Sleep disturbance, especially insomnia, is a common complication after ischemic stroke for the patients during rehabilitation of cerebral infarction. Actually, more than half of ischemic stroke patients have insomnia complaints. Meanwhile, poor quality of sleep may greatly impede stroke rehabilitation and induce other complications. Thus, it is of importance to study the insomnia for the post-stroke patients, especially when they are during rehabilitation of cerebral infarction.

Melatonin is a pineal hormone with the peak nocturnal secretion. Melatonin typically takes a large responsibility in coordination with the circadian rhythms and further serves as a regulator in the sleep function. The secretion peak of melatonin is around midnight to 3:00 a.m.. Along with other antioxidants, the melatonin can also work as an effective neuroprotective enzyme against neurodegeneration and ischemic brain injury. Thus, the melatonin is known to take an important role in acute ischemic stroke, with a rhythm impairment and nocturnal decrease. γ-Aminobutyricacid (GABA) is likewise a strong sleep regulator that may activate GABA receptors as well as inhibitors of waking processes. It is known that GABA level in the human body is strongly associated with the impairment of patients in the acute ischemic stroke. Antioxidant may take a critical role in the balance of oxidation by scavenging free radicals, so it is regarded as an important marker in studying the insomnia for the post-stroke patients. However, to our knowledge, there is almost no report on simultaneous measurements of levels of melatonin, GABA and antioxidants in the bloods of patients during the convalescence of ischemic stroke or on studying their association with the insomnia complication for the post-stroke patients.

Therefore, this prospective single-center randomized controlled clinical trial was designed to investigate the relationship of nocturnal concentrations of melatonin, γ-aminobutyric acid and total antioxidants with insomnia after stroke by comparing the nocturnal concentrations of melatonin, GABA and total antioxidants in stroke patients with insomnia or without insomnia and normal controls.

Data management Clinical researchers accurately, completely, timely filled out the clinical trial observation form. Data were recorded electronically by data managers using a double-data entry strategy. The electronic database was locked by the project manager after checking. All data were analyzed statistically by professional statisticians. Anonymized trial data will be published at www.figshare.com.

Statistical analysis Data were presented as the mean ± standard deviation for normally distributed variables, or median values (P25, P75) for non-normally distributed variables. Student's t-tests or nonparametric Mann-Whitney tests were performed to compare the differences between normally distributed variables or non-normally distributed variables. For the analysis of biochemical test results, data were transferred to normal distribution and Hotelling's T2 tests were performed. Before entering variables into the regression model, centering predictor variables were performed to avoid nonessential collinearity. Binary logistic regression analysis was conducted to identify the association between variables or variables interaction and insomnia diagnosis after infarction. Multiple linear regression analysis was carried out to determine the correlation between variables or variables interaction and sleep-related scores, such as Epworth Sleepiness Scale scores, Pittsburgh Sleep Quality Index scores, Insomnia Severity Index scores, Morningness-Eveningness Questionnaire (Chinese version) scores and Fatigue Severity Scale scores by using backward method. P values \< 0.05 were considered statistically significant. SPSS 22.0 software was used for statistical analysis.