Effects Of Red Light On Sleep And Mood In Normal Subjects And Patients With Insomnia Disorder

ObjectiveTo study the changes of sleep and mood in patients with insomnia disorder and normal subjects after receiving red light irradiation before going to bed,and to explore the influence of red light on sleep and the relationship between mood and sleep.MethodsAccording to the diagnostic criteria of insomnia disorder in the American Diagnostic and Statistical Manual of Mental Disorders,a total of 57 patients with insomnia disorder and 57 normal subjects were recruited.Subjects in these two groups were randomly divided into three groups(red light group,white light group,and black control group)and received corresponding light treatment for 1 hour before going to bed.Emotion assessment scales and alertness assessment scale were used to evaluate the subjects’ emotions and subjective alertness,and the sleep data of the subjects were recorded by polysomnography.SPSS 26.0was used to analyze the recorded data.Results1.The negative emotional score of NS-RL group was higher than that of NS-WL group and NS-BC group(P=0.000).The anxiety score and negative emotion score in ID-RL group were higher than those in ID-WL group and ID-BC group(P= 0.007;P = 0.000).Compared with the NS-RL group,anxiety scores increased more in the ID-RL group after receiving red light irradiation,and there were more negative emotion items with differences in the Positive and Negative Affect Scale.2.The Karolinska Sleep Scale scores in the RL group was lower than those in the WL group and the BC group in both the NS group and the ID group(P=0.000;P=0.000).3.The sleep onset latency of NS-RL group was shorter than that of NS-WL group(P=0.019).Compared with NS-BC group,NS-RL group showed an increase in microarousal index and the percentage of N1 sleep(P=0.034;P=0.021),while the total sleep time and sleep efficiency decreased(P=0.001;P=0.000).Compared with ID-WL group,the sleep onset latency of ID-RL group was shortened(P=0.043),while the total sleep time,sleep efficiency,the number of cycles and microarousal of REM sleep were increased(P=0.016;P=0.046;P=0.001;P=0.041).Compared with ID-BC group,IDRL group showed an increase in sleep onset latency,wakefulness time after sleep,number of cycles of REM sleep and number of microarousal(P=0.038;P=0.005;P=0.045;P=0.033),and a decrease in sleep efficiency(P=0.014).4.Sleep onset latency and wakefulness time after sleep were positively correlated with anxiety score,depression score and negative emotion score,sleep efficiency was negatively correlated with anxiety score and depression score,and the number and index of REM sleep microarousal were positively correlated with anxiety score and negative emotion score.5.The effects of ID-WL group(vs.ID-RL group)and ID-BC group(vs.ID-RL group)on sleep latency were mediated by negative emotions(mediating effects were-37.626 and-33.768).Conclusion1.Red light can increase subjects’ subjective alertness,anxiety level and negative emotion level,but the degree of its influence on emotion is different between the normal subject group and the insomnia disorder group.The mood of insomnia patients is unstable,and the anxiety level and negative emotion level of insomnia patients increase more when exposed to red light.2.Compared with black control group,red light still affected sleep to some extent,but the effect is weaker than that of white light with the same illuminance.Red light may be more beneficial to sleep if you are exposed to white or red light of the same illumination before bed.3.In this study,red light,white light and darkness not only have direct effects on sleep,but also have indirect effects on sleep through negative emotions,which play a partial intermediary role between light and sleep.