[Developmental origins of adult health and disease: an important concept for social inequalities in health].

According to the theory of the developmental origins of adult health and disease, development in utero and in the first years of life are critical phases during which susceptibility to many chronic diseases is set. Diseases eventually occur only if the environment and lifestyle in later life is favorable. Exposure to chemicals (environmental or drug), to infectious agents, unbalanced nutrition, or psychosocial stress prenatally or in the first months/years of life are all factors which have been shown to impact long-term health of individuals. The consequences, however, are not limited to health. A demonstrative example was provided by the study of the influenza epidemic of 1918-1919 in the United States. Nationwide, it was estimated that the loss of income over a lifetime for individuals exposed during fetal life to this epidemic amounted to 14 billion dollars. This example demonstrates that an exposure during fetal life, which is not socially differentiated, may affect the social situation of individuals in adulthood. In many situations, it is much more difficult to separate the specific effect of a given exposure from the overall effect of the social environment. Indeed, it has been shown that socioeconomic status in childhood is associated with increased risk of mortality in adulthood, even after accounting for the socioeconomic status and risky behaviors in adulthood. Among the explanations, the theory of developmental origins of health credits of biological plausibility the model of critical periods early in which the individual is particularly vulnerable to certain exposures. Thus, ensuring the best conditions for the biological, physical, emotional and cognitive development of children in early life will enable them to reach their potential in terms of health and socioeconomic return to society. Investment in this period also brings the hope of reducing the perpetuation of social inequalities and health from generation to generation.