Oral frailty and long-term changes in nutritional status and dietary behaviors in community-dwelling older adults: chronic exposure and transitions in the 12-year Kashiwa cohort study

Oral frailty may contribute to a decline in nutritional status and dietary behaviors among older adults. However, long-term evidence distinguishing stable inter-individual differences from within-person changes while also examining onset and recovery remains limited. We conducted a 12-year prospective cohort study on community-dwelling adults aged ≥ 65 years in Kashiwa, Japan. Oral frailty was assessed using the Oral Frailty 5-item Checklist. The outcomes included body mass index (BMI), Mini Nutritional Assessment–Short Form (MNA-SF) score, dietary diversity, food group intake frequency, and incident nutritional risk. Generalized linear mixed models with random intercepts were used to separate oral frailty into between- and within-person components. Transition models were used to examine oral frailty onset and recovery. Cox proportional hazards models were additionally used to examine the association between baseline oral frailty and incident nutritional risk, defined as an MNA-SF score ≤ 11. We included 1,679 participants, with a mean age of 72.9 ± 5.5 years; 49.5% were women. Higher person-specific mean oral frailty was associated with lower MNA-SF scores (β = −0.674, 95% CI − 0.815 to − 0.532) and lower dietary diversity (β = −0.502, 95% CI − 0.707 to − 0.298). Within-person worsening in oral frailty was associated with lower MNA-SF scores (β = −0.191, 95% CI − 0.278 to − 0.105), but not clearly with BMI. In the transition models, oral frailty onset was associated with lower BMI and MNA-SF scores, whereas recovery was associated with higher MNA-SF scores and dietary diversity. Among the participants without nutritional risk at baseline, baseline oral frailty was associated with incident nutritional risk during follow-up (hazard ratio 1.58, 95% CI 1.28 to 1.94). Oral frailty was longitudinally associated with nutritional status and dietary behaviors. These findings suggest that oral frailty reflects chronic nutritional vulnerability and dynamic within-person changes. Oral frailty onset was associated with poorer nutritional indicators, whereas recovery was associated with more favorable nutritional indicators. Baseline oral frailty was also associated with subsequent nutritional risk. However, the observational study design does not establish that improvement in oral frailty causes subsequent nutritional improvement.