[Epidemiology and social determinants of health inequalities].

BACKGROUND: The general approach of social epidemiology is based on the observation of a strong social stratification of health outcomes within populations: a similar stratification of factors associated with health must therefore also exist according to social status. To explain social differences in health, the natural approach for epidemiologists is to consider an imbalanced distribution of established risk factors according to the social position of individuals. As this approach has largely failed, two main other research areas were recently explored: (i) identification of "new" social risk factors; (ii) research of possible mechanisms of social differences in health. METHODS AND
RESULTS: Identification of social risk factors: early events and life course, occupational factors, social relationships (social networks and support, discrimination, neighborhood characteristics), health care. Research of possible mechanisms of social differences in health in the context of specific theoretical frameworks: the materialist model, the psychosocial model and the eco-social model integrating the interaction between individuals'characteristics and their environment. COMPLEX METHODOLOGICAL PROBLEMS: definition and measurement of variables characterizing the social situation of individuals; quantification of social inequalities at population level. Observational methods must often rely on very long-lasting cohorts, and imply statistical methods that account for longitudinal data or are able to manage simultaneously individual and contextual data.