Although the death rate in the U.S. has fallen, economists at the Princeton University have identified a particular group for which the death rate has been steadily increasing -- the working class middle-aged white Americans.

According to researchers Angus Deaton and Anne Case, rise in the use of drugs and alcohol, and suicide is to be blamed for an increase in the death rate among middle-aged non-Hispanic Americans. The death rate among people aged between 45 and 54 has risen by 22 percent due to a steady and continuous increase in alcohol and drug use since 1999.

The researchers believe that the increase in death rate during the late 1990s is probably related to an increase in availability of certain prescription painkillers.

In the past, federal researchers have shown their concern over the increasing number of deaths from drug overdose and suicides. Also, government findings suggest that a bulk of those deaths occurs among middle-aged and white men.

Building on the government findings, the Princeton researchers decided to break down the number of deaths by race and age. The researchers found that middle-aged white Americans were doing the worst in terms of number of deaths in America across all categories of groups.

Although it is not clear why this particular groups shows higher death rate than other group, studies suggest that white Americans have been at a greater risk of attempting suicides when they face mental or physical hardship. In addition to prescribed opioid painkillers, education has also been an important factor. Death rate was found to be high among whites with education no more than a high school diploma.

The complete details of the study were published by the Proceedings of the National Academy of Sciences.