I have long had a fascination with life expectancy. One of the things that bothers me so is that life expectancy in the United States is so much lower than in other developed nations. Is that the fault of the health care system? Is it something else?

In a recent study in JAMA, three researchers set out to answer this question. "Major Causes of Injury Death and the Life Expectancy Gap Between the United States and Other High-Income Countries":

The United States experiences lower life expectancy at birth than many other high-income countries. Although research has focused on mortality of the population older than 50 years, much of this life expectancy gap reflects mortality at younger ages, when mortality is dominated by injury deaths, and many decades of expected life are lost. This study estimated the contribution of 3 causes of injury death to the gap in life expectancy at birth between the United States and 12 comparable countries in 2012. We focused on motor vehicle traffic (MVT) crashes, firearm-related injuries, and drug poisonings, the 3 largest causes of US injury death responsible for more than 100?000 deaths per year.

One of the tricky parts of life expectancy comparisons is that causes of death at younger ages have so much more of an effect than causes of death in the elderly. After all, when a 25 year old dies, that has more of an effect on the calculation than when a 75 year old dies.

This study used data from the US National Vital Statistics System and the WHO Mortality database to calculate the death rates the US and 12 high-income countries (Austria, Denmark, Finland, Germany, Italy, Japan, the Netherlands, Norway, Portugal, Spain, Sweden, and the United Kingdom). Then they used those data to calculate the life expectancy of people in the US and other countries with and without car accidents, gun-related injuries, and drug poisonings.

In 2012, the all-cause, age-adjusted death rate per 100,000 people was 865 in the US and 772 in the other countries. This translated into life expectancies of 78.6 (other countries) and 76.4 (US) in men and 83.4 (other countries) and 8.2 (US) in women. In other words, the gap was about 2.2 years.

The three injury-causes of death accounted for almost half of the difference in men (1.02 years), and almost 20% of the difference in women (0.42 years). Gun deaths alone accounted for 21% of the gap in men and 4% in women. Car accidents accounted for 13% of the gap in men and 6% in women. Drug poisonings made up 14% of the gap in men and 9% of the gap in women.

This is a chart I made which shows the age-adjusted death rates for men in all the studied countries. The columns (left y-axis) are those caused by the three injuries (car accidents, guns, and drug poisonings). The line (right y-axis) are all other causes. As you can see, the US is the clear standout with respect to the injuries. With respect to all other injuries, though, the US is more... average.








The problem is that life expectancy weights mortality at younger ages more heavily than the age-adjusted death rate. Therefore, even though Portugal, for instance, has a higher all-cause age-adjusted death rate higher than that of the US, its life expectancy is still longer than the US because more people in the US die at younger ages.

Drug poisonings are the largest cause of US injury death. Is this because of opioids? Maybe. We need good data to tell. Regardless, it's clear that a significant portion of the life expectancy gap is caused by car accidents, firearms, and drugs. We need to focus on them, from a public health perspective, in addition to improving the health care system if we're going to close this gap.



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