The disappearing income gradient in New York City birth outcomes: thirteen years of convergence from 1988 to 2001.
OBJECTIVE
Income has long been identified as a potent determinant of infant mortality, yet little is known about the stability of its influence over time in defined populations. The objective of this study was to characterize trends in the income gradient in infant mortality in New York City from 1988 to 2001.


METHODS
An ecological analysis was conducted of infant, neonatal, and postneonatal mortality rates in 30 health districts from 14 years (1988-2001) of birth cohorts of the 5 boroughs of New York City divided by quartile of income based on the 1990 census (N = 1,692721 births). Infant mortality (deaths occurring at <365 days of age), neonatal mortality (deaths occurring at <28 days of age), and postneonatal mortality (deaths occurring from 28 to 364 days of age) expressed as rates per 1000 live births were measured.


RESULTS
From 1988 to 2001, infant mortality in the highest income quartile in New York City fell 50.5% from 10.5 to 5.2, whereas in the lowest income quartile, it fell 62.6% from 17.4 to 6.5 per 1000 live births. The equivalent declines in neonatal mortality were 46.6% from 7.3 to 3.9 in the highest income quartile and 61.4% from 11.4 to 4.4 per 1000 live births in the lowest income quartile. For postneonatal mortality, rates fell 58.1% from 3.1 to 1.3 in the highest income quartile and 65% from 6 to 2.1 per 1000 live births in the lowest income quartile. Adjusted for covariates, relative to the highest income quartile, infant, neonatal, and postneonatal morality rates in the lowest income quartile declined 0.36 (95% confidence interval [CI]: -0.52 to -0.19), 0.20 (95% CI: -0.34 to -0.07), and 0.15 (95% CI: -0.23 to -0.07) per 1000 live births more per year.


CONCLUSIONS
From 1988 to 2001, New York City witnessed a significant convergence in the income gradients of infant, neonatal, and postneonatal mortality rates. Understanding the origins of this trend should constitute an important public policy priority.
Racine
Andrew D
AD
Department of Pediatrics, Albert Einstein College of Medicine/Children's Hospital at Montefiore and National Bureau of Economic Research, Bronx, New York 10461, USA. aracine@montefiore.org
Joyce
Theodore J
TJ
D001724:Birth Weight; D005260:Female; D006801:Humans; D007182:Income / Q000639:trends*; D007223:Infant; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D009519:New York City / Q000453:epidemiology; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D017062:Small-Area Analysis