It may be “one of the most promising interventions for improving core symptoms” of the disease.
A new meta-analysis shows that patients with dementia who received phototherapy experienced significant cognitive improvement, compared with those who received usual treatment. However, there were no differences between study groups in terms of improved depression, agitation, or sleep problems.
“Our meta-analysis indicates that phototherapy improved cognitive function in patients with dementia. ... This suggests that phototherapy may be one of the most promising non-pharmacological interventions for improving core symptoms of dementia,” wrote the investigators, led by Xinlian Lu, Peking University, Beijing.
The study was published online in Brain and Behavior.
A new treatment option?
“As drug treatment for dementia has limitations such as medical contraindications, limited efficacy, and adverse effects, nonpharmacological therapy has been increasingly regarded as a critical part of comprehensive dementia care,” the investigators noted.
Phototherapy, which utilizes full-spectrum bright light (usually > 600 lux) or wavelength-specific light (for example, blue-enriched or blue-green), is a “promising nonpharmacological therapy” that is noninvasive, inexpensive, and safe.
Most studies of phototherapy have focused on sleep. Findings have shown “high heterogeneity” among the interventions and the populations in the studies, and results have been “inconsistent.” In addition, the effect of phototherapy on cognitive function and behavioral and psychological symptoms of dementia (BPSD) “still need to be clarified.”
In the systematic review and meta-analysis, the investigators examined the effects of phototherapy on cognitive function, BPSD, and sleep in older adults with dementia.
They searched several databases for randomized controlled trials that investigated phototherapy interventions for elderly patients. The primary outcome was cognitive function, which was assessed via the Mini-Mental State Examination (MMSE).
Secondary outcomes included BPSD, including agitation, anxiety, irritability, depression, anxiety, and sleep disturbances, as assessed by the Cornell Scale for Depression in Dementia (CSDD), the Cohen-Mansfield Agitation Inventory (CMAI), the Neuropsychiatric Inventory (NPI), and measures of sleep, including total sleep time (TST), sleep efficiency (SE), and sleep disorders, as assessed by the Sleep Disorder Inventory (SDI).
To be included in the analysis, individual studies had to focus on elderly adults who had some form of dementia. In addition, a group receiving a phototherapy intervention had to be compared with a nonintervention group, and the study had to specify one of the above-defined outcomes.
The review included phototherapy interventions of all forms, frequencies, and durations, including use of bright light, LED light, and blue or blue-green light.
Regulating circadian rhythm
Twelve studies met the researchers’ criteria. They included a total of 766 patients with dementia – 426 in the intervention group and 340 in the control group. The mean ages ranged from 73.73 to 85.9 years, and there was a greater number of female than male participants.
Of the studies, seven employed routine daily light in the control group, while the others used either dim light (≤ 50 lux) or devices without light.
The researchers found “significant positive intervention effects” for global cognitive function. Improvements in postintervention MMSE scores differed significantly between the experimental groups and control groups (mean difference, 2.68; 95% confidence interval, 1.38-3.98; I2 = 0%).
No significant differences were found in the effects of intervention on depression symptoms, as evidenced in CSDD scores (MD, −0.70; 95% CI, −3.10 to 1.70; I2 = 81%).
Among patients with higher CMAI scores, which indicate more severe agitation behaviors, there was a “trend of decreasing CMAI scores” after phototherapy (MD, −3.12; 95% CI, −8.05 to 1.82; I2 = 0%). No significant difference in NPI scores was observed between the two groups.
Similarly, no significant difference was found between the two groups in TST, SE, or SDI scores.
Adverse effects were infrequent and were not severe. Two of the 426 patients in the intervention group experienced mild ocular irritation, and one experienced slight transient redness of the forehead.
Light “may compensate for the reduction in the visual sensory input of patients with dementia and stimulate specific neurons in the suprachiasmatic nucleus of the hypothalamus to regulate circadian rhythm,” the researchers suggested.
“As circadian rhythms are involved in optimal brain function, light supplementation may act on the synchronizing/phase-shifting effects of circadian rhythms to improve cognitive function,” they added.
They note that the light box is the “most commonly used device in phototherapy.” Light boxes provide full-spectrum bright light, usually greater than 2,500 lux. The duration is 30 minutes in the daytime, and treatment lasts 4-8 weeks.
The investigators cautioned that the light box should be placed 60 cm away from the patient or above the patient’s eye level. They said that a ceiling-mounted light is a “good choice” for providing whole-day phototherapy, since such lights do not interfere with the patient’s daily routine, reduce the demand on staff, and contribute to better adherence.
Phototherapy helmets and glasses are also available. These portable devices “allow for better control of light intensity and are ergonomic without interfering with patients’ normal activities.”
The researchers noted that “further well-designed studies are needed to explore the most effective clinical implementation conditions, including device type, duration, frequency, and time.”