Intrinsic Capacity, Resilience, and Meaning in Life in Community-Dwelling Midlife and Older Adults

Taiwan is rapidly transitioning into a super-aged society, making healthy aging an important priority in public health and gerontological care. The World Health Organization has proposed intrinsic capacity as a framework for understanding an individual's overall physical and mental capacities. Intrinsic capacity has increasingly been used in aging research to understand subsequent functioning, functional ability, and health trajectories. Meaning in life and resilience have also been identified as important psychosocial resources in later life. However, longitudinal evidence remains limited regarding how intrinsic capacity is associated with meaning in life among community-dwelling middle-aged and older adults, particularly in community-based settings. This study is a prospective observational mixed-methods study with a quantitative cohort panel design as the main component and an embedded qualitative interview component. Community-dwelling adults aged 55 years and older who participate in programs at collaborating community centers in Taiwan will be enrolled and followed from entry into the current community center program to program completion. The follow-up assessment is expected to occur approximately 3 to 6 months after baseline, depending on each center's routine program schedule. This is a non-interventional study. The research team will not assign, alter, or standardize any treatment, activity, or service, and participants will continue their usual participation in community center programs, daily life activities, and routine care, as applicable. Quantitative data will be collected at baseline and follow-up using structured assessments. These assessments will evaluate intrinsic capacity, resilience, meaning in life, and functional characteristics such as mobility and physical performance. Sociodemographic and health-related background information will also be collected to describe the study sample and to support descriptive and supplementary analyses. Data collection will include questionnaire-based measures and brief in-person physical performance assessments administered by trained research personnel using standardized procedures. Intrinsic capacity will be assessed using the Integrated Care for Older People (ICOPE) function assessment tool adapted by the Health Promotion Administration in Taiwan. Each of the six intrinsic capacity domains will be converted into a binary score, with 1 indicating preserved or normal capacity and 0 indicating impairment or the need for further assessment according to predefined operational criteria. The six unweighted domain scores will then be summed to generate an overall intrinsic capacity score ranging from 0 to 6. Higher scores indicate better preservation of intrinsic capacity, whereas lower scores indicate a greater number of domains with impairment or concern. Because intrinsic capacity is conceptualized as a formative, multidomain construct rather than as a single reflective psychological scale, internal consistency indices will not be used as the primary basis for evaluating the overall intrinsic capacity score. Instead, interpretation of the score will rely on the operational definition of each domain, the measurement properties of the underlying tools, and clinical judgment. Meaning in life will be assessed using the Traditional Chinese version of the Meaning in Life Questionnaire, which includes the two dimensions of presence of meaning and search for meaning. Resilience will be assessed using the Chinese version of the Brief Resilience Scale. Additional physical function measures will include the Short Physical Performance Battery (SPPB), the 25-item Geriatric Locomotive Function Scale (GLFS-25), the two-step test, and handgrip strength. These measures will be used to further characterize physical functioning and to complement the assessment of locomotion-related aspects of intrinsic capacity. Reliability indices will be examined for reflective questionnaire-based scales when applicable. The longitudinal structure of the panel design is intended to capture within-person change over time and to examine whether variation in intrinsic capacity is associated with variation in meaning in life across the two assessment points. Quantitative analyses will first include descriptive statistics for participant characteristics and study variables at each time point. Categorical data will be summarized using frequencies and percentages. Continuous data will be summarized using means and standard deviations when approximately normally distributed, and medians, interquartile ranges, and ranges when distributions are skewed. Distributional characteristics, including normality, skewness, kurtosis, and potential outliers, will be examined before inferential analyses. Changes in major study variables between baseline and follow-up will be examined using paired statistical methods appropriate to the scale and distribution of the data. Change scores will be calculated as follow-up minus baseline. For approximately normally distributed continuous change scores, paired-sample t tests will be used. If the distribution of change scores is markedly non-normal, nonparametric paired methods such as the Wilcoxon signed-rank test will be considered. Effect sizes and confidence intervals will be reported when appropriate to support interpretation of the magnitude and precision of observed changes. Associations among intrinsic capacity, resilience, and meaning in life will be examined using correlation analyses and regression-based models. Pearson correlation coefficients will be used for approximately normally distributed continuous variables; Spearman rank correlations may be used when assumptions for Pearson correlations are not met. Regression models will be used to estimate the magnitude and direction of the association between intrinsic capacity and meaning in life. Depending on the final analytic specification and data completeness, models may examine baseline scores, follow-up scores, or change scores. Baseline values and relevant demographic or health-related variables may be considered in supplementary models when theoretically or clinically justified, but sociodemographic information is not specified as a main study variable in the hypothesis framework. Because the study is observational, the temporal ordering of measurements may support examination of associations over time, but the design is not intended to establish causal effects. To further examine the hypothesized pathway linking intrinsic capacity and meaning in life, mediation analysis will be conducted with resilience specified as a potential mediator. Mediation analysis using the PROCESS macro for SPSS, Model 4, will be used to evaluate whether the observed association between intrinsic capacity and meaning in life may be partly explained through resilience as an intervening psychological factor. Bootstrap resampling with 5,000 samples and 95% confidence intervals will be used to assess the indirect effect. The total effect, direct effect, and indirect effect will be reported as appropriate. In keeping with the observational nature of the study, mediation findings will be interpreted as evidence regarding possible explanatory pathways within the observed data structure rather than as proof of causal mediation. Missing data and attrition between baseline and follow-up will be examined descriptively. The number of participants with available data for each measure and each analysis will be reported. The extent and pattern of missingness will be reviewed before final analysis. Depending on the amount and likely mechanism of missing data, analyses may use complete-case methods, available-case methods, or other appropriate approaches consistent with the final statistical analysis plan. In addition to the ICOPE-based intrinsic capacity assessment, exploratory analyses will compare the SPPB, GLFS-25, and two-step test to better understand how the locomotion domain of intrinsic capacity is reflected by different mobility measures. The SPPB provides an objective summary of lower-extremity performance, the GLFS-25 captures self-reported locomotive difficulties in daily life, and the two-step test provides an additional performance-based indicator of locomotive capacity. These analyses are intended to examine which measures may be more sensitive to variation or change in the locomotion-related domain of intrinsic capacity in community-dwelling middle-aged and older adults. To complement the quantitative results, a purposively selected subsample of participants will be invited at follow-up to participate in semi-structured qualitative interviews. The qualitative component is embedded within the overall observational study and is intended to enrich and contextualize the observed quantitative associations by providing deeper insight into participants' subjective experiences of intrinsic capacity, resilience, and meaning in life.