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Articles: Katherine L. Frohlich and Louise Potvin Transcending the Known in Public Health Practice: The Inequality Paradox: The Population Approach and Vulnerable Populations Am J Public Health 2008; 98: 216-221 [Abstract] [Full text] [PDF]

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Increases in relative differences in adverse health outcomes do not necessarily reflect increasing h

James P. Scanlan   (24 January 2008)

Increases in relative differences in adverse health outcomes do not necessarily reflect increasing h 24 January 2008
James P. Scanlan, Attorney James P. Scanlan, Attorney at Law Send letter to journal: Re: Increases in relative differences in adverse health outcomes do not necessarily reflect increasing h jps{at}jpscanlan.com James P. Scanlan	Frohlich and Potvin [1] provide a theoretical explanation for why population-approach interventions will tend to increasingly concentrate adverse health outcomes in disadvantaged groups, thereby increasing health inequality as measured in terms of relative differences in adverse outcomes. They also cite several studies showing how certain interventions in fact led to such results. One might add to that list the study by Pickett et al. [2] that appeared here in 2005. It examined a program to educate parents as to the benefits of having infants sleep on their backs. The authors of that study expected the program to reduce socioeconomic disparities in sudden infant death syndrome (SIDS), since there would be few barriers to universal implementation of the recommendations. Nevertheless, while the program dramatically reduced SIDS rates, socioeconomic inequalities in SIDS, measured in terms of relative difference in SIDS rates, increased. But in regarding the usual consequences of population-approach interventions to be increases in health inequalities, Frohlich and Potvin overlook that, while such interventions will tend to increase relative differences in adverse outcome rates, they will tend to reduce relative differences in favorable outcome rates.[3-6] Thus, it is a mistake to regard the increase in relative differences in adverse outcome rates as necessarily reflecting increasing health inequality in any meaningful sense. The same holds with regard to beneficial health procedures, such as mammography or prenatal care. General increases in the availability of such procedures tended to reduce relative differences in rates of receipt (the favorable outcome), while increasing relative differences in failing to receive the procedures (the adverse outcome). Until recently, inequalities were typically measured in terms of relative differences in the favorable outcome and hence inequality in such procedures was usually deemed to be decreasing in a meaningful way. But such belief was no more valid than the opposite belief based on the increasing relative difference in failing to receive the procedures.[3-6] The pattern whereby relative differences in adverse and favorable outcomes tend to change in opposite directions as an adverse outcome is reduced in overall prevalence is a consequence of the fact that the proportion the disadvantaged group comprises of the part of the overall population most likely to benefit from the intervention – i.e., the part easiest for the intervention to reach – tends to be larger than the proportion the disadvantaged group comprises of the population already experiencing the favorable outcome, but smaller than the proportion it comprises of the population that will continue to experience the adverse outcome.[7] Thus, whether the disadvantaged group is disproportionately failing to benefit, or disproportionately benefiting, from an intervention is a matter of perspective. It is true that health interventions particularly targeted toward the disadvantaged can mitigate the tendency towards an increase in the relative difference in adverse outcomes, while enhancing the tendency for the intervention to reduce relative differences in favorable outcomes. Thus, such measures could reduce health inequality in a meaningful sense. But one must consider carefully the cost-effectiveness of such measures, with regard to the per-cost benefit both to the overall population and to disadvantaged groups. If at a particular cost a population-approach intervention will benefit 100 persons in the easier to reach part of the overall population of which 50 are considered disadvantaged, and a targeted intervention will benefit 50 persons in the harder to reach part of the population of which 30 are considered disadvantaged, the latter approach will be more likely to reduce inequality in a meaningful sense; but it will not benefit either the disadvantaged or the advantaged as much as the former approach. Further, in appraising the impact of both population-approach and targeted interventions, it needs to be recognized that interventions may in fact reduce – or increase – inequality in some meaningful sense while simply not doing so sufficiently to cause departures from the standard patterns whereby overall reductions in adverse outcomes tend to be accompanied increasing relative differences in such outcomes and declining relative differences in avoiding the outcome.[8,9] References: 1. Frohlich KL, Potvin. The inequality paradox: The population approach and vulnerable populations. Am J Pub Health. 2008; 98:XXX–XXX. doi:10.2105/ AJPH.2007.114777 2. Pickett KE, Luo Y, Lauderdale DS. Widening social inequalities in risk for sudden infant death syndrome. Am J Public Health. 2005;95:97- 81. 3. Scanlan JP. Can we actually measure health disparities? Chance. 2006:19(2):47-51: http://www.jpscanlan.com/images/Can_We_Actually_Measure_Health_Disparities.pdf (accessed Jan. 21, 2008) 4. Scanlan JP. Race and mortality. Society 2000;37(2):19-35 (reprinted in Current 2000 (Feb)): http://www.jpscanlan.com/images/Race_and_Mortality.pdf (accessed Jan. 21, 2008) 5. Scanlan JP. Divining difference. Chance. 1994;7(4):38-9,48: http://jpscanlan.com/images/Divining_Difference.pdf (accessed Jan. 21, 2008) 6. Scanlan JP. Measurement problems in the National Healthcare Disparities Report, presented at American Public Health Association 135th Annual Meeting & Exposition, Washington, DC, Nov. 3-7, 2007: http://www.jpscanlan.com/images/ORAL_ANNOTATED.pdf (accessed Jan. 21, 2008) 7. Scanlan JP. Recognizing the statistical basis for advances in health care to cause larger relative reductions in mortality in groups with lower base rates. Journal Review. June 9, 2007, responding to Korda RJ, Butler JRG, Clements MS, Kunitz SJ. Differential impacts of health care in Australia: trend analysis of socioeconomic inequalities in avoidable mortality. Int J Epidemiol. 2007;36:157-165: http://www.journalreview.org/view_pubmed_article.php?pmid=17213209&specialty_id=0&sdesc=&emsg= (accessed Jan. 21, 2008) 8. Scanlan JP. The Misinterpretation of health inequalities in the United Kingdom, presented at the British Society for Populations Studies Conference 2006, Southampton, England, Sept. 18-20, 2006: http://www.jpscanlan.com/images/BSPS_2006_Complete_Paper.pdf. (accessed Jan. 21, 2008) 9. Scanlan JP. The misunderstood relationship between declining mortality and increasing racial and socioeconomic disparities in mortality rates, presented at the conference "Making a Difference: Is the Health Gap Widening?" Oslo Norway, May 14, 2001: http://www.jpscanlan.com/images/Oslo_presentation.ppt (accessed Jan. 21, 2008).