Locus Coeruleus Integrity in Older Adults with and without Chronic Pain

The locus coeruleus (LC) is a brainstem region involved in regulating pain. Chronic pain is common in older adulthood, but no studies have examined its association with the LC in humans. We used neuromelanin-sensitive imaging to study differences in LC integrity in older adults with and without chronic pain. Chronic pain was assessed in community-dwelling men from the Vietnam Era Twin Study of Aging (VETSA) in 3 study waves covering an average of 12 years. Pain was self-reported on the SF-36 Bodily Pain Scale. Chronic pain was defined as moderate to severe pain severity at the current and at least one prior wave; 17% had chronic pain (n=80). At the third wave, 481 participants (mean age=67.57) underwent neuromelanin-sensitive MRI scans from which we calculated an LC contrast-to-noise ratio (LCCNR) - an index of LC integrity. We examined associations between chronic pain and LCCNR (in the rostral LC and caudal regions) with generalized estimating equations after adjusting for age, race, education, depressive symptoms, medical comorbidities, and opioid medication use. Individuals with chronic pain had .35 standard deviation lower rostral LCCNR (95% CI: -.62 to -.05) compared to those without chronic pain. No differences in the caudal LCCNR were detected. Chronic pain was associated with decreased rostral LC integrity in older adults. Differences in the rostral LC, rather than caudal LC, suggest the association between lower LC integrity and chronic pain may be related to pain processing in cortical regions where rostral LC projections typically connect.