Dietary variety and the relationship between polypharmacy and incident disability among Japanese community-dwelling older adults: A longitudinal study

Objectives: This study examined the association between polypharmacy and incident disability across the dietary variety score (DVS) strata among community-dwelling older adults.

Study design: A prospective cohort study with community-dwelling adults aged ≥65 in Aichi, Japan.

Main outcome measures: Polypharmacy was defined as ≥5 concomitant prescription drugs per day. Participants were classified as having non-polypharmacy or polypharmacy and a lower, moderate, or high DVS. Cox proportional hazard regression models were used to estimate hazard ratios (HRs) with 95 % confidence intervals (CIs) for incident disability among the polypharmacy groups after adjusting for potentially confounding variables.

Results: The analysis included 5254 older adults (55.7 % female; average age 74.0 ± 5.5 years) with a mean follow-up time of 34.7 ± 5.9 months. Among them, 4842 remained disability-free, while 412 (7.8 %) developed a disability during follow-up. The potential confounder-adjusted disability HR for participants in the polypharmacy group was 1.37 (CI: 1.07-1.75; p = 0.011). In the stratified analyses, polypharmacy in the lower DVS group was significantly associated with higher HRs for incident disability (1.62 [1.11-2.37; p = 0.013]), and no significant association between polypharmacy and incident disability was observed in the higher DVS group (1.12 [0.74-1.71; p = 0.590]).

Conclusions: Polypharmacy was positively associated with disability incidence, with a more pronounced effect in participants with a lower DVS. Polypharmacy patients may have different reasons for not being able to have a higher variety diet from non-polypharmacy people.