Vulnerability to Inflammation-Related Depression Exaggerated in Older Adults with Insomnia
Compared with older adults without insomnia, older adults with the sleep disorder experienced a 3-fold greater increase in depressed mood and depressive symptoms after exposure to an inflammatory challenge, according to study findings published in JAMA Psychiatry.
“Moreover, among those with insomnia, depressed mood persisted for more than 6 hours, with only transient increases in older adults without insomnia,” wrote corresponding author Michael R. Irwin, MD, of the Jane and Terry Semel Institute for Neuroscience and Human Behavior at the University of California, Los Angeles, and study coauthors.
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The randomized clinical trial included 160 community-based, nondepressed adults aged 60 years or older at a single site in Los Angeles, California, exposed to 1 of 2 conditions: administration of endotoxin to induce transient, robust peripheral and central nervous system inflammation or placebo. Among participants, 53 had insomnia disorder and 107 did not. Endotoxin was received by 26 participants with insomnia and 53 participants without insomnia.
In participants with and without insomnia, endotoxin induced similar increases in inflammatory cytokines, according to the study.
However, participants with insomnia who received endotoxin showed significantly greater and sustained increases in self-assessed depressed mood, as measured by the Profiles of Mood States depression subscale (POMS-D), compared with participants without insomnia. The effect was similar for observer-rated POMS-D assessment. Clinically meaningful increases in other observer-rated depression assessment scales (the Montgomery-Åsberg Depression Rating Scale and Hamilton Rating Scale for Depression) aligned with the findings.
Inflammatory response was associated with POMS-D increases in the insomnia group, moderation analyses indicated, but not in the control group.
“Most, if not all, studies examining depression responses to inflammatory challenge have enrolled healthy adults,” researchers wrote. “Here, this first-of-its-kind experimental study in older adults supports mechanistic links between insomnia, inflammation, and depression and provides novel scientific evidence that older adults with insomnia are uniquely vulnerable to depressive symptoms following inflammatory exposure.”
Therapies that target inflammation-related depression, they advised, may benefit older adults with insomnia.
