Priscilla M Lopez1, S V Subramanian2, C Mary Schooling3. 1. Department of Environmental, Occupational, and Geospatial Health Sciences, CUNY Graduate School of Public Health and Health Policy, New York, NY, USA. 2. Department of Social and Behavioral Sciences, Harvard University, Boston, MA, USA. 3. Department of Environmental, Occupational, and Geospatial Health Sciences, CUNY Graduate School of Public Health and Health Policy, New York, NY, USA; School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China. Electronic address: maryschooling@sph.cuny.edu.
Abstract
OBJECTIVES: We are often confronted in public health by associations that vary by population or subpopulation. Much effort has focused on the statistical and biological interpretation of such effect measure modification (EMM) because of the importance to public health. However, EMM remains difficult to conceptualize because it apparently violates everyday understanding of causes as usually acting consistently, making it difficult to predict when EMM may occur and raises questions about how to determine the external validity of interventions without extensive retesting by population or subpopulation. STUDY DESIGN AND SETTING: Methods exposition. RESULTS: We propose that EMM can be thought of as mediation of an intervention (or exposure) on outcome by mechanism(s) whose relevance differs between population groups, which can be illustrated in causal diagrams, that is, directed acyclic graphs and selection diagrams, meaning external validity can be formally considered as mediation according to "selection variables." EMM can then be represented graphically and its consequences predicted. CONCLUSION: This new conceptualization of EMM transforms EMM from a concept that violates everyday understanding of causes into an insight generating means of thinking about interventions (or exposures) in terms of their mediating mechanism(s) and corresponding population- or subpopulation-specific attributes to help target interventions effectively.
OBJECTIVES: We are often confronted in public health by associations that vary by population or subpopulation. Much effort has focused on the statistical and biological interpretation of such effect measure modification (EMM) because of the importance to public health. However, EMM remains difficult to conceptualize because it apparently violates everyday understanding of causes as usually acting consistently, making it difficult to predict when EMM may occur and raises questions about how to determine the external validity of interventions without extensive retesting by population or subpopulation. STUDY DESIGN AND SETTING: Methods exposition. RESULTS: We propose that EMM can be thought of as mediation of an intervention (or exposure) on outcome by mechanism(s) whose relevance differs between population groups, which can be illustrated in causal diagrams, that is, directed acyclic graphs and selection diagrams, meaning external validity can be formally considered as mediation according to "selection variables." EMM can then be represented graphically and its consequences predicted. CONCLUSION: This new conceptualization of EMM transforms EMM from a concept that violates everyday understanding of causes into an insight generating means of thinking about interventions (or exposures) in terms of their mediating mechanism(s) and corresponding population- or subpopulation-specific attributes to help target interventions effectively.
Authors: Junxi Liu; Shiu Lun Au Yeung; Man Ki Kwok; June Yue Yan Leung; Shi Lin Lin; Lai Ling Hui; Gabriel Matthew Leung; C Mary Schooling Journal: Sci Rep Date: 2019-11-14 Impact factor: 4.379
Authors: Jiao Wang; Man Ki Kwok; Shiu Lun Au Yeung; Jie Zhao; Albert Martin Li; Hugh Simon Lam; Gabriel Matthew Leung; Catherine Mary Schooling Journal: Sci Rep Date: 2020-02-21 Impact factor: 4.379
Authors: Junxi Liu; Shiu Lun Au Yeung; Man Ki Kwok; June Yue Yan Leung; Lai Ling Hui; Gabriel Matthew Leung; C Mary Schooling Journal: PLoS One Date: 2020-02-11 Impact factor: 3.240