People with dementia tend to have bad sleep and insomniacs are more likely to develop dementia.
Dementia broadly comprises of a cohort of pathophysiological conditions, including Alzheimer's disease, vascular dementia, Lewy body dementia, Parkinson's disease, Huntingdon's disease, alcohol-related dementia, AIDS-related dementia and Creutzfeldt-Jakob (or Prion) disease. Common symptoms include progressive loss of cognitive powers like memory, social skills and compromised normal emotional reactions. Alzheimer’s disease, the most common form of dementia, is characterized by decreased production of the acetylcholine neurotransmitter and a progressive loss of cognitive functions. About 5.1 million Americans have Alzheimer’s disease and the number is projected to increase to 14 million by 2050.
Three categories of people are at a heightened risk of dementia: the elderly, patients with neurodegenerative diseases, and patients with mild cognitive impairment. Although 40% of elderly patients have sleep-related complaints, bad sleeping disorders are less common and are more often associated with co-morbidities.
Sleep disorders such as REM sleep behavior disorder (RBD), restless legs syndrome (RLS), periodic limb movements (PLMs) and sleep-disordered breathing become more prevalent with increasing age. RBD and sleep apnea are of particular interest with regard to dementia.. RBD is used as a contraindication of Lewy body dementia and are used as prognostic and predictive tools for neurodegeneration in Parkinson's disease. Similarly, obstructive sleep apnea (OSA) reportedly has common casual factors with Alzheimer’s disease and has been proposed to contribute to the pathophysiology of Alzheimer’s.
Troubled sleep is common in patients with dementia. Using interviews and polysomnograms scientists found longer sleep latency, increased sleep fragmentation, and decreased sleep efficiency (decreased slow wave sleep) and total sleep time in dementia patients. The most common sleep disorder symptoms in patients with dementia are increased daytime sleepiness, nighttime wandering, confusion, and agitation (sundowning). Nobody understands the origin of or the mechanism of the sundowning phenomenon many patients in institutions exhibit, but some suspect it could be related to the early circadian cycle of seniors and the recently discovered biological clock that starts operating in the brains of older people.
The clinical presentation of sleep disorders in demented patients is progressively less stage 3 and REM sleep and increasing nighttime awakenings. The increase in REM latency found in patients with dementia can be attributed to the overall reduction of the REM phase. Neuronal degeneration in Alzheimer's contributes to the sleep pattern changes by damaging the basal forebrain and the reticular formation of the brainstem, two regions implicated for regulation of sleep patterns. Recently, a-synuclein aggregates have been attributed to cause dementia. The synuclein proteins are normally present in synapses of nerve terminals in the brain.
An estimated 30-50% of Parkinson’s Disease patients have excessive daytime sleepiness, a percentage that is higher at more advanced stages of the disease. Parkinson's patients often have insomnia that comes and goes through the course of the disease. A recent study found seniors with sleep problems tend to have beta-amyloid plaques in their brains more often than good sleepers. Even in elderly patients without diagnosed Alzheimer's the characteristic plaques have been found often in the brains of insomniacs.
Dementia afflicted patients often suffer from sleep apnea. A study conducted in patients with dementia showed that severe sleep apnea is directly correlated to induction of severe dementia and vice versa. Even though sleep apnea does not directly cause dementia, the sundowning effects and persistent hypoxic conditions can symptomatically amplify dementia. Sleep disordered breathing episodes are quite common, with 90% of persons with moderate-to-severe Alzheimer's suffering at least five respiratory events per hour of sleep. The overall prevalence of SDB in patients of dementia varies between 33% and 70%. A recent study suggests a possible link between sleep deprivation and increased risk for Alzheimer's. Levels of amyloid-beta protein in the bloodstream rise during waking periods and decline during sleep. This protein makes up some of the brain plaques that Alzheimer's patients seem to have.
Problem sleep can be an early indicator of dementia. Alzheimer's patients often see changes in their sleep patterns early in their diseases - what had been 20 minute daytime naps stretch to several hours. Analysis of people in a long-term longitudinal study found that older people who complained of daytime sleepiness, restless nights, and increased use of sleep aid medication were much more likely to get Alzheimer's within two years. The Canadian researcher who did this analysis said sleep problems were the single strongest early predictor of this form of dementia. Alzheimer's is not well understood but scientists modified mice to put characteristic amyloid-ß plaques in their brains and found a disruption in the sleep cycle. When the plaques were removed from this murine model. sleep returned to normal.
There is no cure for dementia and related sleep disorders but medications and disciplined lifestyle can alleviate the most severe persistent conditions. Medications can improve cognitive function for some with dementia. There has been little research done on directly addressing insomnia with medication for these patients, and a meta-study by the UK’s Cochrane Group found "there is very little evidence to guide decisions about medicines for sleeping problems in" those with Alzheimer’s.
Sleep-disordered breathing (SDB) is usually treated with continuous positive airway pressure (CPAP) machines. A rule of thumb home health care practitioners have developed is that patients with dementia can tolerate up to five hours of CPAP per night. In this cohort of patients, CPAP decreased the incidence of SDB episodes from 24 to 10 per hour at nighttime. CPAP treatment also decreased daytime sleepiness and there are some indications that CPAP retards cognitive impairment in demented patients. Institutional caregivers have self-reported that CPAP treatment decreased snoring and caused mood elevations and overall quality of life.
Taking a cue from the observed correlation between circadian rhythms, agitation, and light exposure in demented patients, cutting edge doctors have started using therapeutic strategies with bright light exposure to regularize sleep patterns. Melatonin and melatonin agonists are also attracting a lot of attention and interest in treatment not just for insomnia, but as an overall treatment to address many symptoms of Alzheimer's.
Experts recommend caregivers and family members take safety precautions to prevent risk of injury during sleep. This includes removing dangerous objects such as weapons from the bedroom, locking all doors and windows, and following up regularly with a doctor to monitor for signs of brain degenerating diseases. Caregivers are also advised to become familiar with signs of dementia, Parkinson's or multiple system atrophy. A healthy diet and well-defined daytime routine involving light to moderate physical exercise contributes to the overall well-being. In some institutionalized care facilities like nursing homes, sedatives are given to ensure nighttime sleep. But cognitive functions are further compromised by sedative usage so this should be avoided if possible.
The high incidence of SDB in demented patients is contraindicative that neuronal damage contributes to the respiratory problems during sleep, and in turn contributes to the cognitive impairment seen in dementia. More research is required to effectively characterize the nature, severity and etiology of sleep disorders in demented patients and to answer the paradoxical question of whether dementia lead to sleep disorder or vice versa.