Inflammation Equation

Older adults who sleep poorly have an altered immune system response to stress that may increase risk for mental and physical health problems. Kathi L. Heffner, from the University of Rochester Medical Center (New York, USA), and colleagues enrolled 45 women and 38 men, average age 61 years, in a study to assess the association between sleep disturbance, psychological stress, and inflammatory markers.  The participants were evaluated for cognitive status using a standard assessment. Each participant completed a self-report of sleep quality, perceived stress, loneliness and medication use. The participants had to be in good physical health to be in the study, but even so, about 27% of the participants were categorized as poor sleepers. On the day of the study, the participants were given a series of tests of verbal and working memory, a battery of questions that served as the stressor. Blood was drawn before any testing began and then immediately following the testing and at three intervals spaced out over 60 minutes. The blood was studied for levels of interleukin-6 (IL-6), a protein primarily produced at sites of inflammation. Poor sleepers reported more depressive symptoms, more loneliness and more global perceived stress relative to good sleepers. Poor sleepers did not differ from good sleepers when IL-6 was measured before the tests began. Across the group, the participants showed increases in IL-6. However, poor sleepers had a significantly larger increase in IL-6 in response to the stressful tests compared to good sleepers, as much as four times larger and at a level found to increase risk for illness and death in older adults. A further analysis of the results for the impact of loneliness, depression or perceived stress on IL-6 levels found no association. Poor sleep stood as the predictor of elevated inflammation levels.  Submitting that: "Findings add to the growing evidence for poor sleep as an independent risk factor for poor mental and physical health," the study authors conclude that: "Older adults may be particularly vulnerable to effects of sleep disturbance due to significant age-related changes in both sleep and inflammatory regulation.”