The average life expectancy in the US has declined for a third straight year. New research linked that decline to the fact that "working-age" Americans, between ages 25 and 64, have been dying at higher rates. These deaths have been linked to drug overdoses, suicides, and alcohol-related diseases, among other health problems. Multiple experts agree that socioeconomic inequality and a economic hardship may have contributed to this increase in middle-age American deaths. Visit Business Insider's homepage for more stories. The US is the only wealthy country in the world where the life expectancy needle is moving the wrong way.