Americans died at a higher rate in 2015 than in recent years, according to preliminary research gathered by the National Center for Health Statistics.
The increase is a surprise to experts, who typically see a decline in deaths each year.
The age-adjusted death rate for 2015 was 729.5 deaths per 100,000 people, compared with 723.2 in 2014. An increase in the overall rate is incredibly rare; the last significant uptick in the death rate was in 2005 during an especially bad flu season, CNN reported in June.
It's too early to tell what caused the uptick, but CNN reports deaths from preventable causes, such as firearm deaths and homicides, are up. There were also more suicides, drug overdoses, falls, and accidents in 2015.