The moderating effect of dietary fiber and protein on the relationship between symptoms of depression and anxiety and cognitive decline.

INTRODUCTION: Depression and anxiety often co-occur with Alzheimer's disease, exacerbating the associated cognitive impairment. This study examined moderating effects of dietary protein and fiber intake on relationships between depressive and anxiety symptoms, and cognitive decline. METHODS: Cognitively unimpaired (n = 553; 39.4% male, 70.6 ± 9.6 years) provided baseline fiber and protein intake, and had repeated cognitive testing and symptoms of depression/anxiety measured (baseline and up to eight follow-ups over 144 months). Moderation and simple slope analyses were employed in the cohort as a whole and following stratification by sex. RESULTS: Fiber intake moderated the relationship between change in depressive symptoms and decline in language (β = -0.005, p < 0.001) and Preclinical Alzheimer Cognitive Composite (PACC); scores (β = -0.003, p = 0.010). In males, fiber intake moderated the relationship between change in anxiety symptoms and executive function decline (β = -0.003, p = 0.018), with protein intake moderating change in depressive symptoms and decline in attention (β = 0.006, p = 0.011). DISCUSSION: Adequate dietary fiber and protein intake moderated association between depressive and anxiety symptoms and cognitive decline, supporting their potential role within multidomain strategies aimed at maintaining cognitive health in older adults.