The mediating role of activities of daily living in the association between intrinsic capacity and health-related quality of life: evidence from the WHO ICOPE pilot in China

Abstract

Background

Intrinsic capacity (IC) is a core concept of the World Health Organization’s (WHO) Integrated Care for Older People (ICOPE), representing the composite of an individual’s physical and mental reserves. While deficits in IC are associated with reduced health-related quality of life (HRQoL), the functional mechanisms underlying this relationship, particularly the role of functional independence as measured by activities of daily living (ADL) remains underexplored. We investigated whether ADL performance mediates the association between IC and HRQoL among Chinese older adults.

Methods

In this cross-sectional analysis, 468 community-dwelling and institutionalized adults aged 60 years and older were recruited from the WHO ICOPE pilot in Lianyungang, China. Cumulative IC impairment was evaluated across five domains (cognition, locomotion, nutrition, sensory function, and psychology) using the ICOPE screening tool. ADL dependence was quantified by the Modified Barthel Index, and HRQoL was measured using the EQ-5D-3 L instrument. Multivariable logistic regression was employed to estimate the association between IC and HRQoL, adjusting for sociodemographic and clinical covariates. A nonparametric bootstrap mediation analysis (5000 resamples) quantified the indirect effect of IC on HRQoL via ADL.

Results

After adjusting for covariates, each one-point increase in Cumulative IC Impairment Score was associated with 46% higher odds of impaired HRQoL (adjusted OR = 1.46; 95% CI: 1.26–1.69; p < 0.001). ADL dependence mediated approximately 34.1% of this association (indirect effect = 0.028; 95% CI: 0.006–0.050; p = 0.013). Subgroup analyses revealed that the IC-HRQoL association was significantly stronger among urban residents compared to suburban residents (interaction p = 0.004) and among community-dwelling older adults compared to nursing home residents (interaction p = 0.043).

Conclusions

Intrinsic capacity impairment is associated with compromised HRQoL both directly and indirectly by exacerbating functional dependence. Preserving functional independence serves as a key pathway connecting intrinsic capacity to well-being. These findings highlight the imperative for integrated interventions that simultaneously bolster intrinsic capacity and support daily functional ability, tailored to diverse living environments to promote healthy aging.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40520-026-03347-x.

Introduction

Population aging is accelerating worldwide, driven by declining fertility and increased longevity, placing a growing strain on health and social systems [1]. In response, the World Health Organization (WHO) has redefined healthy aging as “the process of developing and maintaining functional ability that enables well-being in older age” [2]. Within this framework, quality of life (QoL), an individual’s subjective appraisal of their life circumstances, has become a pivotal outcome measure [3]. However, QoL is inherently multidimensional, encompassing physical health, symptom burden, and psychosocial adaptation, which complicates comparison across studies [4]. To enhance specificity, researchers have adopted the construct of health-related quality of life (HRQoL), which focuses explicitly on health status, disease impact, and treatment outcomes [5]. Given older adults’ heightened susceptibility to functional decline and multimorbidity, HRQoL has emerged as a central endpoint in geriatric research, driving a shift from single-disease management toward comprehensive interventions that support independence and social engagement [6].

Concurrently, the WHO has emphasized the importance of intrinsic capacity (IC) [7], defined as the composite of an individual’s physical and mental reserves [8]. IC is a multidimensional construct encompassing cognition, psychological well-being, vitality, sensory functions, and locomotion [7]. Unlike traditional approaches that prioritize disease counts or established functional deficits, IC offers a proactive metric for health trajectories, facilitating the early detection of decline and the prediction of adverse outcomes [8]. Empirical evidence indicates that higher IC promotes healthy aging, whereas declines in IC predict disability, frailty progression, and increased mortality risk [9–11]. Although several studies have demonstrated an association between preserved IC and better HRQoL, the underlying mechanisms linking these two constructs have yet to be fully elucidated. Understanding these pathways is critical for designing interventions that effectively preserve functional ability and enhance quality of life in older populations.

According to the WHO’s International Classification of Functioning, Disability and Health (ICF) framework, functional performance arises from dynamic interactions between intrinsic capacity and environmental factors [12]. A plausible mechanism linking IC to HRQoL is functional independence, often operationalized via performance in activities of daily living (ADL). Declines in specific IC, such as mobility or cognition, can directly undermine ADL performance, which in turn diminishes HRQoL [13]. Basic self-care tasks (e.g., bathing, dressing, eating) are foundational to autonomy and well-being; consequently, limitations in ADLs and instrumental activities of daily living (IADLs) strongly correlate with poorer HRQoL [14]. While theoretical models posit that IC influences HRQoL through functional pathways, empirical verification of this mediation remains limited. Prior research has primarily examined direct IC-HRQoL associations [10, 15] or focused on the relationship between IC and frailty [16], leaving a critical gap concerning the mediating role of ADL performance.

To address this gap, we analyzed data from the WHO Integrated Care for Older People (ICOPE) pilot in Lianyungang City, Eastern China, a region characterized by integrated community and institutional eldercare. We aimed to evaluate a mediation model (IC → ADL → HRQoL) in 468 adults aged 60 years and older. Grounded in the ICF and ICOPE frameworks, we quantified the total effect of IC on HRQoL and the proportion mediated by ADL dependence. Specifically, considering the scoring metrics where higher scores indicate greater deficit, we hypothesized that: (1) Cumulative IC impairment is positively associated with Impaired HRQoL; (2) Cumulative IC impairment is positively associated with ADL dependence; (3) ADL dependence is positively associated with Impaired HRQoL; and (4) ADL dependence mediates the relationship between IC impairment and HRQoL impairment.

Materials and methods

Data source and study design

This cross-sectional analysis utilized data from the WHO ICOPE pilot program conducted in Lianyungang City, China, from April to July 2024. Participants were recruited via convenience sampling from community health centers and nursing homes. The inclusion criteria were: (1) age 60 years or older; (2) clear consciousness with the ability to cooperate and complete all assessment items; and (3) provision of voluntary written informed consent. The exclusion criteria were: (1) presence of severe mental disorders or critical illnesses; and (2) individuals with missing data for key variables. Of the 509 older adults initially screened, 468 met the eligibility criteria and were included in the final analysis (Fig. 1).

Fig. 1.

Flow chart of the study population

Measures

Data collection was performed by trained personnel using structured questionnaires and validated assessment tools. Rigorous quality control procedures, including dual data entry and consistency checks, were implemented to ensure accuracy.

Intrinsic capacity (IC) assessment

IC was evaluated using the WHO ICOPE framework [2], encompassing five domains assessed via six functional measures: cognition, locomotion, nutrition, sensory function (vision and hearing), and psychology [17]. Following WHO recommendations, we employed a stepwise assessment approach using standardized scales [18]. To align with the objective of measuring deficits, we calculated a Cumulative IC Impairment Score ranging from 0 to 8, where higher scores indicate greater impairment.

The scoring algorithms for the specific domains were defined as follows. Cognition was evaluated using the Mini-Mental State Examination (MMSE), a widely used and validated screening tool [19]. Scores were adjusted for education level, with normal performance coded as 0 and impairment coded as 1. Locomotion was assessed using the Short Physical Performance Battery (SPPB). A score of 9–12 indicates normal mobility (coded as 0), while a score of 0–8 indicated impairment (coded as 1) [20]. Nutrition was measured using the Mini Nutritional Assessment-Short Form (MNA-SF). Scores ≥ 11 were classified as normal (coded as 0), and scores ≤ 10 indicated malnutrition or risk (coded as 1) [21]. Vision, hearing, and psychology were assessed based on clinical expert consensus items. Vision was assessed via three items: (1) difficulty reading, walking, or watching TV; (2) feeling obstructed or having blind spots when looking at objects; and (3) seeing objects as distorted or warped. Based on the count of affirmative responses (“yes”), vision was classified as “good” (total count ≤ 1, coded as 0), “poor” (count = 2, coded as 1), or “very poor” (count = 3, coded as 2). Hearing was assessed via three items: (1) others complaining about TV/radio volume; (2) frequently needing repetition; and (3) difficulty hearing on the phone. Similarly, hearing was classified as “good” (total count ≤ 1, coded as 0), “poor” (count = 2, coded as 1), or “very poor” (count = 3, coded as 2). Psychology was assessed using a two-item screening tool regarding feelings of depression, hopelessness, or loss of interest. Answering “yes” to at least one question indicated the presence of depressive symptoms (coded as 1); while absence was coded as 0.

The Cumulative IC Impairment Score was calculated by summing the scores of these six functions. The total score ranged from 0 to 8, with higher scores indicating a greater accumulation of deficits. For analytical purposes, participants were categorized into three groups: Low Impairment (score < 2), Moderate Impairment (score 2–3), and High Impairment (score ≥ 4).

Health-related quality of life (HRQoL) assessment

HRQoL was measured using the EQ-5D-3 L instrument developed by the EuroQol Group [22]. This scale assesses five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. It has demonstrated good reliability and validity across various populations [23, 24]. Given the previous literature, statistical balance, and clinical experience, we dichotomized the outcome variable [25]. Participants with a score of 0 (indicating no problems in any dimension) were classified as the “Full Health” group (coded as 0), while those reporting problems in at least one dimension (score 1–3) were classified as the “Impaired HRQoL” group (coded as 1). Thus, the outcome variable reflects the presence of any HRQoL deficit [26].

Activities of daily living (ADL) assessment

Functional independence was evaluated using the Modified Barthel Index (MBI) [27]. To align with the impairment-focused framework of the mediation model, raw MBI scores (0-100) were reclassified into an ordinal ADL Dependence Score ranging from 0 to 4: 0 = No disability (MBI 100); 1 = Mild dependence (MBI 91–99); 2 = Moderate dependence (MBI 61–90); 3 = Severe dependence (MBI 21–60); 4 = Complete dependence (MBI ≤ 20). Higher scores on this scale indicate greater functional limitation.

Covariates

We adjusted for sociodemographic factors (age, sex, marital status, education, residential area), nursing home residency, caregiver availability. Multimorbidity was assessed using a composite index derived from the Charlson Comorbidity Index [28] and the Cumulative Illness Rating Scale for Geriatrics (CIRS-G) [29].

Statistical analysis

All analyses were performed using the statistical software packages R (http://www.r-project.org, The R Foundation) and Free Statistics software versions . First, baseline characteristics were compared across IC categories using Chi-square tests, and the linearity of the IC-HRQoL relationship was verified using restricted cubic spline analysis. Second, the association between Cumulative IC Impairment and Impaired HRQoL was estimated using multivariable logistic regression. We calculated odds ratios (ORs) with 95% confidence intervals (CIs). Model fit was evaluated using the Hosmer-Lemeshow test and Nagelkerke R², while multicollinearity was checked using variance inflation factors (VIF). Sensitivity analyses (Tobit and ordinal regression) were conducted to validate the robustness of the dichotomized HRQoL outcome. Finally, mediation analysis was conducted to quantify the role of ADL dependence. We employed a nonparametric bootstrap approach (5000 resamples) to estimate the total effect, average direct effect (ADE), and average causal mediation effect (ACME). Interaction terms were included to assess effect modification by residential setting and care status. Statistical significance was set at p < 0.05 (two-sided).

Results

Baseline characteristics

The study sample comprised 468 older adults, including 261 women (55.8%) and 207 men (44.2%). Based on the Cumulative IC Impairment Score, 196 participants (41.9%) were classified as having Low Impairment (score < 2), 138 (29.5%) as Moderate Impairment (score 2–3), and 134 (28.6%) as High Impairment (score ≥ 4).

Univariate analyses revealed significant differences across IC categories (Table 1). Compared to the Low Impairment group, participants in the High Impairment group were significantly older (59.6% aged ≥ 80 years), had lower educational attainment, and were more likely to reside in nursing homes. Notably, the prevalence of ADL dependence and Impaired HRQoL increased progressively with the severity of IC impairment (p < 0.001), confirming a gradient of functional decline.

Table 1.

Baseline characteristics of participants stratified by intrinsic capacity (IC) Impairment (N = 468)

Variables	Total(N = 468)	Low Impairment (< 2) (n = 196)	Moderate Impairment (2–3) (n = 138)	High Impairment (≥ 4) (n = 134)	P value
Sex, n (%)					0.027
Female	261 (55.77)	123 (62.76)	67 (48.55)	71 (52.99)
Male	207 (44.23)	73 (37.24)	71 (51.45)	63 (47.01)
Age, n (%)					< 0.001
< 80 years	189 (40.38)	86 (43.88)	37 (26.81)	66 (49.25)
≥ 80 years	279 (59.62)	110 (56.12)	101 (73.19)	68 (50.75)
Education, n (%)					0.128
Illiterate	157 (33.55)	74 (37.76)	48 (34.78)	35 (26.12)
Primary school	142 (30.34)	52 (26.53)	47 (34.06)	43 (32.09)
Junior high school and above	169 (36.11)	70 (35.71)	43 (31.16)	56 (41.79)
Marital Status, n (%)					< 0.001
Married	221 (47.22)	88 (44.90)	49 (35.51)	84 (62.69)
Unmarried	247 (52.78)	108 (55.10)	89 (64.49)	50 (37.31)
Residential Area, n (%)					0.022
Urban	303 (64.74)	116 (59.18)	88 (63.77)	99 (73.88)
Suburban	165 (35.26)	80 (40.82)	50 (36.23)	35 (26.12)
Multimorbidity, n (%)					< 0.001
No	171 (36.54)	60 (30.61)	40 (28.99)	71 (52.99)
Yes	297 (63.46)	136 (69.39)	98 (71.01)	63 (47.01)
Nursing Home Residency, n (%)					< 0.001
No	253 (54.06)	105 (53.57)	49 (35.51)	99 (73.88)
Yes	215 (45.94)	91 (46.43)	89 (64.49)	35 (26.12)
Caregiver Availability, n (%)					0.102
No	346 (73.93)	136 (69.39)	103 (74.64)	107 (79.85)
Yes	122 (26.07)	60 (30.61)	35 (25.36)	27 (20.15)
ADL Dependence, n (%)					< 0.001
Independent (Score 0)	335(71.58)	120(89.55)	82(59.42)	133(32.14)
Dependent (Score 1–4)	133(28.42)	14(10.45)	56(40.58)	63(67.86)
HRQoL Impairment, n (%)					< 0.001
Full Health (Score 0)	322 (68.80)	115 (85.82)	77 (55.80)	130 (66.33)
Impaired (Score 1–3)	146 (31.20)	19 (14.18)	61 (44.20)	66 (33.67)
ADL Dependence Score, (IQR)	0 (0, 1)	0 (0, 0)	0 (0, 1)	0 (0, 1)	< 0.001
HRQoL Impairment Score, (IQR)	0 (0, 1)	0 (0, 0)	0 (0, 1)	0 (0, 2)	< 0.001

Unmarried includes never married, widowed, divorced, or separated. P values derived from Chi-square tests for categorical variables and Kruskal-Wallis tests for continuous scores (Median [Q1, Q3]).

Association between intrinsic capacity and HRQoL

Multivariable logistic regression confirmed a robust association between IC impairment and HRQoL (Table 2). In the fully adjusted model (Model 3), each one-point increase in the Cumulative IC Impairment Score was associated with 46% higher odds of reporting impaired HRQoL (Adjusted OR = 1.46; 95% CI: 1.26–1.69; p < 0.001). When analyzed categorically, a dose-response relationship was evident. Compared to the Low Impairment group, participants with Moderate Impairment had 2.40 times the odds of impaired HRQoL (95% CI: 1.32–4.38), while those with High Impairment faced a 4.36-fold increase in odds (95% CI: 2.29–8.32). Restricted cubic spline analysis confirmed that this relationship was linear (p for non-linearity = 0.153; Supplementary Fig. 1).

Table 2.

Multivariable logistic regression analysis of the association between intrinsic capacity impairment and impaired HRQoL

Variables	Crude Model OR (95% CI)	Model 1 OR (95% CI)	Model 2 OR (95% CI)	Model 3 OR (95% CI)
Continuous IC Score	1.46 (1.28–1.66) ***	1.49 (1.29–1.71) ***	1.43 (1.24–1.65) ***	1.46 (1.26–1.69) ***
Cumulative IC Impairment
Low Impairment (< 2)	Ref	Ref	Ref	Ref
Moderate Impairment (2–3)	3.07 (1.74 ~ 5.43) ***	2.93 (1.64 ~ 5.23) ***	2.34 (1.29 ~ 4.26) **	2.40 (1.32 ~ 4.38) **
High Impairment (≥ 4)	4.79 (2.66 ~ 8.65) ***	5.00 (2.70 ~ 9.25) ***	4.03 (2.15 ~ 7.55) ***	4.36 (2.29 ~ 8.32) ***

Model 1 adjusted for age, sex, marital status, education, and residential area. Model 2 further adjusted for multimorbidity. Model 3 further adjusted for nursing home residency and caregiver availability.

OR: Odds Ratio; CI: Confidence Interval.

*p<0.05, **p<0.01, ***p<0.001.

Subgroup analysis

Subgroup analyses indicated that the detrimental association between IC impairment and HRQoL was consistent across most strata (Table 3). However, significant effect modification was observed by residential setting. The association was more pronounced among urban residents (OR = 1.68) compared to suburban residents (OR = 1.08; interaction p = 0.004). Similarly, the association was stronger among community-dwelling older adults (OR = 1.66) than among nursing home residents (OR = 1.30; interaction p = 0.043).

Table 3.

Subgroup analyses of the association between intrinsic capacity and HRQoL impairment

Models adjusted for age, sex, marital status, education, residential area, multimorbidity, nursing home residency, and caregiver availability (excluding the stratification variable itself).

Mediation analysis

Mediation analysis was conducted to quantify the role of functional independence. As shown in the path diagram (Fig. 2), IC impairment had a significant positive effect on ADL dependence (Path a: β = 0.120, p = 0.012), and ADL dependence strongly predicted HRQoL impairment (Path b: β = 0.644, p < 0.001). The bootstrap analysis revealed a significant indirect effect of IC on HRQoL via ADL (Effect = 0.028; 95% CI: 0.006–0.050; p = 0.013). The proportion of the total effect mediated by ADL dependence was 34.1% (95% CI: 9.3%–56.0%). Detailed decomposition of effects is provided in Supplementary Table S3.

Fig. 2.

Path diagram of the mediation model linking Intrinsic Capacity (IC) Impairment to Health-Related Quality of Life (HRQoL) Impairment via Activities of Daily Living (ADL). Note: Values on paths represent standardized coefficients (β). Path a: Association between IC Impairment and ADL Dependence. Path b: Association between ADL Dependence and HRQoL Impairment.Path c': Direct effect of IC Impairment on HRQoL Impairment. All scales are scored such that higher values indicate greater impairment/dependence.*p < 0.05, **p < 0.01, ***p < 0.001.

Discussion

Using data from the WHO ICOPE pilot in China, this study constitutes one of the first empirical efforts to quantify the mediating role of functional independence in the relationship between intrinsic capacity (IC) and health-related quality of life (HRQoL) among older adults across both community and institutional settings. We observed a robust, dose-dependent association even after adjusting for potential confounders, greater cumulative IC impairment significantly increased the odds of reporting impaired HRQoL. Mediation analysis revealed that approximately one-third (34.1%) of the total effect of IC on HRQoL is transmitted through ADL pathways. This implies that the accumulation of IC deficits diminishes quality of life not only through direct physiological burdens but also, substantially, by eroding the functional independence required for daily living.

Consistent with the WHO’s healthy aging framework, our findings confirm that intrinsic capacity is a potent determinant of well-being [10, 30, 31]. We found that compared to individuals with low IC impairment, those with moderate and high impairment faced a 2.4-fold and 4.4-fold increase in the odds of impaired HRQoL, respectively. Since IC represents the composite of physical and mental reserves, encompassing cognition, locomotion, sensory function, vitality, and psychology, deficits in these domains fundamentally restrict an individual’s ability to interact with their environment [32]. The direct effect observed in our model (accounting for about 66% of the total effect) suggests that IC decline compromises well-being through mechanisms beyond basic self-care disability, such as chronic pain, emotional distress, reduced social participation, and a diminished sense of autonomy [33, 34]. These results validate the utility of the ICOPE screening tool as a proactive metric for identifying older adults at risk of deteriorating quality of life before overt disability sets in [35].

We also observed a strong association between IC and ADL performance, in line with previous research [36–38]. Specifically, individuals with lower IC exhibited a higher prevalence of ADL dependence, whereas preserved IC corresponded to superior ADL function. Declines in mobility (e.g., muscle strength, gait) and cognition can directly compromise one’s ability to perform self-care; for instance, reduced lower-body strength hampers standing or walking, and cognitive decline impairs medication adherence and management of complex tasks. Longitudinal studies confirm that IC deterioration predicts subsequent ADL impairment [38], positioning IC decline as a key determinant of functional dependence in older adults. Independent ADL ability profoundly influences HRQoL. Basic ADLs, such as bathing, dressing, eating [39], and mobility are foundational to autonomy, self-esteem, and well-being; Limitations in these tasks increase dependency and substantially diminish HRQoL [39]. Instrumental ADLs, such as managing finances, meal preparation, transportation are equally vital for maintain independence and HRQoL among community-dwelling older adults. Prior research has demonstrated that deficits in ADL and IADL mediate the relationship between multimorbidity and HRQoL, underscoring the central role of functional independence in healthy aging [40].

A key contribution of this study is the quantification of the ADL-mediated pathway. While prior theoretical models posit that functional ability arises from the interaction of IC and the environment [12], our data provide statistical evidence that ADL dependence is a critical intermediate link. Specifically, declines in domains such as mobility (e.g., muscle weakness, gait instability) and cognition directly undermine the execution of basic self-care tasks [36], which in turn precipitates a decline in HRQoL. The loss of independence in activities such as bathing, dressing, or eating strikes at the core of human dignity and autonomy, thereby exerting a profound negative impact on perceived quality of life [39, 40]. However, it is imperative to interpret these mediation results with caution. While our statistical model supports the pathway IC → ADL → HRQoL, the cross-sectional design precludes definitive causal inference. It is theoretically plausible that reverse causation exists; for instance, existing functional disability or poor quality of life could accelerate the erosion of intrinsic capacity through physical deconditioning or depressive cycles [41]. Thus, our findings should be viewed as identifying associational pathways consistent with the WHO ICF framework, rather than confirming a strict unidirectional causal sequence.

Our subgroup analyses revealed that the association between IC and HRQoL is significantly modified by residential context, aligning with the ecological theory of aging [42, 43]. We found that the protective effect of preserved IC on HRQoL was weaker in suburban areas and nursing homes compared to urban community settings. This disparity may be interpreted through the lens of environmental deprivation and resource availability. Urban environments typically offer better access to healthcare, age-friendly infrastructure, and community resources, allowing older adults to fully leverage their intrinsic capacity to maintain a high quality of life [42, 44]. Conversely, in suburban areas, infrastructural barriers (e.g., lack of accessible transportation, limited healthcare) may impose a “ceiling effect” on QoL [45], where environmental constraints limit well-being regardless of an individual’s physical capacity [43]. Similarly, the attenuated association among nursing home residents may reflect the overriding influence of the institutional environment. In nursing homes, strict routines and differential social engagement opportunities can decouple individual capacity from subjective quality of life [46, 47]. Furthermore, the comprehensive care provided in institutions may buffer the negative impact of capacity loss on daily life, where basic needs are met by staff regardless of the residents’ ability, whereas community-dwelling adults rely more heavily on their own capacity to navigate daily challenges. These findings highlight that environmental context is not merely a backdrop but an active moderator of the capacity-wellbeing relationship [48].

These findings reinforce the imperative for the WHO ICOPE approach, which advocates for the early detection and management of IC declines [49]. Strategies must simultaneously target the restoration of IC domains (e.g., nutritional supplementation [50], cognitive training [51]) and the support of ADL function (e.g., assistive devices [52], rehabilitation [53]). Interventions must be tailored to the living environment. In community settings, particularly in resource-limited suburban areas, public health efforts should focus on age-friendly environmental modifications (e.g., safe walkways, community centers) to remove barriers that prevent older adults from utilizing their capacity [54]. In institutional settings, care models should shift from task-oriented care to person-centered care that fosters autonomy and meaningful engagement, ensuring that residents’ remaining capacities are nurtured and translated into well-being [55, 56].

Limitations

First, the cross-sectional design limits causal inference among IC, ADL, and HRQoL. Longitudinal studies are needed to track the temporal sequence of these interactions. Second, selection bias is a significant concern. Participants were recruited via convenience sampling from community health centers and nursing homes. This likely resulted in an over-representation of individuals receiving formal care and those with higher multimorbidity compared to the general older population. Consequently, the prevalence of IC impairment and ADL dependence observed here may be higher than in a random community sample. Third, the inclusion of nursing home residents introduces a potential environmental buffering effect. The availability of professional care in institutions might mitigate the negative impact of ADL deficits on HRQoL, suggesting that the strength of the mediation pathway observed in our mixed sample might differ from that in a purely community-based population lacking formal support. Finally, reliance on self-reported measures for HRQoL may introduce recall or social desirability bias.

Conclusion

This study provides empirical evidence that intrinsic capacity impairment exerts both direct and indirect deleterious effects on health-related quality of life, with approximately one-third of the total effect mediated by functional dependence. These findings corroborate the WHO ICOPE framework and highlight that the translation of capacity into well-being is significantly modulated by functional ability and environmental context. To promote healthy aging, integrated care models must go beyond disease management to proactively bolster intrinsic capacity, support functional independence, and crucially adapt environmental resources to the specific needs of older adults in diverse living settings.

Supplementary Information

Below is the link to the electronic supplementary material.

Abbreviations

ACME

Average causal mediation effect

ADE

Average direct effect

ADL

Activities of daily living

AUC

Area under the curve

BADL

Basic activities of daily living

CCI

Charlson comorbidity index

CI

Confidence interval

CIRS-G

Cumulative illness rating scale for geriatrics

HRQoL

Health-related quality of Life

IADL

Instrumental activities of daily living

IC

Intrinsic capacity

ICF

International classification of functioning, disability and health

ICOPE

Integrated care for older people

MBI

Modified barthel index

MMSE

Mini-mental state examination

MNA-SF

Mini nutritional assessment-short form

OR

Odds ratio

RCS

Restricted cubic spline

SPPB

Short physical performance battery

VIF

Variance inflation factor

WHO

World health organization

Author contributions

All authors contributed to the study conception and design. Data collection was carried out by Haijun Zhao, Jiacheng Dong, Ping Yang, YinXia Li and Zhe Jin. Data analysis and interpretation were performed by Zhen Wu, Yiyng Yang, Lulu Xiao and Yan Dong. The initial manuscript draft was prepared by Zhen Wu, Yan Dong and Linlin Hu. Finally, Linlin Hu and Yan Dong coordinated manuscript proofreading and formatting. All authors approved the final version for submission.

Funding

This work was supported by the 2025 Lianyungang Science & Technology Program (Project: Clinical Application of Foreign-Expert-Guided Integrated Care for Older People in the Department of Geriatrics; Grant No. WZ2501); the 2025 National Standardization Pilot Project (Health and Wellness Field) (Project: Standardization Pilot Project for Integrated Elderly Care at the First People’s Hospital of Lianyungang, Jiangsu Province; Grant No. 2025203-WJ-32); the 2023 Lianyungang Health Science and Technology Project (Project: A prospective randomized controlled study on improving the comprehensive assessment of frail elderly people based on a national multi-center integrated elderly care pilot; Grant No. 202307); the Pilot Project of WHO Integrated Care for Older People in China (National Multi-center Medical and Nursing Integrated Care Pilot); and the Key Project of the National Natural Science Foundation of China (Grant No. 72034005).

Data availability

The datasets generated during this study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study complies with the Declaration of Helsinki. The study protocol (“Clinical Application of Integrated Care for the Elderly People in Geriatrics and Guidance for the Establishment of a Continuous Elderly Care Service System” Grant No. QT-20221118001-02) was reviewed and approved by the Medical Ethics Committee of The First People’s Hospital of Lianyungang on December 9, 2022. Written informed consent was obtained from all participants prior to enrollment.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.