A new study suggests higher mortality rates among Americans younger than 50 are responsible for much of why life expectancy is lower in the United States than most of the world's most developed nations. Most of the excess mortality of those younger than 50 was caused by noncommunicable diseases, including perinatal conditions, such as pregnancy complications and birth trauma, and homicide and unintentional injuries including drug overdose.

Source: U.S. lifespans lags other high-income countries, tied to mortality rates under age 50