A substantial literature exists that demonstrates associations between putative risk factors and cognitive decline in late life. However, there is a need to integrate this broad literature within a framework that incorporates the interaction of behavioral and ecological influences with cognitive development. Such a framework is required for developing a range of personal and environmental interventions to optimize cognitive development in the population, and to reduce the risk of cognitive impairment in late life.
This review aims to identify the key considerations for developing a life course model of the various factors that influence cognitive development and cognitive decline. A contextualized, dynamic approach to life course epidemiology is proposed.
A theoretical evaluation of key methodological and interpretational issues relating to how risk factors influence cognitive development and cognitive impairment was conducted. This focused on the example of alcohol consumption as a risk factor for cognitive decline and dementia.
This review identified dimensions that need to be accounted for in life course theories of cognitive development and cognitive impairment. These include: (a) intergenerational influences; (b) methodological and interpretational issues; (c) individual differences (personal factors); (d) contextual factors (environmental or ecological factors), and (e) cognitive ability as determinant. The methodological and interpretational factors included measurement of exposure and outcome variables; the important distinction between level of ability versus change over time; nonlinear relationships among exposures and outcomes, and outcomes and age; the distinction between association and cause, and between short-term effects and long-term change.
A contextualized, dynamic approach to life course epidemiology accounts for the complex range of influences over the life course that interact to determine normal and pathological cognitive ageing. This approach provides a framework for the development of interventions to maximize cognitive gains in early life, and minimize cognitive loss in late life.