Discussion
sleep behavior, Health behaviors
DETACHMENT
Our randomized-controlled study did not support the effectiveness of an MCII intervention component over sleep hygiene information in a sample of early career researchers. Across all participants, results indicated an increase in sleep quality and subjective (but not objective) sleep duration from baseline to post-intervention period. Contrary to our preregistered hypotheses, there was no statistically meaningful group*week interaction for either sleep parameter indicating that the intervention group (MCII + SH) and the active control group (SH) did not differ in change in the sleep parameters from baseline to post-intervention week.Regarding daily stress, our hypothesis was partially confirmed, as significant associations of stress with all three sleep parameters on the between-person level were found: Participants with higher average stress slept shorter (objectively and subjectively) and reported lower sleep quality. On the within-person level, days with higher than usual stress were followed by nights with lower sleep quality, confirming the results of In line with the results on sleep outcomes, exploratory analyses regarding effects of the MCII intervention on the CAR did not show any significant effects. Thus, changes in the CAR from pre- to post-intervention were not different between study groups. Furthermore, overall changes in the CAR (across all participants) were not significant either.A possible explanation for the null-findings regarding the additional effectiveness of MCII on sleep outcomes is the short time-frame of the present study. For instance, Moreover, the suitability of MCII addressing sleep behavior needs to be discussed, as this study was the first to expand MCII on sleep research at the point of data collection. The approach to use MCII to improve sleep outcomes is based on the assumption that insufficient sleep results (at least partially) from self-regulatory failure. This assumption seems justified if sleep problems are due to factors implying a lack of self-control, such as “bedtime procrastination,” defined as going to bed later than intended without any legitimate reason and although negative consequences are expected (Aside from procrastination, it could be assumed that if sleep issues are due to other factors such as rumination or pre-sleep arousal, MCII might not be as effective. Health behaviors such as exercise or nutrition can be influenced more directly, whereas sleep outcomes are more difficult to change as they vary/differ in their degree of controllability. Trying harder is not necessarily the most successful approach when trying to fall asleep, and sleep problems cannot always be solved by exerting higher self-control. Another explanation for the null-finding might be a mediating role of energization regarding the MCII effect on goal commitment proposed by In addition to the short time frame, several limitations have to be considered. First, our design lacked a passive control group without intervention, making it impossible to attribute the positive overall increases to either sleep hygiene information (+MCII) or to the intensive self-monitoring with diaries and the Fitbit. Second, the study aim was rather obvious, which could have resulted in demand effects, which is supported by the fact that only self-reported measures, but not fitbit-measured sleep duration increased over the study period. However, also for fitbit-measured sleep duration, there was evidence for an abrupt increase from the night before to after the intervention. Third, our findings are based on a sample of university employees with relatively high degrees of flexibility in work schedules and findings may only be valid for populations with comparable job-related characteristics. Fourth, regarding CAR, we did not use objective methods to verify awakening or sampling times. Participants did not receive prompts to remind them of S2 or S3, but were instructed to set timers. Although participants received detailed information on the importance of adherence and although we applied strict accuracy margins in sensitivity analyses, this could have led to inaccurate CAR estimates. Furthermore, we were only able to assess the CAR on 2 consecutive days for each study period. Given the high variability of the CAR we therefore assessed important trait and state covariates to exclude CARs or control for them.Strengths of the present study include a strong active control condition, allowing detection of possible effects of MCII over a commonly used alternative (SH), a standardized intervention protocol allowing replication, a low dropout-rate, and the combined and intensive ambulatory assessment of daily self-report, CAR-assessment and fitbit-measured data. According to a meta-analysis (To conclude, our study did not find incremental effects of a MCII component over sleep hygiene (and self-monitoring) in a short time period as sleep quality and (subjective) sleep duration increased in both groups. The CAR did neither reveal changes nor differences between groups. Regarding subjective stress, associations with daily sleep parameters were largely confirmed. Future research should include booster sessions and evaluate MCII effects in the longer run. Additionally, the content of the implementations could be matched with a more diverse range of sleep-related outcomes. In our case, we learned from a workshop with 22 of our participants after data collection, that some participants perceived MCII as helpful to achieve their individual sleep-related goals (e.g. sleep onset latency, sleep schedule, sleep hygiene practice), but that this intervention effect was not reflected in our pre-defined outcomes sleep duration and quality.Aside from the need to disentangle effects of single behavior change components, a better understanding of the causes regarding insufficient sleep among specific target groups and their degree of controllability is required to develop individually targeted interventions. Additionally, moderators and mediators that have been recently linked to self-regulation, stress and sleep should be addressed, that is, detachment from work, rumination, or media/smartphone use (e.g. 