Although chronic pain is a recognized risk factor for cognitive decline and dementia, often mediated by depression, it remains unclear whether depression plays a differential mediating role across chronic pain duration in the pathway to dementia.

We conducted a cross-sectional analysis of data from 1096 adults aged ≥45 years, obtained from the Inpatient Comprehensive Assessment Database (2020−2023) of the Department of Geriatrics at The First Affiliated Hospital of Chongqing Medical University. Chronic pain was defined as self-reported pain persisting for over three months. Based on chronic pain duration, participants were categorized as: chronic pain-free, 3–24 months, or > 24 months. Dementia was diagnosed using education-stratified cutoff scores on the Mini-Mental State Examination (MMSE), and depression was assessed with the Patient Health Questionnaire-9 (PHQ-9). Data were analyzed using chi-square tests, binary logistic regression, and mediation analysis (PROCESS macro).

After adjusting for potential confounders, multivariable logistic regression models revealed that the prevalence of dementia was significantly higher in individuals with chronic pain than in those without. Furthermore, a longer pain duration (>24 months) was associated with a significantly increased risk of dementia compared to a shorter duration (3–24 months) (OR = 2.60, p < 0.05; OR = 1.78, p < 0.05). Mediation analysis indicated that depression fully mediated the association in the chronic pain (3–24 months) group, but only partially in the >24 months group.

Chronic pain duration is significantly associated with dementia, with depression playing a differential mediating role across chronic pain durations.