Life expectancy at birth in the United States fell by 0.1 year in 2015—to 78.8 years. This seemingly small decline is a big deal and troubling for two reasons. One, a decline in life expectancy does not happen very often. The 2015 decline was the first since 1993, and the 1993 decline was the first since 1980. Two, unlike the 1993 decline in life expectancy—a consequence of HIV's rapid rise to become the 8th leading cause of death—the reason for the 2015 decline is not clear.
That's because there are many reasons. The age-adjusted death rate increased significantly in 2015 for fully 8 of the top 10 causes of death: heart disease, chronic lower respiratory disease, unintentional injuries, stroke, Alzheimer's disease, diabetes, kidney disease, and suicide. The death rate increased for non-Hispanic Whites (males and females) and non-Hispanic Black males. The death rate was unchanged for non-Hispanic Black females and for Hispanics (males and females).
While the National Center for Health Statistics' report does not shed much light on the significance of the life expectancy decline, a New York Times story does, quoting professor of health policy and management at Columbia University, Dr. Peter Muennig, who tells the Times, "a 0.1 decrease is huge."
Source: National Center for Health Statistics, Mortality in the United States, 2015