Table 1 Conceptual and methodological issues raised in published reports on area effects on health
Conceptual and methodological challengesDescription
Conceptualising causal pathways210Absence of fully articulated theoretical frameworks and formulation of testable hypotheses.
Designating the ecologic unit of analysis1 11 12Ecologic units of analysis have been referred to as neighbourhood, small area, local area, and place. These labels have been used interchangeably without concern for differences in conceptual and operational definitions even though some have argued that there are substantive reasons for appropriately defining the nature of the ecological unit of analysis.
Defining the spatial contours of the ecological unit of analysis1 5 8 13Spatial contours of small areas are mostly delimited by existing administrative and statistical spatial units. However, these areas may be of limited value in examining the association between area level exposures and health outcomes, because they may lack any intrinsic meaning in relation to health, they may not correspond to the spatial distribution of environmental features (ecologic exposures) associated with health, and they may be inconsistent with how residents define and experience their residential area.
Defining ecologic exposures5 7 13 15 1722Little attention has been devoted to conceptually and operationally defining ecological exposures as researchers have tended to aggregate data from individuals to create meaningful area variables.
Controlling for individual-level variables2 5 13 15 18 23Lack of consistency in controlling for individual level variables and further lack of consensus on whether individual variables should be conceptualised as confounders, moderators, or mediators of the associations between ecological exposures and health outcomes.
Power, sample size, and representativeness5 13 15 25Usual considerations surrounding statistical power and sample size have been neglected.
Use of multilevel modelling techniques4 13 15 23 24 2628Appropriate use of multilevel modelling techniques has been applied suboptimally, thus limiting novel perspectives that might ensue from their judicious application: results are mainly reported for fixed effects whereas the potentials of discussing conceptual and methodological ramifications of random effects have been ignored.
Disentangling context from composition7 8 13 18 27 2934Some investigators argue for disentangling the portion of the between area variation in health that is attributable to areas in which people live (contextual effect) from the portion attributable to individuals’ characteristics (compositional effect), whereas others argued that this is a “false” issue as context and composition are inextricably intertwined.
Dearth of longitudinal and experimental studies8 18 34 35Few studies have relied on research designs other than cross sectional. This limits ascertaining the duration and timing of ecological exposures, addressing selection bias, and ascribing causality. Furthermore, as people, areas, and the relation between the two may change over time, using longitudinal designs is of accrued importance.