Dietary Factors and Risk of Late-Life Depression: Findings from a Swedish Population-Based Cohort Study

Although diet is increasingly implicated in depression prevention, prospective evidence remains scarce with respect to which food groups and nutrients influence depression onset in later life. We sought to examine associations between 15 dietary factors and incident depression among older adults. Data were obtained from the Swedish National study on Aging and Care in Kungsholmen (SNAC-K), with up to 15 years of follow-up among community-dwelling adults aged ≥ 60 years and free of depression at baseline. Dietary exposures (food groups and nutrients), harmonized with Global Burden of Disease (GBD) study definitions, were assessed three times over the first 6 years using a validated 98-item food frequency questionnaire. We also examined an overall dietary risk score reflecting the number of GBD recommendations not met. Onset of major or minor depression were identified through physician-administered interviews based on DSM-IV-TR criteria, and depressive symptom severity was assessed with the Montgomery–Åsberg Depression Rating Scale. Associations between dietary exposures and incident forms of depression were estimated using Cox proportional hazards models adjusted for sociodemographic, lifestyle, and health-related covariates. Among 2148 participants with available data at follow-up (mean age 71.3 ± 9.3 years, 61.4% females), higher whole-grain consumption (per 30 g/day; HR = 0.63, 95% CI: 0.43–0.91) and total dietary fiber intake (per 5 g/day; HR = 0.69, 95% CI: 0.52–0.91) were associated with lower risk of major depression. Fruit consumption was inversely associated with minor depression (per 100 g/day; HR = 0.81, 95% CI: 0.67–0.97) and mild-to-moderate depressive symptoms (HR = 0.87, 95% CI: 0.76–0.99). Further, higher consumption of vegetables (per 100 g/day; HR = 0.86, 95% CI: 0.74–1.00) was linked with reduced risk of mild-to-moderate depressive symptoms. When considering overall dietary risk, higher scores were associated with increased incidence of major depression and mild-to-moderate symptoms. Some associations differed by sex, age, and body mass index, although most interactions were not statistically significant. Specific dietary components, alongside overall diet quality, may represent preventive targets for late-life depression at the population level and inform more tailored dietary strategies.