Validating intrinsic capacity to measure healthy aging in an upper middle-income country: Findings from the ELSI-Brazil

Abstract

Background: While efforts have been made to validate intrinsic capacity (IC) as a multidimensional indicator of healthy aging in high-income countries, we still need evidence from lower-income countries. We examined associations of IC with wide ranges of activities of daily living in a nationally representative sample of Brazilians aged≥50 years.

Methods: This cross-sectional analysis included 7175 participants from the Brazilian Longitudinal Study of Aging. IC domains (cognitive, psychological, sensory, locomotor, and vitality) were determined using self-reported and physical performance measures. IC was operationalized through factorial analysis. We investigated associations of IC and its domains with functional ability in basic, instrumental, and advanced activities of daily living (ADL, IADL, and AADL) using logistic regressions adjusted for sociodemographic, clinical, and modifiable risk factors.

Findings: The IC bi-factorial model revealed satisfactory goodness-of-fit. Preserved ability in ADL and IADL, respectively, ranged from 69% and 29% to 89% and 74% across IC quartiles. In adjusted analyses, every standard deviation increment in IC composite score was associated with almost twice the odds of preserved ADL (OR=1·72; 95%CI=1·54-1·93), preserved IADL (OR=1·95; 95%CI=1·77-2·16), and high performance in AADL (OR=1·79; 95%CI=1·59-2·00). Similar results were reported using the IC domains as predictors. Although age, race/ethnicity, and education did not modify associations of IC with functional ability, we found sex differences with stronger relationships of IC with preserved ADL or IADL in females.

Interpretation: Our results support IC validity and reliability to measure healthy aging in diverse socioeconomic and cultural settings. Incorporating IC in routine practices can promote holistic and person-centered care approaches in aging societies.

Funding: The Brazilian Ministry of Health and Ministry of Science, Technology, Innovation, and Communication.

Keywords: AADL, Advanced Activities of Daily Living; ADL, Activities of Daily Living; Activities of daily living; CES-D, Center for Epidemiologic Studies Depression Scale; Developing countries; ELSI-Brazil, The Brazilian Longitudinal Study of Aging; Functional status; Gender diversity; Geriatric assessment; Healthy aging; IADL, Instrumental Activities of Daily Living; IC, Intrinsic Capacity; Intrinsic capacity; LMICs, Low- and Middle-income Countries.

Figure 1

Bi-factor confirmatory factor analysis model of intrinsic capacity.

Figure 2

Interaction of sex and intrinsic capacity on preserved functional ability in routine activities among people aged 50 years and older (n = 7,175). (A) Activities of daily living (ADL); (B) Instrumental activities of daily living (IADL). Preserved ADL (i.e., bathing, dressing, toileting, transferring, continence, and eating) and preserved IADL (i.e., handling finances, taking medications, using transportation, doing laundry, housekeeping, preparing food, shopping, and using the telephone) were defined for those doing the activities without difficulty or need for help from another person. P for interaction between intrinsic capacity and sex for preserved ability in ADL = 0·04. P for interaction between intrinsic capacity and sex for preserved ability in IADL = 0·001.

Figure 3

Prevalence of ability to perform ADL and IADL with or without functional impairment according to quartiles of intrinsic capacity stratified by sex. (A) Female participants, n = 3,979; (B) Male participants, n = 3,196. Comparisons investigating differences among the quartiles of intrinsic capacity showed a p-value <0·001 for female and male participants.