Ecological effects in multi-level studies

T. A Blakely
<span title="2000-05-01">2000</span> <i title="BMJ"> <a target="_blank" rel="noopener" href="" style="color: black;">Journal of Epidemiology and Community Health</a> </i> &nbsp;
Multi-level research that attempts to describe ecological eVects in themselves (for example, the eVect on individual health from living in deprived communities), while also including individual level effects (for example, the eVect of personal socioeconomic disadvantage), is now prominent in research on the socioeconomic determinants of health and disease. Such research often involves the application of advanced statistical multi-level methods. It is hypothesised that such research is at risk
more &raquo; ... reaching beyond an epidemiological understanding of what constitutes an ecological eVect, and what sources of error may be influencing any observed ecological eVect. This paper aims to present such an epidemiological understanding. Three basic types of ecological eVect are described: a direct cross level eVect (for example, living in a deprived community directly aVects individual personal health), cross level eVect modification (for example, living in a deprived community modifies the eVect of individual socioeconomic status on individual health), and an indirect cross level eVect (for example, living in a deprived community increases the risk of smoking, which in turn aVects individual health). Sources of error and weaknesses in study design that may aVect estimates of ecological eVects include: a lack of variation in the ecological exposure (and health outcome) in the available data; not allowing for intraclass correlation; selection bias; confounding at both the ecological and individual level; misclassification of variables; misclassification of units of analysis and assignment of individuals to those units; model mis-specification; and multicollinearity. Identification of ecological eVects requires the minimisation of these sources of error, and a study design that captures suYcient variation in the ecological exposure of interest.
<span class="external-identifiers"> <a target="_blank" rel="external noopener noreferrer" href="">doi:10.1136/jech.54.5.367</a> <a target="_blank" rel="external noopener" href="">pmid:10814658</a> <a target="_blank" rel="external noopener" href="">pmcid:PMC1731678</a> <a target="_blank" rel="external noopener" href="">fatcat:vanzushxevfxxlexmyk4o4fy74</a> </span>
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