Operationalization of Intrinsic Capacity in Older People and Its Association With Subsequent Disability, Hospital Admission and Mortality: Results From The English Longitudinal Study of Ageing

Abstract

Background Intrinsic capacity (IC) is a new concept in the healthy ageing field and has many operationalised definitions. In this study, we operationalised IC using item response theory in the English Longitudinal Study of Ageing (ELSA) and tested the predictive value of the scale using subsequent functional ability, mortality, and hospital admission. Methods IC was measured at baseline (2004, Wave 2) using 14 dichotomous indicators: word recall, orientation in time, balance, chair rises, walking speed, upper mobility, lower mobility, eyesight, hearing, grip strength, BMI, waist circumference, depressive symptoms, life satisfaction. A two-parameter item response theory model was used to generate a scale of IC at baseline. Logistic regression was used for the prediction of subsequent difficulties, measured by difficulties with ≥1 activities of daily living (ADLs) and ≥1 instrumental activities of daily living (IADLs) at 4 and 8 years after baseline. Competing risk and cox regressions were employed to test prediction of hospital admission and mortality, respectively, over a 14-year follow-up. Results Intrinsic capacity scores were generated for 4,545 individuals aged on average 70.8 years (SD 7.93). Better baseline IC scores were associated with reduced risk of subsequent difficulties with ADLs and IADLs, hospital admission (SHR=0.99, 95%CI 0.98-0.99) and mortality (HR=0.98, 95%CI 0.98–0.99), when adjusted for sociodemographic and health-related covariates. Conclusions These results suggest the utility of this IC score as a measure of risk for future adverse outcomes in older people, potentially above that indicated by other sociodemographic and health-related factors.

Factors associated with the intrinsic capacity in older adults: A scoping review

“…Additionally, three studies (Campbell et al., 2022; Muneera et al., 2022; Yu et al., 2022b) with 30,713 participants found a significant association between occupation status and IC. And these studies discovered that older adults not in employment were more inclined to suffer IC decline.…”

“…19 of the 29 studies looked at the effect of age on the IC of older adults, involving 95,732 participants. Eighteen studies (Beard et al., 2019; Beard et al., 2022; Campbell et al., 2022; Jia et al., 2023; Leung et al., 2022; Lin et al., 2022; Lu et al., 2021; Ma et al., 2021a; Muneera et al., 2022; Prince et al., 2021; Tang et al., 2023; Wu et al., 2022; Yu et al., 2021; Yu et al., 2022a; Yu et al., 2022b; Yu et al., 2022c; Yu et al., 2023; Zhao et al., 2021) discovered a significant association between age and IC of older adults, indicating that the younger old adults were likely to have a better IC. And only one study (Ma et al., 2021c) showed no differences between age and IC of older adults.…”

“…Sixteen studies with 89,332 participants investigated the relationship between sex and IC of older adults. Thirteen studies (Beard et al., 2019; Beard et al., 2022; Campbell et al., 2022; Lin et al., 2022; Lu et al., 2021; Muneera et al., 2022; Prince et al., 2021; Tang et al., 2023; Yu et al., 2021; Yu et al., 2022b; Yu et al., 2023; Yu, Leung, et al., 2022; Zhao et al., 2021) found a significant association between sex and IC of older adults, with older females being more likely to have poorer IC. However, the other three studies (Jia et al., 2023; Wu et al., 2022; Yu et al., 2022a) did not observe such findings.…”

“…Ten studies explored an association between marital status and IC among 50,777 participants. Eight studies (Campbell et al., 2022; Lin et al., 2022; Ma et al., 2021a; Muneera et al., 2022; Yu et al., 2022a; Yu et al., 2022b; Yu et al., 2023; Zhao et al., 2021) revealed that older adults with spouses were more likely to have a better IC. However, the other two studies (Jia et al., 2023; Lu et al., 2021) failed to identify the association between marital status and IC of older adults.…”

“…In general, an individual's IC peaks in early adulthood and then gradually decreases as they get older (Beard et al., 2016). IC has been shown to be predictors for adverse health outcomes in older adults, including disability, frailty, hospitalisation, and mortality (Campbell et al., 2022; Tay et al., 2022; Yu et al., 2022a). Maintaining and improving IC can thus help prevent functional impairments and facilitate healthy aging.…”