Galea and Link respond to "Pathologies of social epidemiology," "Social epidemiology and scientific realism," and "Off-roading with social epidemiology"

Advancing the Social Epidemiology Mission of the American Journal of Epidemiology

Social epidemiology is concerned with how social forces influence population health. Rather than focusing on a single disease (as in cancer or cardiovascular epidemiology) or a single type of exposure (e.g., nutritional epidemiology), social epidemiology encompasses all the social and economic determinants of health, both historical and contemporary. These include features of social and physical environments, the network of relationships in a society, and the institutions, politics, policies, norms and cultures that shape all of these forces. This commentary presents the perspective of several editors at the Journal with expertise in social epidemiology. We articulate our thinking to encourage submissions to the Journal that: 1) expand knowledge of emerging and underresearched social determinants of population health; 2) advance new empirical evidence on the determinants of health inequities and solutions to advance health equity; 3) generate evidence to inform the translation of research on social determinants of health into public health impact; 4) contribute to innovation in methods to improve the rigor and relevance of social epidemiology; and 5) encourage critical self-reflection on the direction, challenges, successes, and failures of the field.

Stochastic mediation contrasts in epidemiologic research: interpregnancy interval and the educational disparity in preterm delivery

Low maternal education is consistently associated with increased risk of preterm delivery (PTD). The interpregnancy interval (IPI), defined as the time between the date of a previous birth and the conception date of the index pregnancy, may mediate this relationship. We estimated controlled direct effects to assess whether hypothetical interventions designed to increase IPIs would reduce the educational disparity in PTD. We introduce a technique for estimating controlled direct effects under interventions that set only some persons in the population to a specific mediator value. We used data from 847,618 singleton livebirths occurring in Quebec, Canada, between 1989 and 2010. Compared with mothers with some university education (≥14 years), mothers with less than high school (<11 years), high school (11 years), and some college (12-13 years) had excess PTD risks of 2.6% (95% confidence interval (CI): 2.4, 2.8), 1.5% (95% CI: 1.4, 1.7), and 1.0% (95% CI: 0.9, 1.1), respectively. Risk differences under an intervention corresponding to the Healthy People 2020 objective of reducing the number of mothers with IPIs less than 18 months by 3% were no different from those for the total relationship. Our results suggest that interventions designed to increase the length of short IPIs will yield no important change in the PTD disparity by maternal educational level.