Bright Light Therapy for Parkinson Disease: A Literature Review and Meta-Analysis of Randomized Controlled Trials

Abstract

Sleep disorders and depression are significant nonmotor symptoms (NMSs) of Parkinson disease (PD). However, few effective, evidence-proven medical treatments are available for alleviating these symptoms. Bright light therapy (BLT) is a well-established treatment for circadian rhythm sleep disorders and seasonal affective disorder. The present study conducted a literature review for the effect of BLT on PD, especially a meta-analysis of randomized controlled trials (RCTs). We searched for studies using the PubMed and Cochrane Library databases. The major outcomes were the effects on sleep and depression. The effect on motor symptoms was also analyzed as a secondary outcome. This study was registered with PROSPERO (CRD42020204454). Six studies were included in the literature review only, and the other five RCTs were included in the meta-analysis. Despite the positive effects of BLT on PD patients, which were demonstrated in noncontrolled studies, in the meta-analysis of the RCTs, BLT did not significantly improve the depressive symptoms (standardized mean difference (SMD): −0.15, 95% confidence interval (CI): −0.48 to 0.17, p = 0.36) and excessive daytime sleepiness (EDS) (SMD: −0.12, 95% CI: −0.49 to 0.25, p = 0.53) in PD patients. Regarding motor symptoms, no significant beneficial effects were conferred (SMD: −0.11, 95% CI: −0.44 to 0.21, p = 0.49). In conclusion, BLT did not significantly alleviate depression and sleepiness. The inconsistency between BLT protocols, such as the varied timing, dosages, and treatment durations, may render BLT’s efficacy difficult to demonstrate. The small effect size obtained from the present meta-analysis indicates that future RCTs are necessary, for which BLT protocols are standardized and more patients are enrolled to determine whether a significant therapeutic benefit was conferred.

Efficacy of non-pharmacological interventions for depression in individuals with Parkinson's disease: A systematic review and network meta-analysis

“…Therefore, related results should be interpreted with caution. Conventional meta-analyses, including RCTs, showed that yoga, BLT, rTMS, and psychotherapy significantly improved depression (Ban et al, 2021;Chen et al, 2021;Hong et al, 2021;Huang et al, 2021); however, the evidence was relatively weak. Although a previous systematic review showed that physical exercise is beneficial for depression, it did not provide a quantitative analysis of the intervention effects (Cusso et al, 2016).…”

“…Owing to the limitations of pharmacological treatments, non-pharmacological treatments have been developed and have gradually gained popularity. Many non-pharmacological treatments have been used to relieve depressive symptoms in patients with PD, and these can be roughly categorized into complementary therapies (e.g., yoga, acupuncture, auricular pressure, massage, music therapy, and dance therapy), traditional Chinese exercises (e.g., tai chi and qigong), physical exercise (e.g., aerobic exercise, resistance exercise, and balance training), virtual reality, cognitive behavioral therapy (CBT), psychotherapy, cognitive training (CT), bright light therapy (BLT), deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), and transcranial direct current stimulation (tDCS) (Jin et al, 2019;Zhang et al, 2019;Deuel and Seeberger, 2020;Triegaardt et al, 2020;Chen et al, 2021;Hong et al, 2021;Huang et al, 2021). Previous studies (Troeung et al, 2014;Ryan et al, 2019;Assogna et al, 2020) have paid more attention to the effects of CBT and TMS on depression in PD patients and indicated that these two therapies are supportive for improving depression.…”

“…Previous systematic reviews have evaluated the effects of various non-pharmacological interventions on depression in individuals with PD (Cusso et al, 2016;Jin et al, 2019;Hai-Jiao et al, 2020;Triegaardt et al, 2020;Cartmill et al, 2021;Hong et al, 2021;Huang et al, 2021;Takamiya et al, 2021). However, some reviews included non-randomized controlled trials (RCTs) or lacked quantitative analyses (Cusso et al, 2016;Triegaardt et al, 2020;Cartmill et al, 2021;Takamiya et al, 2021); thus, these systematic reviews did not provide strong evidence.…”

Chronobiology of Parkinson's disease: Past, present and future

“…Indeed, evidence that such an effect arises from the amelioration of circadian dysfunction is supported by findings of rapid attenuation of oscillations in in vitro clock genes expression in mouse immortalized SCN neurons following chronic dopaminergic treatment (Endo et al, 2020). Further investigation of the potential of chronotherapy for the alleviation of disease‐and‐treatment‐related sleep and motor symptoms in PD is warranted as the current evidence base may be of sufficient quality to draw clinically useful conclusions (Huang et al, 2021).…”

“…The literature on circadian rhythms and PD, like in many adjacent areas, is currently dominated by relatively small studies with inconsistent protocols between studies (e.g., Huang et al, 2021). Multi-centred interdisciplinary work may address these concerns by enabling large-scale work, although of course funders will play a key role in enabling this.…”