Dynamic evolution of multimorbidity patterns and association with medication adherence in Chinese older adults: a longitudinal analysis using latent transition analysis and semi-Markov models

Multimorbidity is prevalent among the elderly, with long-term medication use posing increasing adherence challenges. This study examines the evolution of multimorbidity patterns and their dynamic association with medication adherence to generate empirical evidence for the design of personalized treatment strategies and targeted health interventions for older adults with multimorbidity. Using data from 2,798 elderly individuals with multimorbidity in the 2011–2020 China Health and Retirement Longitudinal Study, this study employs latent transition analysis and a semi-Markov model to assess adherence transitions across four multimorbidity patterns. Relative Transition Rates (RTRs) were used to quantify differences in adherence improvement and deterioration probabilities. The cardiovascular disease group remained relatively stable, with other patterns shifting toward it over time. Between 2013 and 2018, the incidence of adherence improvement (60.60%) was more frequent than deterioration (39.40%), especially in the multi-system disorders (62.08%) and respiratory diseases groups (67.59%), while deterioration was higher in the gastrointestinal metabolism (40.75%) and cardiovascular disease groups (39.64%). Compared to the multi-system disorders group, the gastrointestinal metabolism group was less likely to improve from low to moderate adherence (RTR = 0.63, 95% CI: 0.41–0.98), while both the gastrointestinal metabolism (RTR = 4.45, 95% CI: 1.92–10.18) and cardiovascular disease groups (RTR = 2.57, 95% CI: 1.07–6.11) had higher risks of declining from high to moderate adherence. Cardiovascular diseases appear increasingly central in elderly multimorbidity, with gastrointestinal metabolism and respiratory conditions potentially serving as early or coexisting risk factors. Early cardiovascular risk monitoring may be beneficial in these groups, while long-term adherence support remains important for gastrointestinal and cardiovascular patterns.