Scientists can’t explain it.
The phenomenon of some women losing ground appears to have begun in the late 1980s, though studies have begun to spotlight it only in the last few years.
Trying to figure out why is “the hot topic right now, trying to understand what’s going on,” said Jennifer Karas Montez, a Harvard School of Public Health sociologist who has been focused on the life expectancy decline but had no role in the new study.
Researchers also don’t know exactly how many women are affected. Montez says a good estimate is roughly 12 percent.
The study, released Monday by the journal Health Affairs, found declining life expectancy for women in about 43 percent of the nation’s counties.