This paper discusses the complex epidemiological challenges that an aging population, such as exists in the United States presents. The author states that aging populations present epidemiological challenges because of multiple arrays of time-varying risk and protective factors; multiple morbidities and functional outcomes; latency periods, among others. Life course epidemiology is a useful tool for navigating public health policy development because it integrates methodologies from numerous disciplines, including biology, medicine, social and political sciences, and public health. Life course epidemiology is particularly suited to answering the question: "What actions…need to be taken at what age across the life span of individuals to prevent disease and enhance health?"

Fundamental questions with important implications for the field of life course epidemiology are discussed, including:

• How should interrelated measures, such as weight, height and activity, which are intercorrelated, be examined and understood?
• Under what circumstances do these and other physical measures at a given age combine with other age-related factors to lead to better health?
• What is the contribution of socioeconomic factors to various measures of health, and how can relationships between health and socioeconomic status, which continuously influence each other, be understood?
• Is the one-risk factor one-outcome model still useful, given that risk factors and morbidities are often clustered and accumulate in a causal cascade?
• How can developmental and aging processes be investigated cumulatively?

The author states that comprehensive contextual descriptions to accompany data on complex causal systems are necessary and must replace classic risk-factor or variable-based approaches. The life course framework is ideally suited to achieve disease prevention because of the "richness of life span data and the long view" it provides.