The Association of Diet and Lifestyle Factors With Quality of Life and Self-Rated Health in Older Adults: The Loma Linda Longevity Study

Introduction: Subjective health predicts mortality in older adults. We examined associations of vegetarian diet, adherence duration, and a Healthy Lifestyle Index with quality of life (QoL) and self-rated health (SRH) in adults ≥75 years. Methods: We analyzed cross-sectional data from 421 Loma Linda Longevity Study participants using ordinal logistic regression. Three hierarchical models were estimated: M1 (diet + sociodemographic covariates), M2 (M1 + diet duration + Healthy Lifestyle Index), and M3 (final fully adjusted model: M2 + BMI + multimorbidity). Moderation by adherence duration (<10 vs ≥ 10 years) was tested via interaction and stratified analyses. Results: The Healthy Lifestyle Index showed strong dose-response (highest vs lowest quartile: QoL aOR = 7.24, 95% CI: 3.31-15.85; SRH aOR = 4.69, 95% CI: 2.26-9.72; both P for trend <0.001). Among long-term adherents (≥10 years), vegetarian diet was significantly associated with better SRH (aOR = 2.11, 95% CI: 1.11-4.00, P = 0.022). In the fully adjusted model, the vegetarian association attenuated to borderline significance, with multimorbidity (for both outcomes) and BMI (for SRH only) emerging as stronger independent predictors. Conclusions: An integrated healthy lifestyle shows a robust dose-response with subjective health. Long-term vegetarian adherence is independently associated with better self-rated health in adults ≥75 years.