A study by Brandeis researchers showing a link between light exercise and better sleep was published in last month’s issue of “Sleep Journal,” which is published by the National Sleep Foundation. The study, “Walk to a better night of sleep: testing the relationship between physical activity and sleep,” found that participants who were more physically active had better sleep quality, but not more sleep overall. 

The study was written and conducted by Alycia Sullivan Bisson MA ’17 PhD ’20, Stephanie Robinson PhD ’18 and Margie Lachman PhD. Fifty-nine Boston-area residents with an average age of 49.43 participated, according to the study. Each participant tracked their physical activity using FitBit Zips for four weeks, and according to a Nov. 1 New York Times article, reported their sleep duration and quality in questionnaires each day, as well as at the beginning and end of the four-week period. 

In a joint Nov. 8 interview with Bisson and Lachman, Bisson told the Justice that participants were told to rate their sleep quality each day on a scale from zero to 10. Although Bisson said that they did not give participants criteria defining good or poor sleep quality, the New York Times article explained that sleep quality could include factors such as “how long it took them to fall asleep, how often they woke up, or how refreshed they felt the next morning.” 

The researchers also found that the relationship between physical activity and sleep was related to each person’s sex. “Sex moderated this relationship; women who took more steps and were more active reported sleeping better than those less active,” the study said. Women who were more active over the course of the month said they slept better, whereas men who were more active did not. 

Men and women, however, reported better sleep quality and duration “on days that participants were more active than average.” Regardless of sex, a person who was more active than usual on any day would report better sleep that night. 

Bisson emphasized that it was important to note that both sleep quality and duration were self-reported, and that people’s views of their own sleep are not objective. “We’re not entirely sure how people’s views of their own sleep match up to how well they actually sleep, so that’s something we’re doing in future studies,” Bisson said. She specified that because of the self-reporting, they found that physical activity “changed how well they felt that they slept,” not how well they had actually slept.

By studying adults who did not suffer from sleep disorders and focusing on mild exercise, this study filled a gap in sleep research. Many previous studies on the relationship between sleep and physical activity have focused on subjects who were younger, had sleep problems or engaged in high-impact exercise, per a Nov. 7 Boston Globe article. According to the study, the researchers wanted to focus on “whether low-impact daily PA [physical activity], like walking, can affect sleep in healthy adults.” This way, they were able to find that “just walking is enough to make a difference,” Bisson said. 

Lachman and Bisson said during the same interview that there are other areas in the field that still need further research. Lachman said she was curious about why physical activity improved sleep. Lachman also emphasized that their research found a correlative relationship between physical activity and sleep, not a causal relationship, and that further research would have to be done to prove any type of causation. Bisson added that there were other possible relationships between physical activity and sleep, such as that well-rested people have energy to be more active, or that healthy people tend to exercise and sleep more than others. Proving or disproving these hypotheses would involve further research, Bisson said. 

Both researchers said that research on physical activity, including theirs and others’, led them to be more physically active in their own lives. Bisson said during the same interview that she had a “walking buddy” at work. “I definitely try to practice what I preach,” Lachman added. Lachman explained that in addition to their study, there is a wealth of research showing the physiological benefits of exercise, so she tries to stay physically active. “You can’t go wrong by doing more exercise,” she said.