Daniel D Reidpath is slightly misguided to observe that social inequalities in health have "not yet been elevated to the status of having its own National Library of Medicine MeSH (medical subject) heading", and his remark hence calls for some additional precision.

As a MeSH search for inequalit* will indicate, the National Library of Medicine lists "Inequality" and "Inequalities" as entry terms for its "Socioeconomic Factors" heading, which was introduced in 1968. The other MeSH entry for social factors, namely "Social Environment", does not mention inequalities in that respect. Admittedly, these headings do not allow for a clear mapping of the health inequalities literature, which is better accessed through user-submitted search strings like "health inequalit*[tw]."

Nevertheless, much more recently, and as a MeSH search for disparit* indicates, the National Library of Medicine has introduced "Health Status Disparities" in its topical indexing. The heading coverage is described as "variation in rates of disease occurrence and disabilities between socioeconomic and/or geographically defined population groups." A PubMed search on the heading already returns over 500 references, consistent with Daniel D Reidpath's view that health inequalities have become a central element of the research agenda for social epidemiologists, sociologists of health and illness, and virtually any scholar interested in health economics and welfare.

Another new heading introduced in 2008 is "Healthcare Disparities," which covers "Differences in access to or availability of facilities and services" -- a partial definition of social inequalities in health, as it is much more restrictive in scope and focuses on the single but crucial dimension of access to health services. The provision of a specific heading for inequalities in access to healthcare, however, comes with several cross-national and cross-sectoral advantages, and constitutes a valuable bibliographic tool for researchers in that respect.

What Daniel D Reidpath's comment underlines is the variety of terms associated with "social inequalities in health" in international research. In the American context, research on the differential distribution of mortality and morbidity by socio-economic status (and other social factors) is susceptible to be flagged as research on health "disparities" instead of "inequalities" or "inequities." Acknowledging another geographical bias, Paul Braveman has observed that "‘health equity’ is a term rarely encountered in the United States but more familiar to public health professionals elsewhere." [1]. In Britain, the political history of health inequalities shows that the more neutral terms "health variations" were instrumental in maintaining health inequalities on the political agenda, following governmental reluctancy towards the conclusions of the Black report [2,3].

An explanation for variations in research terminology might relate to national contexts of health politics. In the case of the United States, it would be seemingly unsurprising to observe that a nation that tolerates high levels of inequality within its population would prefer the term "disparity" to address a phenomenon otherwise addressed as "inequality", a term which would appear to be politically connoted in the American polity. Existing data on inequality and public opinion tend to reveal, however, a more complex picture, in which attitudes towards inequality exhibit less cross-national variation than policy preferences [4,5].

More generally, research on health inequalities will inevitably intersect with other forms of social research, such as racial and ethnic inequality [6]. In fact, health inequalities are shaped by a large array of factors, not all of which should not be expected to be linguistic or rhetorical like the ones mentioned here; in France, for instance, institutional factors are constraining the development of both research and policy regarding health inequalities [7,8]. Current scholarship, however, has given considerably less attention to the relationship between health inequalities and institutional variables derived from the political context.

This brief response aims not only at rectifying the slight inadequacy in Daniel D Reidpath's review, but also at showing how social inequalities in health call for interdisciplinary research perspectives in health and society, as actively promoted by the JECH. One might finally want to stress the dearth of political analysis in this field of research [9].

References

[1] Braveman, P. Health disparities and health equity: concepts and measurement. Annu Rev Public Health 2006;27:167–94.

[2] Berridge V. Blume S, eds. Poor health. Social inequality before and after the Black Report. London: Frank Cass, 2003.

[3] Macintyre S. Before and after the Black report: four fallacies. In: Berridge V. Blume S, eds. Poor health. Social inequality before and after the Black Report. London: Frank Cass, 2003:198–219.

[4] Pontusson J. Inequality and prosperity in contemporary capitalism. Ithaca, NY: Cornell University Press, 2005.

[5] McCall L, Kenworthy L. Americans' social policy preferences in the era of rising inequality. Unpublished manuscript, 2008.

[6] Gamble VN, Stone D. US policy on health inequities: the interplay of politics and research. J Health Polit Policy Law 2006;31:93–126.

[7] Berthod-Wurmser M. Programmes de recherche et débat public sur les inégalités de santé: la France est-elle en retrait ? In: Leclerc A, Fassin D, Grandjean H, et al. Les inégalités sociales de santé. Paris: La Découverte, 2000: 69–80.

[8] Briatte F. Lutter contre les inégalités de santé en France et en Grande- Bretagne. [Master's thesis]. Grenoble: Institute of Political Studies, University of Grenoble, 2006.

[9] Judge, K. Politics and health: policy design and implementation are even more neglected than political values? Eur J Pub Health 2008;18:355–356.