From age to frailty: redefining chronic pain characterization

Chronic pain in older adults is highly prevalent, multifactorial, and often associated with greater intensity, multisite involvement, and functional impairment. Despite its burden, it remains frequently underdiagnosed and undertreated. Chronological age alone does not adequately capture biological vulnerability or interindividual variability in pain expression. To examine the associations of frailty, an indirect marker of biological age, and chronological age with chronic pain characteristics. We conducted a cross-sectional study including 455 adults (≥18 years) recruited from primary care. Thirty-three pain characteristics were assessed through structured interviews. Frailty was quantified using a 31-item Frailty Index based on the deficit accumulation model. Associations of frailty, chronological age, and sex with each pain variable were analyzed using multivariable linear and logistic regression models. Most pain characteristics were more consistently associated with frailty than with chronological age, although effect sizes were modest (sr2 typically 1–5%). Frailty correlated with greater pain intensity (sr 0.23, r2 5.3%), higher frequency (sr 0.10, r2 1.1%), and continuous or mixed-type pain (OR 0.97, 95% CI 0.95–0.99). In contrast, chronological age primarily predicted temporal aspects, including pain duration, diagnostic delay, and time to first analgesic prescription. Age and frailty showed opposite directions of association for certain domains, such as accompanying symptoms and daily pain duration. Frailty provides complementary information to chronological age in characterizing chronic pain. Integrating frailty assessment into routine pain evaluation may enable more individualized management, enhance pain control, and reduce age-related disparities in clinical care. Frailty, as a proxy for biological age, showed more consistent associations than chronological age with several chronic pain characteristics, including intensity, mixed-type pain, continuous course, and accompanying symptoms. Integrating frailty assessment into pain evaluation offers a biologically grounded and individualized framework, particularly relevant for aging populations.