Chronic Pain Conditions in the Context of Aging
Chronic pain conditions are poorly understood, often incorrectly diagnosed or dismissed by medical practitioners, and, generally, have only poor and unreliable options for treatment. Given that aging degrades the function of all bodily systems, it is no surprise to find a significant incidence of chronic pain in older adults. It is an open question as to the degree to which similar mechanisms are at play to those causing chronic pain in younger adults, and whether useful information can be obtained by comparing the biochemistry of similar conditions in old and young individuals. Unfortunately there remains a lack of understanding as to what is actually going on under the hood in these diverse conditions, leading to a great deal of suffering in a large patient population.
Chronic pain is one of the most common, costly, and potentially debilitating health issues facing older adults, with attributable costs exceeding $600 billion annually. The prevalence of pain in humans increases with advancing age. Yet, the contributions of sex differences, age-related chronic inflammation, and changes in neuroplasticity to the overall experience of pain are less clear, given that opposing processes in aging interact.
This review article examines and summarizes pre-clinical research and clinical data on chronic pain among older adults to identify knowledge gaps and provide the base for future research and clinical practice. We provide evidence to suggest that neurodegenerative conditions engender a loss of neural plasticity involved in pain response, whereas low-grade inflammation in aging increases central nervous system sensitization but decreases peripheral nervous system sensitivity. Insights from preclinical studies are needed to answer mechanistic questions. However, the selection of appropriate aging models presents a challenge that has resulted in conflicting data regarding pain processing and behavioral outcomes that is difficult to translate to humans.