Fermented Dairy Food Intake and Risk of Depression and Dementia in Later Life: Findings from a Prospective Cohort of Older Australians

Background: Fermented dairy foods, such as yogurt and cheese, contain bioactive components that differ from those in non-dairy foods, but their associations with depression and dementia risk in later life remain unclear. Methods: We analyzed data from the Sydney Memory and Ageing Study, a community-dwelling cohort of adults aged 70–90 years, to examine associations between dairy intake and depressive symptoms (Geriatric Depression Scale-15), psychological distress (Kessler-10), and incident depression (physician diagnosis or antidepressant use) and dementia (DSM-IV criteria). Intake of yogurt, cheese, and non-fermented milk was assessed at baseline using a validated food-frequency questionnaire. Longitudinal associations were examined using Fine–Gray competing-risks models that accounted for death; cross-sectional associations were also assessed. Results: Among 966 participants (mean age: 78.3; 55.5% women), compared with no consumption, higher yogurt intake (one standard serving) was significantly associated with lower depressive symptom scores (adjusted β: −0.37 and −0.39 for quartiles 3–4 (mean: 88.5–164 g/day), and so was low-fat cheese intake (mean: 13.2 g/day) (adjusted β: −0.35). Over a mean follow-up of 3.3 years, 120 incident cases of depression and 68 deaths occurred: higher yogurt intake and low-fat cheese consumption (versus non-consumption) were associated with lower risk of depression (adjusted subdistribution hazard ratios 0.41 [95% CI 0.19–0.88] and 0.40 [0.21–0.78], respectively). No significant associations were observed for psychological distress, cognition, or incident dementia (a mean follow-up of 5.2 years, 100 incident cases, and 153 deaths); no associations were observed for regular cheese or milk intake. Conclusions: These findings suggest a potential role for fermented dairy foods, particularly yogurt and low-fat cheese intake, but not non-fermented milk, in mental well-being in later life.