One of the major symptoms of dementia is insomnia and other sleep disturbances. Bright light therapy has been shown to work effectively in treating impaired circadian rhythms and may be a beneficial adjuvant therapy in treating sleep disturbances in dementia.
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What is bright light therapy?
Bright light therapy is a form of therapy in which patients are exposed to daylight or the equivalent of daylight by using a special lamp. Most commonly, bright light therapy is used in the treatment of seasonal affective disorder (SAD), a form of seasonal depression that occurs primarily during the winter months and is characterized by sleep and mood disturbances.
Reduced daylight in the winter months affecting melatonin production may be an important factor in the cause of SAD. The extra darkness favors increased melatonin production affecting mood, energy and sleep in susceptible individuals. Bright light therapy, therefore, inhibits extra melatonin production in addition to increasing synaptic serotonin in retinofugal pathways in the midbrain. Thus, artificially exposing individuals to either bright white full spectrum light (10,000lux); or at different wavelengths, at a usual distance of 30-60cm (from the eyes at a 30O angle) for around 30-60 minutes is a very safe and effective treatment for SAD.
it is important to note that in some individuals bright light therapy alone is not sufficient to treat SAD but can work for a large proportion of mild-moderate SAD patients. Furthermore, using bright light therapy first thing in the morning may be the most effective time to reset circadian rhythms thus alleviating some of the depressive symptoms associated with SAD.
Perhaps one of the biggest benefits of bright light therapy is that it is a safe and easy method in the potential treatment of SAD and other related disorders, even if does not work for some people depending on the patient’s routine and preference of treatment. Furthermore, bright light therapy may also be useful as an adjuvant therapy in people with major depression and bipolar disorder alongside pharmacological and cognitive therapies.
Bright light therapy & dementia
Dementia refers to a group of symptoms and disorders that affect cognition impacting activities of daily living. The most common cause of dementia is Alzheimer’s disease, in addition to vascular dementia, dementia with Lewy bodies (DLB) and frontotemporal dementia (FTD). Whilst these diseases have different causes and mechanisms, many of the cognitive symptoms are similar. Parkinson’s disease and amyotrophic lateral sclerosis can also lead to dementia relating to DLB and FTD respectively.
One of the main symptoms of dementia after impaired cognition is that of sleep disturbances. The most problematic sleep disturbances are found in Alzheimer’s disease and DLB, and less so in vascular dementia. Usually, hypnotic medications are prescribed for the treatment of sleep disturbances, however, these usually come with common negative side effects (including additional amnesia and increased rates of falling). Given the effectiveness of bright light therapy in the treatment of SAD and other non-seasonal depression (especially sleep disturbances), it may be a safe and easy method in the treatment of sleep disturbances in dementia.
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Studies using bright light therapy in Alzheimer’s patients have found that the therapy is effective in treating sleep disturbances, but only in those with a shorter duration of disease and those at a mild-moderate stage of disease compared to those with more advanced dementia. This took on average 5-11 days to work for Alzheimer’s patients. One of the biggest issues with using bright light therapy in Alzheimer’s patients was poor compliance; however, sleep disturbances still improved in less compliant Alzheimer’s patients.
With respect to vascular dementia, there was no significant effect of bright light therapy. However, unlike Alzheimer’s disease, vascular dementia is considerably more variable depending on the sites most affected within the brain thus giving rise to different subsets of disease. With respect to DLB, again there was no significant improvement in sleep disturbances by bright light therapy (given that sleep disturbances are most common in DLB). This is because the cause of sleep disturbances in DBL is different from Alzheimer’s and has less to do with melatonin, and more to do with Parkinsonian symptoms and dopaminergic impairments.
Another recent study used daily bright light therapy (10,000lux) for 3 consecutive weeks in 37 institutionalized patients (aged 70-93 years). Baseline measures were obtained prior to therapy and daily assessments were made throughout the period. This study found a significant improvement in sleep (nocturnal insomnia, diurnal hypersomnia and sleep quality), in addition to general cognitive abilities (memory and functional state) with 90 minutes of therapy for as little as 5 days by improving their circadian rhythms.
In summary, bright light therapy may be a safe and effective adjuvant therapy strategy in the treatment of sleep disturbances in mild-moderate Alzheimer’s disease, but less so for other forms of dementia such as vascular dementia and DLB. However, more research using larger cohorts is needed to validate these findings as well as exploring possible alternatives.
GENUS: Research on sensory stimulation to combat Alzheimer's disease
References
Further Reading
The association between handgrip strength and dementia risk in a UK population of middle-aged adults