The beneficial effects of bright-light therapy in certain patients with Parkinson's disease appear to be confirmed by a systematic review and meta-analysis of small randomized controlled trials, according to researchers in China. As Dr. Guoen Cai told Reuters Health by email, "Bright-light therapy improves depressive symptoms and sleep disturbance in patients with Parkinson's disease." However, he added, establishing the "appropriate therapeutic parameters" requires more work. In a paper in Sleep Medicine, Dr. Cai of Fujian Medical University and colleagues note that characteristic non-motor symptoms of the disease include sleep disturbances and depression. And medication for Parkinson's disease is known to prompt sleep disturbances and this in turn is often accompanied by depression. In addition, medications for treating these symptoms have their own side effects. Hypnotics, for example, may increase sedation during the day and make falling more likely. Antidepressants can cause orthostatic hypotension and cognitive dysfunction and potentially worsen motor symptoms. Bright-light therapy (BLT) has been shown to be effective in treatment of sleep and circadian disturbances in patients with Alzheimer's disease and has proved beneficial in treatment of depression. To gauge how effective it might be in Parkinson's patients, the researchers searched the literature and identified five clinical trials involving 173 such patients. These compared the effect of control lighting and BLT. Most of the studies used light intensity of 1,000 to 7,500 lux administered in bursts of one to two hours. A meta-analysis involving 145 patients showed that in the control group, no difference in degree of depression was observed after exposure. However, the depression score of patients after BLT was significantly lower than that before BLT. A further analysis involving 42 patients in whom insomnia data were accessible showed that the insomnia score after BLT was significantly lower than that before BLT. There was no difference in the control group. The researchers note that all adverse effects appeared to be mild and transient and conclude that "BLT seems to be well-tolerated, easy to use, and is an inexpensive non-pharmacological treatment option." Dr. Claire Henchcliffe, chair of neurology at the University of California, Irvine, told Reuters Health that the outcome "is great news for people with Parkinson's disease (PD), in whom both sleep and mood disturbances are extremely common. The results are complicated by finding a smaller trend for benefit from control light, as well as the relatively small number of patients included in heterogeneous studies. Nonetheless, there is a great deal of enthusiasm for effective alternatives to pharmacologic therapies." Dr. Henchcliffe, who was not involved in the research, added, "This study supports the need for interventional clinical trials as rigorous tests of what benefits bright light therapy is able to provide." "One such study," she added, "named ENLITE PD has recently launched through the NeuroNEXT clinical trials network. Led by Dr. Alexander Videnovic of Massachusetts General Hospital, this extremely innovative NIH-funded study will rigorously test how different doses of light exposure will perform as a potential treatment for sleep in PD." ENLITE PD details are available at https://bit.ly/3aqCOpw. The work did not have any commercial funding, and the researchers report no conflicts of interest. —David Douglas Source
