WASHINGTON — Life expectancy declined slightly for white Americans in 2014, according to new federal data, a troubling sign that distress among younger and middle-age whites who are dying at ever-higher rates from drug overdoses is lowering average life spans for the white population as a whole.

The new federal data, drawn from all deaths recorded in the country in 2014, showed that life expectancy for whites dropped to 78.8 years in 2014 from 78.9 in 2013. Men and women had declines, but because of statistical rounding, the decline did not appear as sharp among men.

Life expectancy for women fell to 81.1 in 2014 from 81.2 in 2013. The average life span for men also fell, but not enough to sink below 76.5 years, their life expectancy in 2013.

“The increase in death in this segment of the population was great enough to affect life expectancy at birth for the whole group,” said Elizabeth Arias, the statistician at the National Center for Health Statistics who analyzed the data, referring to whites from their mid-20s to their mid-50s. “That is very unusual.”