Abstract
BACKGROUND: Patients with myocardial infarction (MI) can have disturbed sleep, but little is known about the efficacy of light therapy on sleep and the prognosis of patients with MI. We conducted a randomized controlled study to investigate its efficacy. MATERIAL AND METHODS: This preliminary study included 34 patients with MI. They were randomized into the blue light and the white light groups during their stay in intensive care unit. 17 age and gender-matched healthy controls were also enrolled. Actigraphy was used to evaluate objective sleep since enrollment. Delirium scales were used to screen delirium. Lab work-up, including vitamin D level was performed at the baseline and discharge. We used the Mann-Whitney U test or Wilcoxon signed-rank test to compare the difference between the MI group and the healthy control group, and the group difference after receiving light therapy. RESULTS: Patients with MI had significantly lower vitamin D levels than healthy controls (p < 0.001). They also had significantly poorer sleep, as indicated by actigraphy parameters, including sleep onset latency (p = 0.01), sleep efficiency (p = 0.002), wake after sleep onset (p < 0.001), and awake times (p = 0.002). No significant group difference was found by actigraphy after light therapy except a non-significant higher relative amplitude of the blue light group (p = 0.061). Besides, the vitamin D level of the blue light group increased significantly (p1 = 0.047, p2 = 0.045). CONCLUSIONS: Patients with MI had poorer sleep, highlighting the need to develop interventions. Significantly increased vitamin D levels and a non-significant better rest-active rhythm after light therapy suggest its potential with sleep and prognosis, which warrants further investigation.