Infant Mortality Rate: Numbers Matter


I think it’s important.

Plus, as we get closer and closer to election time, we’re gonna be discussing this more and more.

Plus, the debate is raging over at Poison Your Mind concerning it.

What is it?  What are we debating and how can there be a debate?

Well, it is Infant Mortality rates and how they can be used to measure a nation’s health care system.  Rightly or wrongly.

Okay, so this is a description of 3 nations.

These three nations have the exact same number of people but they have a mix of social factors and health care methods.  Let’s take a look at those 3 nations and try to decide which one has the better medical care delivery system using infant mortality rates.

First, the raw numbers:

Which nation wins?  Which nation’s medical care delivery system is doing the better job if you look at infant mortality rate?

Easy.  Nation B.  Its rate is the lowest.

But check it out.  What if I told you that Nation A and Nation B delivered the EXACT same medical care to infants?  How could that be explained?

Notice the added detail.  For illustration purposes, I have differentiated births by 2 factors; birth weight and gestational time.  Babies are born either “On Time” or “Early”.  Further they can be “Low Birth Weight” or “Normal Birth Weight”.  This creates 4 combinations each with it’s own rate.

Now look at the last column, Category Rate.  This represents a fictional mortality rate for each category.  Nation A and Nation B have the exact same mortality rates for each specific category and then as an aggregate.  If that’s true, then you have to argue that each Nation is delivering care to it’s infants equally well.  So how do we explain the difference in the overall mortality rate?

The second to last column, % of births.

See, Nation B has fewer births that are classified as “At Risk”.  Those are precisely the very births that are hardest to administer care too.  Nation A isn’t doing a worse job at their infant care, they just have proportionately more at risk births to deal with.  In fact, you could argue that given they have a higher drain on their resources AND they are keeping pace, they are doing BETTER than Nation B.

Now, look at what happens when you change the OTHER set of numbers:

Now Nation A is being compared to Nation C.  Again, Nation A has numbers that look worse.  And this time they really are.  Both nations have the same proportion of “At Risk” births but the category rates have changed.  Nation C is 1 percentage point better in each category.  No surprise that Nation C is seen to have the better medical care delivery system.

But what happens when you compare Nation B to Nation C?  That is, BOTH columns of numbers are changed?  Do the “results” reflect reality?

Let’s look:

Nation B wins, right?

Wrong.

In this case, Nation C is handling each category better than Nation B is.  They rank better in each of the 3 “At Risk” categories AND they do better at the births that rate “normal” in both weight and gestation.

The difference?  Nation B is having more births that register in that “Normal – Normal” category.  As a result, they score better in the over all scoring.

But can you argue that Nation B is doing better at providing medical care to it’s infants?

No.

You CAN argue that Nation B is doing something right in that they have fewer “At Risk” births.  But THAT is a different thing altogether than making the case they provide better medical care.

They simply don’t.

UPDATE: Numbers changed to reflect deaths per 100,000

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3 comments
  1. Moe said:

    pino – the usual comparisons don’t address quality of care. They address mortality numbers period. So if there are fewer at risk births as a result of better prenatal care, that’s a live birth. If there are more premature births – often as a result of poor prenatal care – and those babies survive, it’s counted the same – a live birth. And if the premie dies, it’s counted at a mortality.

    Lots of factors come into it as you say, but the charts commonly out there just measure survivors vs non survivors without commenting on the quality of the care.

    • Moe said:

      Or that’s my impression anyway.

    • pino said:

      usual comparisons don’t address quality of care. They address mortality numbers period.

      I suspect you’re right; there is no indication that the governing body is doing anything to attempt to measure apples to apples.

      And if the premie dies, it’s counted at a mortality.

      Which brings up an interesting point. In some nations, if a baby doesn’t survive the first 24 hours, it’s not counted as a live birth. In other nations, the baby has to meet minimum weight restrictions. Others a minimum length restriction. Other still…they have to meet both.

      The larger point is that America has a larger % of the population that delivers at risk pregnancies and births. Given that fact, we fit into Nation A above, and I suspect we actually fit into Nation C. We ARE better at providing care to at risk children, we just have so many that it doesn’t reflect in the traditional WHO and CIA numbers.

      Fascinating stuff.

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