The link between poor sleep and stress
By Liz Lockhart
Last week Mental Healthy reported on the links between stress and our immune system in the news article 
‘Depression hard-wired in the brain for survival’. New research now links an altered immune system response to older people who have a poor quality of sleep which may put them at an increased risk for poor mental and physical health.
The research has been conducted by the University of Rochester Medical Centre led by Kathi L. Heffner, Ph.D., assistant professor of Psychiatry at the Medical Centre. The study findings are published in the American Journal of Geriatric Psychiatry.
The research suggests that for poor sleepers, stress led to a significantly larger increase in a marker of inflammation when compared to good sleepers.
Heffner said ‘This study offers more evidence that better sleep not only can improve overall well-being but also may help prevent poor physiological and psychological outcomes associated with inflammation.’
Other factors such as immune impairment, including depression, perceived stress and loneliness could not account for the association between poor sleep and a heightened inflammatory response to acute stress.
‘Our study suggests that, for healthy people, it all comes down to sleep and what poor sleep may be doing to our physiological stress response, our fight-or-flight response,’ Heffner added.
There were 45 female and 38 male participants in the study, with an average age of 61. A standard assessment was used to evaluate the cognitive status of the participants and they each completed a self-report on factors such as perceived stress, loneliness, sleep quality and their use of medication. 27% of the participants were considered to be poor sleepers although they all had to be in good physical health to be accepted as participants on this study.
The participants underwent a blood test before they were given several tasks to test their verbal and working memory. These tasks were in the form of a battery of questions which were stressful. Blood tests were also conducted on three occasions during the tests and again at the end, over a period of one hour.
The blood samples were then studied by the researchers to find the levels of interleukin-6 (IL-6) which is a protein that is produced mainly in the areas of inflammation.
Compared to good sleepers, poor sleepers reported more symptoms of depression along with more loneliness and higher levels of perceived stress. The levels of IL-6 before the tests were started did not differ between the poor and the good sleepers. However, the participants demonstrated an increase in IL-6 in all participants throughout the tests, but the poor sleepers had a much larger increase in IL-6. The increase was as much as four times larger than that of good sleepers and this level is found to increase risk of illness and death in older people.
No association was found when a further analysis of the results for the impact of loneliness, depression or perceived stress on IL-6 was conducted, it was poor sleep alone that represented the predictor of elevated inflammation levels.
Heffner said ‘We found no evidence that poor sleep make them deal poorly with a stressful situation. They did just as well on the tests as the good sleepers. We did not expect that. We did find that they were in a worse mood after the stressor than a good sleeper, but that change in mood did not predict the heightened inflammatory response.’
It is usual that an increase in inflammation and a decline in the immune system occur as people get older. It is heightened inflammation which increases the risk of illness such as diabetes and cardiovascular disease along with psychiatric conditions.
Heffner concluded ‘There are a lot of sleep problems among older adults. Older adults do not have to sleep poorly. We can intervene on sleep problems in older adulthood. Helping an elderly person become a better sleeper may reduce the risk of poor outcomes associated with inflammation.’
