Just when some of us start getting really old, they begin lowering the life expectancy. How does that work? Who in Washington is to blame for this?

For decades the average life expectancy, a general measure of a population’s health and well-being, has been going up and up and up in the United States. And in other developed countries around the world.

Last year the average life expectancy was 78.7 years, which is more than twice what it was for men 100 years ago. (Thank you, Alexander Fleming, for 1928’s penicillin family of antibiotics.)

But this was the second annual decline in a row. You may not think two-tenths of a year is very much. Tell that to someone who might lose 72 days of life.

And it’s the downward trend that’s bothering experts, which is actually mirrored in other developed countries.

With minor blips for things such as world wars, the average U.S. life expectancy has been generally growing for the last century. By 1950 the average for men was 65.6 years, and women 71.1. Women tend to live longer because they have much easier lives. (Relax, just kidding.)

By 1980, it was up to 70 and 77.4. By 1998, 73.8 and 79.5.

After leading the developed world for much of that time, the United States has fallen 1.5 years behind a handful of other developed nations.

So, what’s going on? Ans: A number of things, some passing, some apparently systemic.

Reuters reports it’s a combination of factors starting with a particularly vicious cycle of flu seasons, which is especially deadly among the elderly. Many population cohorts like baby boomers are aging and succumbing to diseases that often claim the elderly like pneumonia, cardiovascular and Alzheimer’s diseases.

In the U.S. a major reason for the life expectancy decline came from younger generations, people in their 20s and 30s who died from the ongoing epidemic of drug addiction and overdoses.

One study’s lead author is Dr. Steven H. Woolf of Virginia Commonwealth University. He said:

A leading cause is fatal drug overdoses — fueled by the opioid epidemic. But we make a mistake if we focus only on the drug problem.

Woolf also cited what he calls “deaths of despair,” fatalities stemming from alcoholism and suicide.

That study also uncovered a growing midlife death rate from numerous diseases of the lungs, heart, lungs, digestive systems and other organs and rising death rates during pregnancy and early childhood.

The specific reasons for the increase in deaths caused by drugs and alcohol, particularly among white Americans, Woolf said, is “unclear, complex, and not explained by opioids alone.”

He added, “Something far-reaching is affecting the health of Americans in the prime of their lives.”