Monday, January 11, 2016

Mortality and Age

I spent some time recently picking through CDC’s mortality data. My curiosity was piqued by recent reports of exploding mortality rates due drug poisonings. Luckily you can download the data from CDC’s Wonder database and cut it any way you like. Here’s what I found. Rates are given as deaths per 100k population. The CDC doesn’t have accurate population figures above age 85, so I can’t get those mortality figures from the CDC. They are excluded from my table. The CDC’s data query automatically calculates the mortality rate for you. I’ve added three columns: the change in mortality at each age ( (final – initial )/ initial), and the effect of one year of aging in both 2000 and 2014 (calculated as “this age’s mortality – prior age’s mortality”). So what does it tell us?
(Table at bottom of post.)

Despite recent alarmism, I see mostly good news. The vast majority of age groups (which you can get by each single year!) see a decline in mortality over the past decade and a half. For eleven age groups, people age 25 – 35, mortality has actually increased. That’s not to say things look worse if you’re a 30-year-old. Your life expectancy at age 30 isn’t just based on your morality at age 30; it’s also based on mortality at all years *after* 30. A randomly picked 30-year-old in 2000 could expect another 48.3 years of life (see here, page 25); a 30-year-old in 2013 could expect another 50.1 years of life ( see here, page 12). So this age category is not worse off than it was just over a decade ago. The mortality at any given age is a small piece of the pie, since someone is pretty unlikely to die in the 11 years that span 25 to 35. The improvement in mortality at older ages makes up for the loss in that decade.

What really struck me was how mortality changes as you age. When people talk about drug policy or gun policy, they’re talking about a few points per 100k. If you believe the CDC’s figures, there are about 15 drug poisonings per 100k. Gun homicides are significantly smaller.  These magnitudes, while disturbingly high, pale in comparison to the effect of aging even a few years. Aging from 30 to 35 increases your mortality by 31.9 points (deaths per 100k per year). Aging from 40 to 41 increases your mortality by 21.1 points.  It accelerates quickly from there. Aging from 50 to 51 increases your mortality by 48.1 points (possibly that’s a mild outlier). Aging from 60 to 61 drives up mortality by 75.5 points.

Look at the improvements for ages 0 – 20. These are massive improvements in our earliest years. The improved mortality at age 0, an age at which mortality is famously quite high, is especially good news. People in their mid-60s to mid-80s (where the CDC data stops) are also seeing some impressive gains. All-cause mortality is dropping 20% or more for these ages. A recent paper by Angus Deaton, 2015’s winner of the Economics Nobel, shows how a few age and race demographics are seeing some losses (or at least failing to realize the gains seen in other demographics). But the overall story is a hopeful one. Relevant to my point, a critique  I found of the Deaton paper points out that the 44 – 54 age cohort has gotten older. The mortality effect of sheer aging could explain some (not all) of the backsliding in this demographic (specifically the non-Hispanic white 44-54 demographic).

If we fixate on middle years, age 30 – 60, the average person was 43.6 in 2000 and 45.1 in 2014. Aging that year-and-a-half adds 34 points to your mortality (using 2014 mortality figures; obviously I have to extrapolate a little for fractional years). For comparison, the largest single cause of death in this age group in 2014 is ICD code C34.9, “Bronchus or lung, unspecified – malignant neoplasms” (lung cancer, I presume), which comes in at just under 20 deaths per 100k. A year and a half of aging has a larger magnitude than any single cause of death. I don’t want to overstate my point; admittedly the codes are pretty narrow, and the mortality for “all cancer” or “all heart conditions” would probably be larger. And you may be saying, “No crap. Older people die more.” Still, the magnitudes surprised me.

I don’t want to diminish the importance of social problems like gun violence and drug overdoses. The rates are small, but the total numbers of victims are in the tens of thousands, and each one is a tragedy. I’m not advocating that we compare every problem to “one year of aging” and dismiss it if it’s a lot smaller. Any particular policy approach to any particular problem needs its own cost-benefit analysis. If there’s a problem that kills only 10 people a year and it can be solved for, say, $100k, we shouldn’t flippantly ignore the problem because of its smallness. We should spend the money! And if a problem kills 100,000 people a year but doesn’t respond *at all* to a multi-billion dollar “Just Do Something” government policy, we should stop wasting our money. The overall magnitude of the problem is irrelevant to the question of how to address it (or who should address it, or whether or not to address it). If we simply ignored all problems smaller than “the effect of a year of aging on mortality” we’d leave a lot of important, and more to the point solvable, problems unsolved. Individual problems need to be understood and addressed specifically and one-at-a-time, but we should certainly quantify them and put them into perspective.  

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