Light Therapy Improves Sleep and Psychobehavioral Symptoms in Alzheimer Disease


Overall, the results revealed that light therapy helped to alleviate sleep efficiency, sleep quality, depressed mood, caregiver burden, and agitated behavior.

In a recently published meta-analysis of 15 randomized controlled trials (RCTs), results showed that light therapy has significant beneficial effects for patients with Alzheimer disease (AD), demonstrated by improvements in sleep and psychobehavioral symptoms.

Published in PLOS One, the analysis included studied with older adults (aged 60-85 years) diagnosed with AD and had Mini-Mental State Examination (MMSE) scores between 6 and 26. Patients in the intervention group had undergone light therapy, whereas those in the control group had received dim light or usual care. Four of the studies examined the application of light therapy devices while 11 involved light therapy. Two of the studies were cross-designed.

Senior author Qingui Meng, School of Nursing, Weifang Medical University, and colleagues assessed data of 598 patients with AD included in the studies, published between 2005 and 2022. Across 9 studies, sleep efficiency (SE), measured as total sleep time divided by the average time spent in bed, was more significantly improved through light therapy than usual care (mean difference [MD], –2.42; 95% CI, –3.37 to –1.48; I2 = 60%; P <.00001). On Pittsburgh Sleep Quality Index, light therapy continued to be more effective than usual care in improving sleep quality (MD, –1.73; 95% CI, –2.00 to –1.45; I2 = 0%; P <.00001).

Light therapy continued to perform well on the Neuropsychiatric Inventory (NPI), a validated assessment of behavioral and psychological symptoms of AD. Across 5 studies, light therapy outperformed usual care in reducing the severity of patients psychobehavioral symptoms (MD, –3.07; 95% CI, –4.14 to –2.00; P <.00001; I2 = 79%). The Zarit Caregiver Burden Interview (ZBI), a commonly used measure of adverse health outcomes, revealed that light therapy significantly reduced caregiver burden (MD, –3.57; 95% CI, –5.28 to –1.87; I2 = 0%; P <.00001).

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"These findings combined with its low side effects suggest the role of light therapy as a promising treatment for AD," Meng et al wrote. "Although light therapy has fewer side effects than pharmacological treatment, adverse behavioral outcomes in patients due to bright light exposure should be considered. Nevertheless, further studies with appropriately larger sample sizes are necessitated to elucidate the effectiveness of light therapy in treating sleep disorders and psychobehavioral symptoms in patients with AD."

In 3 studies, meta-analysis findings showed that light therapy could alleviate depressive symptoms in patients with AD, demonstrated by changes in Cornell Scale for Depression in Dementia (MD, –2.55; 95% CI, –2.98 to –2.12; I2 = 0%; P <.00001). Another 4 studies observed agitation through scores on the Cohen-Mansfield agitation inventory (CMAI). All told, light therapy proved to be relatively more beneficial than usual care for improving agitated behavior in patients with AD (MD, –3.97; 95% CI, –5.09 to 2.84; I2 = 0%; P <.00001). Of note, light therapy did not show a significant impact on cognition (MMSE MD, 0.44; 95% CI, –0.71 to 1.59; P = .45).

"Overall, our current systematic review suggested that light therapy is more effective than usual care. However, most included studies involve small sample sizes, while no agreement on light intensity and intervention duration currently exists," the study authors wrote. "Thus, the sample size of studies should be continually expanded and multicenter clinical studies are required to determine the optimal treatment modality that can be administered."

1. Zhang L, Liu X, Li Y, et al. The effect of light therapy on sleep disorders and psychobehavioral symptoms in patients with Alzheimer’s disease: a meta-analysis. PLOS One. Published online December 6, 2023. doi:10.1371/journal.pone.0293977
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