Complex multimorbidity and mortality in Japan: a prospective propensity-matched cohort study

Area of Science:

• Gerontology
• Epidemiology
• Public Health

Background:

• Defining multimorbidity (MM) solely by disease count has limitations.
• Complex multimorbidity (CMM) considers the number of affected body systems, offering a nuanced approach.
• Understanding predictors of mortality in aging populations is crucial.

Purpose of the Study:

• To compare the predictive accuracy of CMM versus conventional MM for mortality in older Japanese adults.
• To investigate the association between CMM and mortality in a large, prospective cohort.
• To evaluate the utility of a body system-based definition of multimorbidity.

Main Methods:

• A population-based prospective cohort study (Japan Gerontological Evaluation Study, 2010-2016).
• Included functionally independent individuals aged 65+ with complete illness data.
• CMM defined as ≥3 body system disorders; propensity score matching used to compare mortality between CMM and MM groups.

Main Results:

• The study followed 38,889 older adults for 6 years.
• Both MM (HR 1.07) and CMM (HR 1.07) were associated with increased mortality.
• The association between CMM and mortality was not statistically significant (p=0.08), unlike conventional MM (p=0.02).

Conclusions:

• This is the first study on CMM and mortality in older Japanese adults.
• MM and CMM demonstrate similar predictive power for mortality in this cohort.
• Further validation in larger, diverse populations is recommended to confirm these findings.