Investigating relationships between nutrition, exercise, mood and hippocampus-dependent cognition in older adults in the Canadian Longitudinal Study on Aging

Major depressive disorder affects 5.8% of Canadians aged 15-64, contributing to mental and physical decline, and increasing the risk of death by 2-3 times. Although community dwelling older adults show lower rates of major depression, their levels of depressive symptoms are much higher than those of younger adults. There is a pressing need to investigate lifestyle factors that promote resilience against depression and healthy aging. Our past research in rodents found synergies between exercise and dietary factors in promoting stress resilience and brain health. The goal of our proposed research is to translate these findings to humans. Specifically, we will examine the association between anti-oxidant and anti-inflammatory dietary factors, exercise and age-related levels of depressive symptoms and cognitive decline. This research will help inform public health recommendations for older adults to promote healthy aging and resilience to depression.

Our study investigated the potential impact of exercise, dietary and other lifestyle factors on mood and cognition. We undertook data cleaning and construction of derived variables using R programming based upon a review of the literature. Numerous predictive machine learning models (neural networks, random forests, etc.) were trained using various subsets of the data and incorporated the analytical weights. Our models revealed patterns of lifestyle, social, and physical variables predictive of major depressive disorder, mood, and cognitive test performance. Although diet and exercise were relevant to mood, we discovered that household income and lung function were more strongly associated with Center for Epidemiologic Studies Depression Scale (CESD-10) scores. As such, our results provide insight into the contributions of health, socioeconomic, demographic, and lifestyle patterns associated with mood and cognitive functioning in the aging Canadian population.