The Munich Chronotype Questionnaire (MCTQ) has been widely validated among various types of populations. However, determination of chronotype among individuals who have a split sleep pattern with short intervals between the first and second sleep bouts on free days has not yet been reported. This study aimed to validate the MCTQ modified for this purpose by assessing the actual sleep-wake timing against the Morningness-Eveningness Questionnaire (MEQ). The modified calculation for the midpoint of sleep on free days (MSF) of the split sleep pattern considers the second sleep bout as the total sleep duration on free days. We recruited 161 participants (mean age: 38.7 ± 7.8 years; 73% females, 29% with split sleep pattern) were recruited to administer the modified version of the MCTQ and MEQ. All of the MCTQ original parameters: midpoint of sleep on work days (MSW, r = -0.575), midpoint of sleep on free days (MSF, r = -0.568), and midpoint of sleep on free days corrected for sleep debt (MSFsc,r = -0.566) were significantly correlated with MEQ. The MEQ was further tested against MSF in four conditions of the split sleep pattern. The MSF modified for split sleep within 60 minutes after the first awakening showed highest correlation (r = -0.576) against MEQ score. The results demonstrate the modified version of MCTQ is valid to determine the chronotype in participants who practice consolidated and split sleep patterns.
Background: The effect of circadian disruption on the bio-psychological clock system has been widely studied. However, the mechanism and the association of circadian rhythm disruption with mental health and physiological responses are still unclear. Therefore, this study was conducted to investigate the effects of circadian rhythm disruption on mental health and physiological responses among shift workers and the general population. Methods: A total of 42 subjects participated in this quasi-experimental study. Participants were divided into a group of shift workers (n = 20) and a general population group (n = 22). Polysomnography tests, blood tests (cortisol, triglycerides and glucose), and psychological tests (Abbreviated Profile of Mood States, General Health Questionnaire-28, Working Memory and Processing Speed Indexes of the Wechsler Adult Intelligent Scale (WAIS-IV) were used to examine the effects of circadian rhythm disruption. Results: The results showed a significant relationship between circadian rhythm disruption and mood (r = 0.305, p < 0.05). The findings of this study also indicated that there was a significant effect of circadian rhythm disruption on mood (F(2,40) = 8.89, p < 0.001, η2 =0.182), processing speed (F(2,40) = 9.17, p < 0.001, η2 = 0.186) and working memory (F(2,40) = 4.963, p < 0.01, η2 = 0.11) in shift workers and the general population. Conclusions: Our findings showed that circadian rhythm disruption affects mood and cognitive performance, but it does not significantly affect psychological wellbeing and physiological responses. Future studies are warranted to examine moderator and mediator variables that could influence the circadian rhythm disruption.