Insomnia and inflammation are risk factors for late-life depression. Both conditions are also highly prevalent in older adults. In the current study, researchers investigated whether inflammation increases depressive mood and symptoms in older adults with insomnia compared to those without the condition.
To do so, they conducted a randomized clinical trial including 160 adults aged 60 years or older without depression. A total of 53 individuals had insomnia and 107 did not. Participants were randomized into one of two conditions: receiving either a placebo or endotoxin- an 'inflammatory challenge' that is a reliable, safe and well-validated method of transiently inducing peripheral and central nervous system inflammation and increasing depressive symptoms in healthy adults.
Primary outcomes included self and observer-rated assessments of depressed mood completed at baseline, 30 minutes, and then hourly or every two hours. Phone interviews were conducted one and 7 days after the protocol to assess physical and depressive symptoms.
Ultimately, endotoxin induced significantly higher increases in depressed mood over 8.5 hours in those with insomnia than controls. In particular, the researchers noted that older adults with insomnia who were exposed to inflammatory challenge experienced a threefold greater increase in depressive mood and symptoms than healthy sleepers.
Further research is needed to know whether the findings apply to young populations with insomnia as well as more diverse ethnic demographics.
“Insomnia not only robs older adults of rest but also primes their immune system to make them uniquely vulnerable to depression when faced with inflammation,” lead author of the study, Michael Irwin M.D., Professor of Psychiatry and Biobehavioral Sciences at UCLA, said in a press release.
“Treatments targeted at this inflammation-related depression may prevent depression and benefit these patients to improve their overall quality of life,” he added.
Sources: EurekAlert, JAMA Psychiatry