Independent and Additive Associations of Frailty and Chronic Kidney Disease with Healthcare Utilization in Community-Dwelling Older Adults: Evidence from ELSI-Brazil

Frailty is common among older adults with chronic kidney disease (CKD) and may influence healthcare utilization beyond disease burden. Evidence from community-dwelling populations in middle-income settings is limited. This study examined frailty and CKD’s independent associations with healthcare utilization among community-dwelling adults aged ≥ 50 in Brazil. Data were drawn from the second wave (2019–2021) of the Brazilian Longitudinal Study of Aging (ELSI-Brazil), a nationally representative population-based cohort. CKD was ascertained through self-reported physician diagnosis. Frailty was operationalized using a deficit accumulation Frailty Index, categorized as non-frail (FI < 0.11), pre-frail (0.11–0.20), and frail (≥ 0.21) using established thresholds. The primary outcome (hospital-based care) was defined as any hospitalization regardless of duration. Secondary outcomes included specialist visits and specialist or higher-level care. Survey-weighted logistic regression was used, adjusting for CKD, hypertension, diabetes mellitus, stroke, chronic obstructive pulmonary disease, age group, sex, and health insurance type. Robustness was assessed across sequential model specifications. The analytic sample comprised 9,432 individuals, representing a weighted population of approximately 53.8 million community-dwelling adults. Of these, 2.7% reported a CKD diagnosis. Frailty burden was substantially higher in the CKD group, with 72.1% classified as frail versus 47.5% of those without CKD. In the primary adjusted model, the frail category was associated with higher odds of hospital-based care (OR 2.01; 95% CI 1.12–3.60), whereas pre-frailty showed no significant association (OR 0.89; 95% CI 0.52–1.53). CKD was independently associated with hospital-based care (OR 2.60; 95% CI 1.56–4.35). The frailty association was consistent across all sensitivity model specifications and was concentrated at the frail threshold rather than distributed across a continuous gradient. Private health insurance was strongly associated with specialist visits (OR 3.99; 95% CI 3.08–5.17) but not with hospitalization, indicating differential access by service level. In this nationally representative sample of Brazilian older adults, frailty and CKD were independently associated with hospital-based care, with effects persisting after adjustments. The risk concentration at the frail threshold suggests that frailty assessment may identify high-risk subgroups not captured by disease-based criteria. These findings support integrating frailty screening into population-level monitoring for older adults, particularly in middle-income health systems facing aging populations and limited resources.