Sleep Disorders in Dementia

Restless legs syndrome (RLS) is characterized by a compelling urge to move the legs during periods of inactivity with worsening that occurs during the evening. Commonly, there are parasthesias with uncomfort­able or unpleasant feeling in the legs while immobile that is relieved by movement of the limb. Although technically a disorder of wakefulness, RLS enters this discussion of sleep disorders because of the impact on the ability to transition into sleep. Ferritin levels less than 50 ng/mL, neuropa­thy, and renal failure are common risk factors. Certain medications like antidepressants or antihistamines may aggravate or trigger this condition. A positive response to dopaminergic agents is oftentimes considered to be supportive evidence. Iron replacement may improve symptoms in indi­viduals with low ferritin levels. Antipsychotics and other dopaminergic antagonists may lead to the development of akasthesias or restlessness that may be quite similar in presentation. Treatment usually consists of addressing possible aggravating factors and then the use of either dop­aminergic agents, selected anticonvulsants, benzodiazepines, or opioids. Since the diagnosis is largely based on the description of a subjective expe­rience, there may be particular problems with diagnosis in the cognitively impaired population.

Periodic limb movements (PLMs) are brief, repetitive, and stereotyped movements of the limbs that occur every 5 to 90 seconds at a frequency of at least 15 limb movements per hour. These are not problematic unless they are associated with RLS symptoms, causing arousals and daytime symptoms, or affecting the sleep of bed partners. There are no FDA recom­mended treatments for PLMs at this time.

The parasomnia that is of particular interest in the discussion of sleep in dementia is REM behavior disorder (RBD). RBD occurs when there is a loss of the normal REM atonia leading to complex motor activity dur­ing REM sleep with an apparent acting out of often violent dreams. This may occur in the normal population, though usually an older popula­tion, and it may be triggered by certain medications like antidepressants. Although RBD has also been associated with brainstem lesions, especially those involving the pons, it has been particularly associated with the group of neurodegenerative disorders referred to as synucleinopathies. RBD may actually precede the emergence of other symptoms of this group of degenerative disorders by several years. Treatment starts with ensuring the safety of the patient and the bed partner if there is a con­cern for injury. Removal of aggravating factors or medications may be helpful. Clonazepam and/or melatonin can also be used for the treat­ment of RBD.

Excessive daytime sleepiness (EDS) may be attributed to disrupted or inadequate nocturnal sleep, but may also be related to hypersomnia with an increased need for sleep during a 24-hour period. At times, hypersom­nia may be a component of neurodegenerative dementias, but medica­tions and depression need to also be considered as causes of hypersomnia in this population. Depression, in particular, is often overlooked as a cause of hypersomnia in the group of patients.

I nsomnia, on the other hand, is described as an inability to initiate or maintain sleep with resultant daytime dysfunction, in the setting of appropriate sleep opportunity and sleep environment. Many medical fac­tors need to be considered in the assessment of insomnia, especially in the older patient where medications, pain problems, and urges to urinate through the night need to be considered. Anxiety is another factor that may contribute to insomnia and is one that is often overlooked, especially in a cognitively impaired patient. Many patients suffering from insomnia considered to be idiopathic or primary actually suffer from a degree of anxiety that may not reach criteria for a formal diagnosis of an anxiety dis­order. Obviously, these issues may be difficult to delineate in a cognitively impaired patient.

Sleep-disordered breathing refers to obstructive sleep apnea (OSA) and central sleep apnea (CSA). Obstructive sleep apnea occurs in the setting of a sleep-related obstruction, either in the nasopharynx or hypopharynx, which causes decreased airflow in spite of breathing effort. The obstruc­tion is usually a function of the anatomy of the individual’s upper air­way and the degree of muscle relaxation that occurs during sleep. Central sleep apnea is characterized by a pause in breathing related to absent breathing effort. Diagnosis usually requires confirmation with a formal polysomnogram or overnight sleep study. Sleep-disordered breathing is often associated with hypoxemia, fragmented sleep, and excessive day­time sleepiness. Recently an association with hypertension, impaired glu­cose, heart failure, pulmonary hypertension, and motor vehicle accidents has been established. The treatment of OSA is commonly with positive airway pressure, oral appliances, surgery (maxilla-mandibular advance­ment), or tracheostomy. Since obesity and supine sleeping position may be aggravating factors, weight reduction and attention to sleep position may also play a role in the treatment of OSA. CSA may be caused by excessive opioid use, congestive heart failure, or other CNS disorders. Treatment of underlying factors, when possible, is recommended. There may also be a role for modifications of the positive airway pressure systems.

Sleep derangements can have a detrimental effect on patients with dementia and their caregivers. The effect of poor sleep on an individual’s health and cognition is profound. Poor sleep is also a risk factor for institu­tionalization of the elderly with dementia because of the negative impact on the care giver.