Jonathan Auerbach and I wrote up some of the age-adjustment stuff we discussed on this blog a couple months ago. Here’s our article, a shorter version of which will appear as a letter in PPNAS.
Wow!! Remember that increasing death rate among middle-aged non-Hispanic whites? It’s all about women in the south (and, to a lesser extent, women in the midwest). Amazing what can be learned just by slicing data.
I don’t have any explanations for this. As I told a reporter the other day, I believe in the division of labor: I try to figure out what’s happening, and I’ll let other people explain why.
I’m sure you can come up with lots of stories on your own, though. When performing your reverse causal inference, remember that people move, and, as we’ve discussed before, the cohorts are changing. 45-54-year-olds in 1999 aren’t the same people as 45-54-year-olds in 2013. We adjust for changing age distributions (ya gotta do that) but we’re still talking about different cohorts.
Here’s how our paper begins:
In a recent article in PNAS, Case and Deaton show a figure illustrating “a marked increase in the all-cause mortality of middle-aged white non-Hispanic men and women in the United States between 1999 and 2013.” The authors state that their numbers “are not age-adjusted within the 10-y 45-54 age group.” They calculated the mortality rate each year by dividing the total number of deaths for the age group by the population of the age group.
We suspected an aggregation bias and examined whether much of the increase in aggregate mortality rates for this age group could be due to the changing composition of the 45–54 year old age group over the 1990 to 2013 time period. If this were the case, the change in the group mortality rate over time may not reflect a change in age-specific mortality rates. Adjusting for age confirmed this suspicion. Contrary to Case and Deaton’s figure, we find there is no longer a steady increase in mortality rates for this age group. Instead there is an increasing trend from 1999–2005 and a constant trend thereafter. Moreover, stratifying age-adjusted mortality rates by sex shows a marked increase only for women and not men, contrary to the article’s headline.
And here’s the age-adjustment story in pictures:
For some reason, the NYT ran a story on this the other day and didn’t age adjust, which was a mistake. Nor did they break down the data by region of the country. Too bad. Lots more people read the NYT than read this blog or even PPNAS.