Life course models for upper aero-digestive tract cancer.

Upper aero-digestive tract (UADT) cancers are collectively cancers of various human body sites, such as the oral cavity, pharynx, oesophagus and larynx. Worldwide, they are the fourth most frequent cancer type and the fourth most common cause of mortality from cancer. Many studies have shown that several chronic diseases, such as cancer, which occur more commonly in later adulthood, are influenced by social and psychological circumstances during birth, childhood, adolescence and early adult life. It is suggested that the build up of problematic circumstances throughout life is the cause of disease, rather than circumstances that happen at one point in time. UADT cancer is a chronic disease of complex multifactorial origin and most of the underlying exposures/risks cannot be considered as individual factors or in isolation, as they act at different levels, which differ from time to time. Thus, life-course epidemiology, rather than drawing false dichotomies between different risk factors of the underlying disease, attempts to integrate biological and social risk processes that cause the chronic disease. It studies how socially patterned exposures during all stages of life--childhood, adolescence and early adult--influence disease risk in adulthood and socio-economic position and hence may account for social inequalities in adult health and mortality. Furthermore, varying health effects, according to the timing or duration of exposure to socio-economic circumstances, may indicate important traces to the causes of cancer. In this paper, we have attempted to draw a conceptual framework on the relationships between socio-economic inequalities, oral health risk factors along the life-course of an individual and incidence of UADT cancer.