Nearly half of patients with chronic pain report problems in multiple body sites. They suffer from the so-called multisite chronic pain syndrome (MCP). In a recent study published in the Proceedings of the National Academy of Sciences (PNAS) in the U.S., using patients from the UK Biobank, it was shown that individuals with MCP have a significantly increased risk of dementia and decreased hippocampal volume (the hippocampus is the part of our brain in the temporal lobe that is particularly important for explicit learning and memory) compared to pain-free controls and patients with chronic pain in only one body site. This corresponds to premature aging by about 8 years.
Wenhui Zhao and colleagues first examined dementia risk in over 350,000 patients with varying numbers of coexisting pain locations. They then analyzed in more detail the risk of excessive deterioration of cognition and brain structure in 19,000 individuals. After adjusting the data for potential confounders (including different education levels, weight, smoking status, alcohol consumption, psychological distress, cancer, diabetes, or history of vascular and cardiac problems), a significant difference was found between individuals with MCP and the control groups. Thus, patients with multiple sites of pain had a higher risk of dementia, faster onset of cognitive impairment, and greater atrophy of the hippocampus as a function of the number of pain sites.
Chronic pain is complained of by about one-third of the world's population, especially at older ages. The current work shows that pain syndromes not only cause physical and psychological suffering, but can also have significant effects on our higher mental functions (memory and learning, as well as attention and concentration). Although numerous possible biological mechanisms are discussed how cognitive impairment and pain are related (e.g., due to inflammation or genetic risk factors), the exact neural mechanisms and thus causal therapeutic approaches are unfortunately still unknown.
Reference:
Zhao W, Zhao L, Chang X, Lu X, Tu Y (2023) Elevated dementia risk, cognitive decline, and hippocampal atrophy in multisite chronic pain. Proceedings of the National Academy of Sciences 120:e2215192120.
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