Regular aerobic exercise improves the quality of sleep, mood and vitality, according to a new study from Northwestern University, Chicago, US.

The study is the first to examine the effect of aerobic exercise on middle-aged and older adults with insomnia. About 50 per cent of people in these age groups complain of chronic insomnia symptoms.

The study included 23 sedentary adults aged 55 and older - primarily women, as they have the highest prevalence of insomnia -who had difficulty falling sleep and/or staying asleep and impaired daytime functioning.

After a conditioning period, the aerobic physical activity group exercised for two 20-minute sessions four times per week or one 30-to-40-minute session four times per week, both for 16 weeks. Participants worked at 75 per cent of their maximum heart rate on at least two activities including walking or using a stationary bicycle or treadmill.

Participants in the non-physical activity group participated in recreational or educational activities, such as a cooking class or a museum lecture, which met for about 45 minutes three to five times per week for 16 weeks.

Both groups received education about good 'sleep hygiene', which includes 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.

Exercise improved the participants' self-reported sleep quality, elevating them from a diagnosis of poor sleeper to good sleeper. They also reported fewer depressive symptoms, more vitality and less daytime sleepiness.

The research was funded by the National Institute on Aging.