(Reuters) - Guns caused the life expectancy of black Americans to drop by more than four years from 2000 to 2016, twice as much as the decline in life expectancy of white Americans during the same period, according to an academic study published on Tuesday.

Assault with firearms accounted for more than three years of the drop among black Americans, while the rest reflected suicides by gun, according to the report in BMJ Evidence-Based Medicine.

The life expectancy for white Americans dropped about two years and nearly three months due to firearms, with assault contributing less than a year.

The study used data gathered from the Centers For Disease Control and Prevention to examine race-specific life expectancy loss in the United States related to firearms.

Bindu Kalesan, an author of the study and a professor at the Boston University School of Medicine, said in a statement that understanding how gun violence affects people of races may help with the development of more effective prevention programs.

Suicides by gun occurred mainly among older white Americans, researchers found, limiting its negative impact to one year and more than seven months. For black Americans, life expectancy decreased by about seven months because of suicides by gun.

A sharp drop in life expectancy occurred around age 20 among both black Americans and white Americans, the study showed. For black people under the age of 20, assaults with firearms were to blame. For white Americans above the age of 20, the drop was driven by suicides by gun.