Difficulty in falling asleep doubles risk of depression in older men, conclude researchers at the Western Australian Centre for Health and Ageing at The University of Western Australia.
A Swiss study found a few years ago that persistent insomnia could increase the risk of depression in young adults.
But then sleep complaints are common in later life, with nearly 50 per cent of people older than 65 years reporting trouble falling or remaining asleep.
"We found a strong link between difficulty falling asleep and depression which cannot be explained adequately by reverse causality that is, that depression causes insomnia. We didn't expect to find this result, so it took us by surprise," said UWA Chair of Geriatric Psychiatry and Director of Research at the Western Australian Centre for Health and Ageing, Winthrop Professor Osvaldo Almeida.
"Excuse the pun, but our results are a wakeup call. I believe that clarifying what drives the association between sleep problems and depression should become an international research priority. Worryingly, our results are consistent with the possibility that the use of sleeping tablets is actually driving this increase in the risk of depression. Addressing this issue may guide the development of prevention strategies to decrease the burden of depression in our society.
"Depression is the leading cause of disability worldwide and affects between 5 and 15 per cent of adults over 65. People need to be aware that depression is not a normal part of ageing.
"Sleep is just as important to our physical and emotional health in our senior years as it was when we were younger. Nevertheless, some changes in your sleep are natural as you age."
The study found that of the 5,127 men taking part, 60 per cent complained of poor sleep. Eighteen per cent of these reported difficulty in falling asleep, 10 per cent remained awake and 72 per cent reported early morning awakening.
To promote good sleep, Professor Almeida suggests older men should pay particular attention to their pre-bedtime diet. "If you are an older man, minimise liquid intake before sleep: avoid coffee, tea, soft drinks and chocolate late in the day. Don't use alcohol as a sleeping aid. Exercise regularly. Make your bedroom quiet and dark and avoid watching TV in bed. If possible, keep a regular bedtime routine. And steer clear of taking sleeping pills for long periods of time."
This research was part of the Health In Men Study (HIMS) that has been following a group of men living in Perth, Western Australia since 1996. HIMS is the largest study of ageing men in Australia. The men were originally recruited for a trial of screening for abdominal aortic aneurysm.
For the sleep research study, participants were randomly selected from the electoral roll. Between 1996 and 1999, 12,203 of the men aged 65 years and older attended a clinic and completed a questionnaire, providing a range of demographic and risk factor data. Approximately five years later, 10,940 surviving men were invited to a follow-up study. Between 2001 and 2004, 5,585 men completed a second questionnaire, and 4,263 of these attended a clinic.
"The study included only men," Professor Almeida said, "though it is very likely that women will experience the same sleep disturbances, however further studies will be needed to confirm this."
The new study is published in this month's edition of Journal of Affective Disorders