Does walking outside during the day help me sleep better at night?

Walking outside for 35 minutes a day measurably improves sleep quality. A randomised study of 104 students with sleep problems showed this: after seven days their sleep had improved significantly, whether they walked through a park or through the city. Nature itself made no difference; what mattered was moving around outdoors.

A smaller pilot study of fourteen inactive adults who went outside to exercise at least three times a week for eight weeks also found an increase in the proportion of good sleepers, from 50% to 64%. This difference was not statistically significant, however, most likely because the study was simply too small to demonstrate anything with certainty.

People who regularly use walking trails also report better sleep than people who do not. But this type of comparison shows only an association, not a cause. It is equally possible that people who already sleep well simply go outside more often.

There is one caveat when it comes to walking outside in busy or polluted areas. Research covering 58 studies shows that higher air pollution is associated with poorer sleep quality and shorter sleep duration. If you live or walk in an environment with heavy traffic or industry, this benefit may be partly cancelled out.

For cancer patients the picture is currently too unclear to say anything about the effect of outdoor exercise on sleep; that research has provided too little solid ground.