The millions of middle-aged and older adults who suffer from insomnia have a new drug-free prescription for a more restful night's sleep. Regular aerobic exercise improves the quality of sleep, mood and vitality.

The small but significant study from Chicago-based Northwestern Medicine looked at sedentary adults, who had difficulty falling asleep or staying asleep. Most were women aged 55 and older.

One group exercised for forty minutes four times per week, for 16 weeks.

The other group took part in recreational and educational activities for 45 minutes three to five times per week for the same period.

Both groups received education about good sleep practices, which include sleeping in a cool, dark and quiet room; going to bed the same time every night; and not staying in bed too long, if you can't fall asleep.

But it was the exercise group that emerged with better sleep quality. They also reported fewer depressive symptoms, more vitality and less daytime sleepiness.

Bottom line: We know exercise is good for metabolism, weight management and cardiovascular health. Now it's good for sleep.