Cities and health: an evolving global conversation

'Multiple causation' is the canon of contemporary epidemiology, and its metaphor and model is the 'web of causation.' First articulated in a 1960 U.S. epidemiology textbook, the 'web' remains a widely accepted but poorly elaborated model, reflecting in part the contemporary stress on epidemiologic methods over epidemiologic theories of disease causation. This essay discusses the origins, features, and problems of the 'web,' including its hidden reliance upon the framework of biomedical individualism to guide the choice of factors incorporated in the 'web.' Posing the question of the whereabouts of the putative 'spider,' the author examines several contemporary approaches to epidemiologic theory, including those which stress biological evolution and adaptation and those which emphasize the social production of disease. To better integrate biologic and social understandings of current and changing population patterns of health and disease, the essay proposes an ecosocial framework for developing epidemiologic theory. Features of this alternative approach are discussed, a preliminary image is offered, and debate is encouraged.

Land-use and transport policies contribute to worldwide epidemics of injuries and non-communicable diseases through traffic exposure, noise, air pollution, social isolation, low physical activity, and sedentary behaviours. Motorised transport is a major cause of the greenhouse gas emissions that are threatening human health. Urban and transport planning and urban design policies in many cities do not reflect the accumulating evidence that, if policies would take health effects into account, they could benefit a wide range of common health problems. Enhanced research translation to increase the influence of health research on urban and transport planning decisions could address many global health problems. This paper illustrates the potential for such change by presenting conceptual models and case studies of research translation applied to urban and transport planning and urban design. The primary recommendation of this paper is for cities to actively pursue compact and mixed-use urban designs that encourage a transport modal shift away from private motor vehicles towards walking, cycling, and public transport. This Series concludes by urging a systematic approach to city design to enhance health and sustainability through active transport and a move towards new urban mobility. Such an approach promises to be a powerful strategy for improvements in population health on a permanent basis.