep apnea are sleepier during the day than people without sleep apnea or people with treated sleep apnea. Most primary sleep disorders (e.g., sleep apnea) increase in prevalence with advancing age. Because older people spend less time in the deeper stages of sleep and more time in the lighter stages of sleep, they are more likely to awaken, for example, from noise in the environment. Sleep latency (time to fall asleep) increases, early morning awakenings are more common, deep sleep (stages 3–4) decreases, and sleep efficiency (time asleep while in bed) is reduced. One reason older adults may be at higher risk for insomnia is that sleep itself changes with advancing age. Healthy older adults have rates of insomnia similar to the overall adult population. Importantly, older adults with medical conditions and depression are particularly at risk for insomnia. Rates among older adults appear much higher, with some studies showing rates as high as 40%. Studies estimate that the prevalence of insomnia in the general population ranges from 10 to 20%. Insomnia can be transient, lasting a few days or weeks however, many older adults experience insomnia for years. Sleep-onset insomnia (difficulty falling asleep) is most common in younger adults, whereas sleep maintenance insomnia (difficulty staying asleep) and early morning awakening are more common in older adults ( Lichstein, Durrence, Riedel, Taylor, & Bush, 2004). This is particularly relevant among older adults because about 70% of older adults with insomnia have comorbid psychiatric disorders, medical conditions, take medications that impact sleep or use alcohol or drugs ( National Institutes of Health, 2005). It is often difficult to ascertain whether insomnia is “primary” or “secondary” to another condition however, research suggests that insomnia can be successfully treated in either case. Insomnia can be an independent disorder (primary insomnia) or attributed to another condition (secondary insomnia American Academy of Sleep Medicine, 2005 American Psychiatric Association, 1994). Insomnia is a complaint of poor sleep that, for some people, reaches the level of a disorder worthy of treatment.
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