Why Does the US have High Infant Mortality?

A brief summary of this paper  by economists Alice Chen, Emily Oster, and Heidi Williams.

The US has about double the rate of infant mortality (defined as deaths in the first year of life) as other developed countries, such as Finland or Austria.  These are still fairly low rates — 6 in 1000 in the US  vs 3 in 1000 in Finland — but that still amounts to a difference of 15,000 extra US deaths a year, which is a tragedy.

So, what are we doing wrong?

First, we should ask how much of this problem is due to reporting differences. Is it just a statistical artifact?  The authors conclude that it’s not.  When you compare comparably-reported samples, the US infant mortality disadvantage shrinks but doesn’t disappear.

To drill down in what’s really causing the problem, we should distinguish between neonatal deaths (in the first week after birth) and non-neonatal deaths (among babies older than a week.)

The US has a small disadvantage in neonatal deaths, which is entirely explained by lower birth weight infants in the US compared to Europe.  Once you control for birth weight, the US is actually at an advantage relative to European countries.

Most of the US disadvantage, however, is for older infants.  67% of the geographic variation in infant mortality comes from non-neonatal deaths. And most of that is concentrated in lower socioeconomic classes.  Among the lowest education group, the US has an excess infant mortality of 1.3 deaths per 1000 compared to Finland, and 1.8 compared to Austria; among children of college-educated parents, the US’s excess mortality is only 0.04 deaths per 1000 compared to Finland, and 0.27 compared to Austria.
Within the US, geographic patterns of infant mortality follow the same trend. Neonatal mortality is pretty constant from region to region and doesn’t depend much on socioeconomic class; postneonatal mortality varies with income.

So what’s killing poor American babies?

SIDS, or Sudden Infant Death Syndrome. It kills 0.699 US babies per 1000, compared to 0.226 in Finland and 0.185 in Austria.  SIDS is a catch-all term referring to infant deaths without known cause; we currently do not know the physiological cause of SIDS.

The top categories of infant mortality are

  • congenital abnormalities and low birthweight complications
  • SIDS
  • respiratory problems
  • accident
  • assault
  • “other”

In every category but the first (which mostly concerns neonatal mortality), the US has at least twice the death risk of Finland and Austria.

In other words, the largest share of the US’s excessive infant mortality has to do with something around a more unsafe home environment for babies born to poorer parents.  

(While we don’t know what SIDS is, and I’ll investigate it in more detail later, we know it correlates with having things in the baby’s sleeping environment that could suffocate it.)

The excess infant mortality for the US over other European countries shrinks with household income, and disappears altogether for households earning more than $60,000 a year.

What’s the practical takeaway?

  1. If you’re an affluent American parent who wants to reduce risk to your baby, moving to Europe isn’t likely to help. You’re already outside the category that has elevated risk.
  2. The biggest absolute risk to a baby’s life occurs during the first week of life (this is why we want to prevent birth defects, preterm births, low birth weight, and birth complications, all of which will be covered in detail later), and this does not vary that much with socioeconomic status or geography. If you’re an affluent parent you do want to pay attention to reducing your risk here.
  3. In developed countries, most of what kills babies after the first week of life is probably something like “parenting mistakes” — accidents, assaults, and whatever SIDS is.  This is also something to pay attention to, but probably less of a priority for this blog’s readers, given that it varies quite dramatically with socioeconomic status.
  4. If you were making policy (which is the perspective this paper was written from), the priorities are reversed. To reduce the US’s infant mortality rate, health policy should focus less on what happens during pregnancy and around birth, and more on what happens after the baby comes home from the hospital (making sure disadvantaged parents have better resources for taking care of new babies.)

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