A pattern of decline emerged
Older adults who started with more deficits in intrinsic capacity were more likely to follow less favorable paths of everyday function over the next 10 years, a Chinese cohort analysis found. After researchers adjusted for other factors in their models, each one-unit increase in the baseline deficit score was associated with higher odds of belonging to the high-and-declining BADL group, with an odds ratio of 1.22. The corresponding odds ratios were 1.94 for the medium-and-severely declining IADL group and 1.37 for the high-and-moderately declining group. These figures describe relative group membership, not proof that the deficits caused the decline.
The study tracked two related measures. Basic activities of daily living, or BADL, used six items scored from 0 to 6; instrumental activities of daily living, or IADL, used eight items scored from 0 to 8. Higher scores represented better function. Intrinsic capacity was represented at baseline by six binary-coded domains added into a deficit score from 0 to 6, with higher scores indicating greater impairment.
The decade produced several different paths
Researchers used the 2008-2018 waves of the nationally representative Chinese Longitudinal Healthy Longevity Survey. The primary analysis included 2,045 people aged 60 or older with complete baseline and follow-up data, just 14.0% of the 14,658 participants eligible at baseline. Group-based trajectory modeling identified clusters of people whose scores changed in similar ways, followed by models testing the association between baseline deficit scores and trajectory membership.
The BADL results split into two broad paths: 81.9% were in a high-and-stable group and 18.1% in a high-and-declining group. IADL showed three paths, with 45.7% in a high-and-mildly declining group, 41.3% in a high-and-moderately declining group and 13.0% in a medium-and-severely declining group.
Age-stratified analysis showed that 89.6% of adults aged 60 to 79 were in the high-and-stable BADL group, compared with 44.1% of those aged 80 and older. The older group also began with lower IADL scores and had faster IADL decline and a greater annual IADL decline.
The clearest signal was also the smallest
The annual BADL difference associated with baseline intrinsic capacity was small on the study's scale. For every one-point higher deficit score, the estimated BADL decline was an additional 0.007 points per year, with a 95% confidence interval from -0.010 to -0.003. Over 10 years, that amounts to about 0.07 points on the 0-to-6 BADL scale.
The comparable IADL rate estimate was -0.009 points per year for each one-point increase in the deficit score, but its 95% confidence interval ran from -0.021 to 0.002 and the result was not statistically significant. In other words, the trajectory grouping showed an association between baseline deficits and IADL group membership, but the primary model did not establish a clear deficit-by-time association for IADL.
Missing follow-up changed the picture
Follow-up assumptions changed the estimated size of the problem. Sensitivity analyses included people with at least two measurements, used multiple imputation, and tested scenarios that shifted missing values downward by 0.5 or 1.0 points. When incomplete follow-up was included, the estimated high-and-declining BADL group rose from 18.1% to 28.1%, while the medium-and-severely declining IADL group rose from 13.0% to 25.3%.
The BADL deficit-by-time association remained statistically significant under the missing-data adjustments. The IADL estimate was less stable: it changed from -0.009 points per year in complete cases to +0.050 under the one-point downward scenario. The annual IADL estimate therefore depended on the assumptions used for missing follow-up data.
A separate sensitivity analysis using continuous versions of some measures supported the BADL pattern, while none of the corresponding IADL interactions was statistically significant.
Because this was an observational secondary analysis, differences between people that were not fully measured could still have influenced the results. The findings support statistical associations among the complete-case participants, not a direct causal effect of intrinsic-capacity deficits on functional decline.
Paper data and sources
Original title: Association between intrinsic capacity and trajectories of physical function among older adults: findings from a 10-year longitudinal cohort study
Authors: Leng P, Lei Y, Wang L et al.
Journal/Repository: Frontiers in public health
Status: Peer-reviewed
First online: 2026-10-08
DOI: Not available
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