As you can read in our overview, researchers have found solid theoretical reasons to expect phototherapy to provide relief from some symptoms of Alzheimer’s disease. However, reality is quite confusing. Some studies are showing that phototherapy does help while others show that it does not. I would be totally confused myself if not for the careful systematic review of all available research provided by Italian scientists in 2018.
What are the results?
First of all, the doctors examined all available literature and chose 32 studies scrutinizing the effect of bright light therapy on sleep, mood, and cognition in Alzheimer’s patients. Second, they evaluated their quality. Finally, they reported the final results for sleep, mood, and cognition.
Does light improve sleep in Alzheimer’s patients?
It appears so. Although not all the studies confirmed the effects, it seems that the unsuccessful were either using a weak light (300 lux compared to 10,000 we use normally) or they studied patients over 80 years old in a very severe phase of the disease who were too far gone to respond to the treatment.
Conclusion: available data shows a positive trend. We need to investigate the matter further to discover the ultimate proof.
Does light improve Alzheimer’s patients’ cognition?
Only 5 studies looked at this question but all of them answered that phototherapy works. Again, this is not undeniable proof and we need more research. However, the probability of the lamps having at least some effect on Alzheimer’s patients is optimistic.
Does light improve Alzheimer’s patients’ mood and behaviour?
We have 19 studies with mixed results on this topic. Overall, there were suggestions of positive effects particularly on depression. Again, this is more likely to appear in patients with mild to moderate dementia than in those with severe Alzheimer’s. However, two studies also reported worsening of symptoms in some patients. Verdict: promising but more detailed research needed.
Phototherapy had a greater impact during winter than during summer. Such a difference indicates that it really was the light therapy and not placebo treatments that improved symptoms of the disease. On the other hand, in some studies, there were nurses ensuring that the patients were actually sitting in front of their light boxes during treatment, As a result, sometimes it might have been the human interaction rather than the light therapy which had an impact. Altogether: light indeed seems to help with Alzheimer’s, but we need much more research to confirm how, when, and to what effect.
Whom and how to treat?
Naturally, patients with less severe disease benefit more from the treatment. The effect is stronger in the winter. High-intensity, perhaps blue-enriched light might be appropriate to compensate for the loss of melanopsin cells due to Alzheimer’s.
“Overall, the current literature suggests that the effects of light treatment in AD patients are mixed and may be influenced by several factors, but with a general trend toward a positive effect. Bright light seems to be a promising intervention treatment without significant adverse effects; therefore, further well-designed randomized controlled trials are needed taking into account the highlighted recommendations.”Mitolo, Tonon, La Morgia, Testa, Carelli, Lodi (2018). Effects of Light Treatment on Sleep, Cognition, Mood, and Behavior in Alzheimer’s Disease: A Systematic Review. Dement Geriatr Cogn Disord 2018; 46:371–384.