Light therapy leads to significant improvements in sleep and psycho-behavioural symptoms for people with Alzheimer’s disease, according to a new study.

The cognitive decline associated with Alzheimer's disease is often accompanied by sleep disturbances and psycho-behavioural symptoms including apathetic and depressive behaviour, agitation and aggression.

The study, published in the journal PLOS One, used photobiomodulation -- a non-pharmacological therapy that uses light energy to stimulate the suprachiasmatic nucleus (SCN) -- a sleep modulator in the brain.

The team from Weifang Medical University in China concluded that light therapy is a promising treatment option for some symptoms of Alzheimer's disease.

"Light therapy improves sleep and psycho-behavioural symptoms in patients with Alzheimer's disease and has relatively few side effects, suggesting that it may be a promising treatment option for patients with Alzheimer's disease," Qinghui Meng from the varsity said.

Despite light therapy receiving increased attention as a potential intervention for Alzheimer's, a systematic evaluation of its efficacy and safety has been unavailable.

To explore, researchers analysed 15 high-quality trials related to light therapy for Alzheimer's disease or dementia. The included trials were published between 2005 and 2022, performed in seven countries, and included a combined 598 patients.

The meta-analysis of all 15 trials found that light therapy significantly improved sleep efficiency, increased inter-daily stability (a measure of the strength of circadian rhythms), and reduced intradaily variability (a measure of how frequently someone transitions between rest and activity during the day).

In patients with Alzheimer's disease, light therapy also alleviated depression and reduced patient agitation and caregiver burden.

Given the limited sample sizes in studies included in this meta-analysis, the authors advocate for larger future studies, which could also explore if bright light exposure could cause any adverse behaviour in patients.