Insomnia can occur in 25–67 % of persons suffering from dementia [3–6]. Guarnieri et al. found recently that the prevalence of insomnia ranged from 44.4 % (in mild cognitive impairment) to 66.7 % (in vascular dementia, Lewy body dementia, and dementia associated with Parkinson disease) with similar prevalence between Alzheimer’s disease (48.5 %) and frontotemporal dementia (48 %) [4]. These findings, confirmed by others [5], were higher than what was described previously [6–8] and are in accordance with our own experience.

Insomnia complaints increase with aging [2–4], and this association with aging is similar to non-dementia populations [1, 2], with no differences between genders. Insomnia is more frequent in subjects with dementia and depressive symptoms [1–3].

Insomnia symptoms may occur in the context of dementia without any other explanation, or as a result of concomitant complaints or associated comorbidity (e.g., pain, cardiorespiratory complaints, depression, or agitation). However, there is a recent and increasing recognition that even when insomnia arises “secondary” to other conditions, it can develop an independent course over time and may remain as a clinically significant condition after the correct treatment of the concomitant comorbidity [9].

In insomnia, sleep–wake difficulty must be differentiated from other types of frequent sleep disorders among patients with dementia (for instance, restless legs syndrome, periodic limb movement disorder, and circadian rhythm sleep–wake disorders). However, insomnia is one of the sleep disorders that more frequently appear in isolation among a population with cognitive impairment and dementia [4] and might emerge at any time over the course of the disease.

The differentiation between insomnia and circadian rhythm sleep–wake disorder (CRSWD) is extremely important as it leads to distinctive management and therapeutic decisions. Difficulty initiating sleep is also present in the delayed sleep–wake phase disorder, and difficulty maintaining sleep with premature morning rise also exists in the advanced sleep–wake phase disorder characteristic of the aging person. Although circadian rhythm disruption leads to insomnia symptoms or excessive daytime sleepiness, an important and distinctive diagnostic criterion of CRSWD is that when patients are allowed to choose their ad libitum schedule, there is an improvement in sleep quality and duration. Patients with neurodegenerative disorders also have an increased risk of another CRSWD called irregular sleep–wake rhythm disorder (ISWRD) [9]. In this case, there is a chronic or recurrent pattern of irregular sleep and wake episodes throughout the 24-h period, characterized by symptoms of insomnia during the night and excessive napping during the day or even both and a clear lack of a prolonged consolidated sleep period with random distribution of sleep periods during the 24-h day. Clinical practice guidelines for the treatment of intrinsic CRSWD, recently published [10], include light therapy, timed oral administration of melatonin or agonists, and combination treatments (with or without accompanying behavioral interventions) with different evidence-based levels and are beyond the scope of this chapter [10]. Nevertheless, these recommendations are firmly against the use of hypnotics to treat elderly patients with ISWRD.

Insomnia can also appear in the context of other behavioral disorders (namely, agitation and psychosis). Sometimes, insomnia is mistaken with difficulty in putting the subject to bed, due to increased motor activity in the evening or through the night.

Severe sleep fragmentation and lower circadian rhythm amplitude frequently coexist with a phenomenon called “sundowning,” which represents an exacerbation of behavioral symptoms, with higher confusion and agitation at the end of the day, usually coincidental with the decrease in daylight, but can start in the late afternoon. The exact meaning of this phenomenon is not known, but it increases the need for surveillance and intervention and might result in the implementation of pharmacological treatment, aimed to control those symptoms.

Insomnia symptoms (whatever the cause) in dementia patients implicate a higher level of burden for caregivers (both formal and informal), leading to higher risk of caregiver exhaustion.

Insomnia can lead to potentially unsafe behaviors like wandering or going out in the middle of the night, with increased risk of falls and other involuntary self-determined injuries, and therefore can be a determinant for institutionalization. Moreover the circularity of the relationship between insomnia and agitation (and other abnormal daytime behavioral symptoms) increases the risk of this type of decision. Insomnia is also associated with higher cognitive decline and depression in cognitive-impaired subjects and higher levels of distress and depression of caregivers. To continue to care for someone who was awake all night and who falls asleep at the end of the morning is a heavy task. So, the clinician needs to approach this problem in a holistic perspective, without excluding the perspective of the caregiver, who is essential for the person suffering from dementia. Although both views are relevant and must be analyzed, before any measures are implemented, caregivers must be aware of the implications of insomnia and the consequences of sleep medications for the patient. However, as we look at the problem, insomnia results in significant caregiver distress, increase in healthcare costs, and increased rates of institutionalization.

A careful interview with the patient and both formal and informal caregivers is essential to understand how and when insomnia symptoms first appeared and their perceived impact and to integrate the symptoms in the whole of the clinical picture. This may require interviewing both the patient and the different caregivers separately, at least over part of the consultation.

Previous personal history on sleep habits needs to be carefully recorded. Was insomnia a previous condition of the patient? Is this symptom present only since the cognitive impairment appeared? How much of the symptom can be explained by changes in habits that were imposed after the diagnosis of dementia?

Are there any precipitants of insomnia? Are there other associated behavioral symptoms? The clinician must bear in mind the dual relation and the interaction between insomnia and other behavioral symptoms. Insomnia might be the cause of next morning agitation and excessive daytime somnolence, but the opposite link might also be true, and insomnia symptoms can be a result of too many daily naps or daily physical inactivity or even the consequence of medication aimed to control agitation over the day. This general approach, together with careful questioning on the circumstances of the specific behavior, may be crucial to identify the precipitant of insomnia symptoms.

When the patient has changed their living place (for instance, into a relative’s home) or is in a nursing home, it is crucial to collect the habits in the new living place and to compare to previous sleep habits. Many times insomnia symptoms are associated with a different type of routine, not only in the expected time asleep but also might be mediated through a change in their own routines at time of going to bed. Frequently, patients suffering from dementia have different caregivers, even when they live in their own home, as some caregivers (formal or informal) rotate over the week. Changes in routine when caring for a person with dementia can cause instability and lead to difficulty falling asleep. Another aspect is to verify environmental changes that might be simple details, such as uncomfortable room temperature, uncomfortable clothes used (such as removing socks in patients who are accustomed to wearing socks at night), and unusual noise.

Daily routines and activities should also be evaluated, namely, habits that increase the risk of insomnia symptoms, such as low exposure to light, physical inactivity, repeated or long naps over the day, and irregular starting of bedtime routines.

Other behavioral changes can interfere with the moment of falling asleep, such as visual hallucinations, agitation, or misinterpretations of the caregiver or spouse. Agitation and psychosis are approached, respectively, in Chap. 9 and in Chap. 10, and workout of each of them might also solve insomnia symptoms. In other cases, insomnia is the cause of agitation.

Insomnia symptoms might be due to a comorbidity unrelated with dementia, for instance, pain or general medical disorders that might interfere with sleep, such as cardiac diseases or respiratory problems, or neurological disorders like restless legs syndrome, periodic limb movement disorder, or REM behavior disorder. A careful medical history and physical examination should be conducted prior to considering any treatment. Directed treatment for the particular condition (whenever identified) should be started. If another sleep disorder is diagnosed, although treatment of the primary disorder is desired, caution must be applied in the choice of the treatment. Whenever possible, the decision must take into account the cognitive diagnosis as well (this is detailed further in the treatment section of this chapter). Clinical depression and anxiety must be ruled out, and in the event that insomnia is a symptom of depression or anxiety, these must be directly treated.

Medication should be carefully reviewed, not only medication associated with cognitive disorder but also other medications that can be disruptive for sleep integrity.

Some drugs are associated with a higher risk of insomnia, such as antiparkinsonian drugs (e.g., dopamine agonists, amantadine), some antidepressants (like selective serotonin reuptake inhibitors (SSRI), moclobemide, bupropion – particularly during the initial phases of treatment – among others), corticosteroids, bronchodilators, and even benzodiazepines that can cause an idiosyncratic effect and paradoxically induced agitation instead of a better sleep profile. Review of daily drugs that might induce somnolence (analgesics, antihistaminic) is needed. Alcohol consumption must be cautiously evaluated, as it can be associated with sleep problems.