In the their article identifying widening social inequalities in
sudden infant death syndrome (SIDS) following implementation of the “Back
to Sleep” campaign, Pickett et al. express the view that an inexpensive
public health intervention like that campaign would be expected to reduce
health inequalities since there would be few barriers to universal uptake
of the campaign’s recommendations.1 That view reflects a failure to
appreciate the tendency for beneficial interventions, even very
inexpensive ones, almost invariably to increase demographic disparities in
mortality rates. That tendency stems from the fact that disadvantaged
groups comprise a larger proportion of each segment of the overall
population that is increasingly less able to benefit from an intervention.
Progress is invariably a matter of restricting adverse outcomes to the
point where only those most susceptible to those outcomes continue to
experience them–until, in an ideal world, the adverse outcome disappears
entirely. But every step short of the total elimination of the adverse
outcomes tends to increase the disparity in the rates at which two groups
experience the outcome.
The tendency is readily observable in income data. Blacks are 2.3
times as likely as whites to fall below the poverty line. But they are
2.6 times as likely to fall below 75 percent of the poverty line and 2.7
times as likely to fall below 50 percent of the poverty line. A program
that enabled everyone above 75 percent of the poverty line to escape
poverty would be especially beneficial to blacks, as would a program that
enabled everyone above 50 percent of the poverty line to do so. But each
program would result in an increase in the ratio of the black poverty rate
to the white poverty rate.2
The same holds for programs that reduce mortality or any other
adverse outcome as to which disadvantaged groups are disproportionately
susceptible. The more success a program achieves in reducing the outcome,
the more such outcome will be concentrated among the very most susceptible
groups, and the greater will be demographic disparities in experiencing
the outcome. That does not mean that a program has been unsuccessful, or
even that disadvantaged groups did not disproportionately benefit from it.
For, while such groups may comprise a disproportionate part of the
population continuing to suffer from the outcome, they also comprise a
disproportionate part of the population that the program enables to escape
the outcome.2,3,4
References
1. Pickett et al. Widening social inequalities in risk for sudden
infant death syndrome. Am J Public Health. 2005;95:97-81.
2. Scanlan JP. Can we really measure health disparities? Chance.
2006 (in press).
3. Scanlan JP. Divining difference. Chance. 1994;7:38-39,48.
4. Scanlan JP. Race and mortality. Society. 2000;37:19-35.