Persistent pain is associated with accelerated memory decline and development of dementia in the elderly.
According to researchers, elderly patients who reported having persistent pain experienced an accelerated decline in functional independence. After 10 years, the additional amount of memory decline expected in participants with persistent pain shows they would be significantly less likely to manage medications and finances independently compared with controls.
“Based on these results, there is a small but statistically significant rate of accelerated cognitive decline and dementia in persistent pain sufferers,” said Elizabeth L. Whitlock, MD, MSc, a postdoctoral anesthesiologist at the University of California, San Francisco (UCSF) School of Medicine. “Care providers should be aware of this association, which may help identify patients at higher risk for current and incident cognitive impairment.”
As Dr. Whitlock reported, chronic pain is prevalent among the elderly and has been associated with decrements in cognitive function in cross-sectional studies, particularly in attentional and memory domains. It is unclear, however, whether these findings represent accelerated cognitive decline.
“These outcomes could be due to lower cognitive baseline, a faster rate of cognitive decline or potentially some combination of the two,” Dr. Whitlock explained. “ We set out to explore which of these cognitive trajectories would be most consistent with the known finding that chronic pain is associated with cognitive deficits.”
Faster Rate of Mental Decline
Using data from the Health and Retirement Study (HRS), a population-based longitudinal study of elders sponsored by the National Institute on Aging, Dr. Whitlock and her colleagues from the UCSF Division of Geriatrics modeled the association between persistent pain at cohort inception and measures of memory and dementia probability over the following 12 years. Participants who were at least 62 years of age in 2000 and answered pain and cognition questions by self-report in both 1998 and 2000 were included in the study. Those who reported their pain as either moderate or severe in both 1998 and 2000 were considered to have persistent pain.
Investigators then estimated composite memory score and dementia probabilities by combining HRS cognitive test results and/or proxy ratings of participants’ cognition, which were tracked until the 2012 interview or patient dropout. A linear mixed-effects model with random slope and intercept for each participant adjusted for various economic, demographic and health factors. Finally, to quantify the possible effect of persistent pain on functional independence, the researchers combined their primary results with information on the association between memory and dependence in ability to manage medications and finances.
As Dr. Whitlock reported at the International Anesthesia Research Society 2017 annual meeting (abstract 1596), of the 10,065 participants in the final cohort, 10.9% met the definition for persistent pain. The persistent pain group reported pain at 69% of subsequent interviews, suggesting this approximates a chronic pain phenotype, Dr. Whitlock said. Moreover, after covariate adjustment, persistent pain was associated with 9.2% (95% CI, 2.8%-15.0%) more rapid memory decline compared with controls.
“It’s difficult to understand what a memory score really means in real life, so we extended these results to implications of chronic pain on memory score after 10 years of pain,” Dr. Whitlock explained. “After 10 years, a participant is 12% less likely to be able to manage their own finances independently and 16% less likely to be able to manage their own medications independently, so there are potentially real functional consequences to this finding.”
Dr. Whitlock and her colleagues also observed an accelerated probability of developing dementia in the persistent pain group. Adjusted dementia probability increased 7.7% faster (95% CI, 0.5%-14.2%) for those with persistent pain compared with controls, she reported.
Barriers to Analysis
Dr. Whitlock acknowledged that these findings could be an artifact of residual confounding, a common limitation to all secondary data studies. However, Dr. Whitlock suggested that persistent pain could be used as a marker to identify populations at risk for increased cognitive problems later in life. The cohort with persistent pain also had increased functional limitations, higher rates of depressive symptoms and poorer health at baseline, revealing that persistent pain could be used to identify a population with particularly high care needs.
There are other potential explanations—none of which are mutually exclusive—for this finding. “It’s believed that chronic pain competes for attentional resources in terms of memory encoding, so persistent pain could have a direct effect on cognition. “Also, this association may be mediated by another factor,” she said. “For example, opioid consumption, which was not available in our data set, may influence cognition.”
Moderator of the session, Beverley Orser, MD, PhD, FRCPC, professor of physiology and anesthesia at the University of Toronto, inquired about the study’s possible clinical implications.
“Even if residual confounding played a role, at the very least, elders who are reporting chronic pain are at increased risk for cognitive decline,” Dr. Whitlock said. “That means that providers should probably be instituting plans to identify a durable power of attorney, to assist with medication management and to provide other means of cognitive support for these patients who are at increased risk.”