Cancer is the second leading cause of death among U.S. adults, accounting for approximately one-fourth of all deaths in recent years (1
). Of 1.5 million estimated new cases of cancer in 2009, 24% will be breast, colorectal, and cervical cancers (2
), the three cancers for which broad consensus exists for population screening (3
). Yet, there remains a gap between actual and ideal rates of routine screening for these cancers in the U.S., particularly for colorectal cancer (CRCS) (5
). Low rates are especially troublesome for populations of lower socioeconomic status (SES) because they experience disproportionate cancer incidence and mortality (5
Socioeconomic status, widely defined as the social and economic standing of an individual within a hierarchically-stratified society, has consistently been associated with cancer screening rates: low-income, less educated and working class populations are less likely to have obtained and maintained cancer screening than their counterparts (6
). Although widely referred to as “health disparities,” we embrace the principle of distributive justice (12
) and its underlying tenet that disparities in health between the advantaged and disadvantaged are unnecessary, unjust, and avoidable (13
), by referring to these SES differentials as social inequities in health. The consistent findings regarding cancer inequities have led to numerous programmatic responses, including educational interventions aiming to reduce SES-associated inequities in knowledge and attitudes and publicly-funded programs providing screening to low-income and uninsured individuals (14
SES inequities in cancer incidence, mortality, and screening, have persisted despite decades of research and interventions targeting individuals (7
). Because cancer screening requires interaction with both healthcare services and the larger environment in which those services exist, those seeking to understand and positively influence these behaviors have increasingly turned to multilevel or contextual frameworks (21
). These frameworks move beyond the individual and conceptualize health and health behaviors as a product of the dynamic interrelation of multiple levels of influence, including the individual, community, social, and structural. For example, multilevel or “ecosocial” (25
) theories, such as neighborhood social disorganization (26
) and social capital (27
) and those models currently developing in cardiovascular and glycemic disease (28
) hypothesize about the direct and indirect effects of social and contextual influences as measured by variables such as neighborhood disorder, social cohesiveness, residential mobility, area-level poverty, or the availability of parks and recreational facilities. In contrast, individual-level frameworks conceptualize health behaviors and medical outcomes as products of such individual-level attributes as knowledge, attitudes, or genetics. By facilitating a clearer understanding of the pathways and mechanisms linking geographic areas and health, multilevel frameworks offer the promise of new and innovative interventions and policies to increase cancer screening and reduce cancer-related inequities.
A growing number of studies have used multilevel frameworks to examine the association of area-level SES—the economic, educational, occupational, or class status of a particular area— and cancer screening. Several studies have demonstrated relations between areas characterized as low in SES and a greater likelihood of late- or no- screening, even after controlling for the contribution of individual SES (23
). Not all of the measured area-based socioeconomic measures (ABSMs) have been significantly associated with screening (23
); in other studies, significant associations have become non-significant following adjustment for individual SES (39
). Moreover, at least one study found no variation in cancer screening at the area-level (42
Conceptual and methodologic differences in this literature may be responsible for the observed variation in findings. Moreover, these differences may limit comparability across studies, hinder interpretation of observed associations between area-level SES exposures and cancer outcomes, and constrain our ability to develop and test hypotheses about potential mechanisms linking neighborhoods, screening behaviors, and cancer outcomes.
To provide coherence to this emerging and heterogeneous research area, we conducted a systematic review to describe studies of area SES and individual cancer screening behaviors. Specific aims were to: 1) describe the study designs, constructs, methods, and measures; 2) describe the independent association of area socioeconomic status (SES) and cancer screening over and above individual SES; and 3) identify neglected areas of research. While common methodologic practice in the systematic review literature is to pool results from homogenous groups of high quality studies in order to synthesize the literature and draw conclusions regarding the strength of the association of interest using a narrative best evidence synthesis framework (43
) or quantitative meta analytic techniques (44
) the high degree of observed heterogeneity in these studies precluded our ability to summarize and draw definitive conclusions about the underlying association of interest. We do, however, outline a summary of the tested associations and their outcomes in the literature to date in the results section and leverage both the identified sources of heterogeneity and neglected areas of research as a basis for our discussion, in which we identify the key priority areas needing refinement in the multilevel cancer screening literature.