trials,1 researchers use a variety of other methods, including multivariate modeling, instrumental variables, quasi-experimental designs, Bayesian approaches to inference, natural experiments, and “connecting-the-dots” between disparate bodies of knowledge (Braveman et al., 2010a; Dow et al., 2010; Kelly et al., 2006).
Another challenge in analyzing social factors in a cross-national context is that a given factor may have different health implications depending on local circumstances. Standards of living vary across countries, as do social safety nets and other programs designed to alleviate poverty, unemployment, and homelessness. We therefore approach this topic aware of these important caveats and limitations.
Recent reviews have documented links between social factors and health, elucidated plausible causal pathways, and discussed the strength of evidence for causality (Adler and Rehkopf, 2008; Adler and Stewart, 2010; Braveman et al., 2010a, 2011b; Commission on the Social Determinants of Health, 2008; Kawachi et al., 2010). As shown in Box 6-1, among the broad types of social factors with strong and pervasive links to a wide array of important health outcomes are income (Mackenbach et al., 2005; Muennig et al., 2010; Woolf et al., 2010), accumulated wealth (Pollack et al., 2007), educational attainment (Elo and Preston, 1996; Jemal et al., 2008a; Woolf et al., 2007), occupational characteristics (An et al., 2011), and social inequality based on racial or ethnic group (Bleich et al., 2012; Marmot, 2005; Williams and Collins, 2001; Williams and Mohammed, 2009). In this section, we briefly summarize this literature.
Income and Wealth
Extensive evidence documents the association between income and mortality. Unhealthy behaviors, such as smoking, tend to be more prevalent among low-income groups. Income or wealth enables one to afford a nutritious
1The premise that randomized controlled trials are the “gold standard” for establishing causal relationships has put the accumulation of knowledge about the social determinants of health at a distinct disadvantage. It is increasingly recognized that scientifically valid studies of social factors that can answer important questions must draw on a wide variety of well-implemented research designs (Anderson and McQueen, 2009; Black, 1996; Glasgow et al., 2006; McQueen, 2009; Petticrew and Roberts, 2003; Victora et al., 2004).