Association of chronic pain and analgesic use with the risks of Parkinson's and Alzheimer's disease.

Chronic pain and analgesic use are linked to increased Parkinson's disease (PD) and dementia risk, but the effects of each individually and when both are present remain unclear. This study examined whether chronic pain and analgesic use, separately and together, are associated with the incident risk of these conditions. A total of 355,709 participants (mean age 56.51, 48.4% male) free of parkinsonism and dementia at baseline were included. Chronic musculoskeletal pain lasting ≥ 3 months and regular use of analgesics, including paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), opioids, and antidepressants, were recorded. Incidence of PD, Alzheimer's disease (AD), all-cause parkinsonism, and all-cause dementia was recorded. Cox regression assessed associations with covariate adjustments. During a 13-year follow-up, 2035 individuals developed PD, 2052 developed AD, 2281 developed all-cause parkinsonism, and 4778 developed all-cause dementia. Compared to participants without chronic pain and analgesic use, those with chronic pain, those using analgesics, and those with both had higher risks of developing PD and AD. In the fully adjusted model, chronic pain showed hazard ratios (HRs) ranging from 1.16 to 1.22 for PD and 1.18 to 1.24 for AD. Among analgesics, only antidepressants increased PD risk (HR 1.77, 95% CI 1.37-2.29), while HRs for AD ranged from 1.22 to 1.57. Those with chronic pain who regularly used analgesics had a higher risk, with HRs ranging from 1.23 to 1.98 for PD and 1.44 to 2.19 for AD. Similar patterns emerged for all-cause parkinsonism and all-cause dementia. Chronic pain and analgesic use are associated with developing parkinsonism and dementia, with an additive effect in individuals with chronic pain who regularly use analgesics.