Multi-trajectories of intrinsic capacity and their impact on incident disability in community-dwelling older adults in Japan.

Four distinct intrinsic capacity trajectories were identified among community-dwelling older adults using group-based multi-trajectory modelling.

• The four trajectories were: preserved (60.5%), hearing-decline (15.9%), physio-psychological decline (17.5%), and global decline (6.1%).
• Trajectories spanned six IC domains: cognition, locomotion, vitality, vision, hearing, and psychological well-being.
• The analysis included 1056 disability-free community-dwelling older adults aged 65-89 years.
• Participants completed three or more surveys between waves 2-7 (2000-2012) of the National Institute for Longevity Sciences-Longitudinal Study of Aging.

During a median 9.8-year follow-up, 380 participants (36.0%) developed disabilities.

• Incident disability was confirmed through the Long-term Care Insurance System certificate.
• Maximum follow-up period was 17.5 years.
• The final assessment from the trajectory period was used as baseline for disability follow-up.
• Multivariable-adjusted cause-specific Cox proportional hazards models and Fine-Gray subdistribution hazard models were employed.

The hearing-decline trajectory group had a significantly higher risk of incident disability compared to the preserved group.

• Multivariable-adjusted hazard ratio (aHR) was 1.53 (95% CI 0.117-1.99) in the cause-specific Cox model.
• The hearing-decline group comprised 15.9% of the study population.
• Elevated risk in the hearing-decline group was observed beyond two years of follow-up in time-stratified analyses.

The physio-psychological decline trajectory group had a significantly higher risk of incident disability compared to the preserved group.

• Multivariable-adjusted hazard ratio (aHR) was 1.66 (95% CI 1.26-2.18) in the cause-specific Cox model.
• The physio-psychological decline group comprised 17.5% of the study population.
• This group showed significantly higher disability risk during both the first two years and beyond two years of follow-up in time-stratified analyses.

The global decline group's disability risk was not statistically significant in the cause-specific Cox model but became significant after accounting for the competing risk of mortality.

• Cause-specific Cox model aHR was 1.41 (95% CI 0.96-2.08), which was not statistically significant.
• Fine-Gray subdistribution hazard model aHR was 1.56 (95% CI 1.09-2.22), which was statistically significant.
• The global decline group comprised 6.1% of the study population.
• The global decline group showed significantly higher disability risk during the first two years of follow-up in time-stratified analyses.

Time-stratified analyses revealed differential temporal patterns of disability risk across IC trajectory groups.

• During the first two years of follow-up, the physio-psychological decline group and global decline group exhibited significantly higher risks of incident disability.
• Beyond two years of follow-up, elevated risks were observed in the hearing-decline group and physio-psychological decline group.
• The hearing-decline group did not show significantly elevated early (within two years) disability risk.
• These differential patterns highlight time-varying relationships between IC trajectory patterns and disability onset.

The WHO intrinsic capacity framework spans six domains that were each tracked as separate trajectory components.

• The six domains assessed were: cognition, locomotion, vitality, vision, hearing, and psychological well-being.
• Group-based multi-trajectory modelling was used to simultaneously model trajectories across all six domains.
• Surveys spanned from 2000 to 2012 (waves 2-7), covering up to 12 years of IC trajectory data.
• The study population included community-dwelling adults aged 65-89 years who were disability-free at baseline.