(Bloomberg News) Death and taxes aren't only certain, they also seem to share a same deadline in the U.S., according to a study that points to the role of stress in fatal accidents.

Deaths from traffic accidents around April 15, traditionally the last day to file individual income taxes in the U.S., rose 6 percent on average on each of the last 30 years of tax filing days compared with a day during the week prior and a week later, according to research published in the Journal of the American Medical Association.

Even allowing Americans to file their taxes electronically hasn't negated the crash trend, lead researcher Donald Redelmeier said. The findings suggest stress, lack of sleep, alcohol use and less tolerance to other drivers on tax deadline day may contribute to an increase in deaths on the road, Redelmeier said.

"An increase of risk in this magnitude is about the same as what we observe on Super Bowl Sunday, a time notorious in the U.S. for drinking and driving," said Redelmeier, a professor of medicine at the University of Toronto in Canada, in an April 6 telephone interview.

The research showed that there were 226 fatal crashes for each of the 30 tax days and 213 fatal accidents for each of the 60 control days.

Stressful Deadlines

"Our research suggests that stressful deadlines can contribute to driver error that can contribute to fatal crashes," Redelmeier said. "People have, for a long time, speculated that psychological stress may contribute to real world crashes, but this is the first study to pin that down."

The study, which appears as a research letter in the medical journal, looked at tax deadline data from the Internal Revenue Service and fatal traffic accident data from the National Highway Traffic Safety Administration from 1980 to 2009. The researchers then used a database to identify crashes that led to deaths. For every tax day, they also identified a day one week before and one week after as a comparison.

Redelmeier said drivers who are stressed should remember to buckle their seat belts, obey the speed limit, avoid alcohol, minimize distractions and refrain from driving recklessly.

"Under normal circumstances, everyone nods their heads agreeable," he said. "Under stressful circumstances, it's when you tend to forget these pieces of advice."