A study of German university students found that they tended to delay their bedtime on days when they experienced higher levels of stress. Their sleep quality also declined during these periods. The research was published in Stress and Health.
Sleep is essential for maintaining overall health, as it allows the body and brain to rest, recover, and perform critical functions like memory consolidation, hormone regulation, and tissue repair. During sleep, the brain processes information from the day, which strengthens learning and supports cognitive functions such as problem-solving and decision-making. Adequate sleep is also crucial for emotional regulation, as it helps manage stress and promotes mood stability.
In contrast, insufficient sleep negatively affects cognitive performance, leading to issues such as impaired concentration, slower reaction times, and poor judgment. Chronic sleep deprivation can weaken immune function, making the body more susceptible to infections and illnesses. It also disrupts metabolic processes, increasing the risk of weight gain, diabetes, and cardiovascular diseases. A lack of sleep raises stress hormone levels, contributing to high blood pressure and heart problems. Over time, consistent sleep deprivation has been linked to an increased risk of chronic health conditions and an overall decline in quality of life.
Study author Laura I. Schmidt and her colleagues aimed to examine how daily stress contributes to sleep quality and bedtime procrastination. Bedtime procrastination occurs when a person delays going to bed as planned without any external reasons for doing so (i.e., without anything preventing them from going to bed on time). The researchers hypothesized that high daily stress might contribute to bedtime procrastination, as well as to shorter and poorer quality sleep.
They conducted a daily diary study with 96 students from Heidelberg University in Germany, recruited through online psychology student groups. Participants received course credit for their participation. Eighty-four percent of the participants were female, and their average age was 22 years.
Over the course of 14 days, participants wore an actigraphy device (the Fitbit Charge HR) that monitored their movements to record their total sleep duration and timing. Participants also completed subjective assessments of sleep quality (the Pittsburgh Sleep Diary), daily stress (the Heidelberger Stress-Index), and answered questions about engagement in unplanned but controllable late-night activities, as well as their intended time to go to sleep. The researchers calculated bedtime procrastination as the difference between the time participants reported planning to go to sleep and the time the actigraphy device registered them falling asleep.
On average, participants delayed their sleep time by 15 minutes and postponed their bedtime on 15% of the study days. When they postponed their bedtime, it was by an average of 102 minutes. Participants slept an average of 7.5 hours per night.
On nights when participants delayed their bedtime, their sleep duration was typically shorter, and their sleep quality tended to be worse. Higher symptoms of smartphone addiction were slightly associated with postponing bedtime. Some participants had a habit of delaying their sleep time, while others tended to go to bed on time. Participants were more likely to postpone their bedtime on days when they experienced higher levels of stress.
The study authors tested a statistical model proposing that bedtime procrastination mediates the link between daily stress and sleep duration/quality. The results suggested that this relationship is indeed plausible.
“Results of our study indicate that higher stress contributes to higher BP [bedtime procrastination] and additionally to decreases in sleep duration and quality. Daily BP was a mediating factor of the relationship between stress and sleep outcomes,” the study authors concluded.
The study sheds light on the links between stress and sleep quality. However, it should be noted that the study was conducted on psychology students. Results on other age and demographic groups might not be the same.
The paper, “Postponing sleep after a stressful day: Patterns of stress, bedtime procrastination, and sleep outcomes in a daily diary approach,” was authored by Laura I. Schmidt, Anke S. Baetzner, Marina I. Dreisbusch, Alica Mertens, and Monika Sieverding.
