More activity outside during the day means less sleep disruption at night.
Lack of sleep can have a wide range of negative effects on both physical and mental health. Key consequences of poor sleep include a reduce ability to fight off infections and illnesses, higher likelihood of developing heart disease, diabetes, and hypertension, difficulties with attention and concentration, and memory issues (the list goes on and on).
How to ensure adequate sleep for your overall health? Be a gardener!
The nationwide study included more than 60,000 participants and showed that those who gardened regularly had "lower odds of multiple sleep complaints" (i.e. sleep apnea and insomnia).
Other studies have shown that gardening may even improve dementia symptoms. This article from Real Simple details the benefits of spending time in outside, just being in nature (even if you don't garden).