04/10/2012 04:13 EDT | Updated 06/10/2012 05:12 EDT

Fatal Car Crashes And Income Tax Deadline Linked In Study

TORONTO - This month's income tax deadline day can not only be stressful for those who have left filing their return to the last minute, but it can also be deadly.

A 30-year study of traffic accidents in the United States has found that the country's mid-April tax deadline day is associated with an elevated risk of fatal crashes.

Using data for fatal vehicle crashes for every April 15 over the last three decades, the study found that Americans have a six per cent increased risk of dying on tax day — and a similar risk likely occurs on Canada's tax deadline day, April 30, researchers say.

"We find about the same increase in risk both during the morning hours, the afternoon hours and the evening hours," said lead researcher Dr. Donald Redelmeier, an internal medicine specialist at Sunnybrook Health Sciences Centre in Toronto.

"So it's not all confined to the 11th hour, right before the stroke of midnight. But it prevails for the full day."

That differs from Super Bowl Sunday — another event Redelmeier has studied.

His 2003 analysis of traffic deaths on the day of the hugely popular televised National Football League showdown found a 41 per cent increased risk in the average number of road fatalities over a 27-year period.

But Super Bowl Sunday traffic deaths occurred primarily within three hours following the game's completion — not throughout 24 hours, as is the case for tax-filing day.

Redelmeier, who is often called on to treat victims of vehicle crashes at Sunnybrook's regional trauma centre, said the increased risk on U.S. tax day translates into about 13 deaths per year.

"None of these people had to die ... Road trauma destroys the lives of thousands of people in the United States each year," as it does in Canada, he said.

"And driver error contributes to about 93 per cent of such events."

The study, published in this week's issue of the Journal of the American Medical Association, used tax day road fatalities as a marker for what high stress can do to driver behaviour on any day of the year, anywhere in the world.

"Stress is often speculated as a contributing factor in driver error, and yet stress is almost impossible to study in a scientific manner," Redelmeier said. "Here, we were trying to pull out one particular form of stress."

He said the largest jumps in risk for fatal crashes on tax deadline day occurred during the last two decades, despite the advent of electronic tax filing during that period.

"So that we don't think that what's going on here is increased amounts of driving ... like the proverbial rushing to the post office at the stroke before midnight. We don't think that that's the largest factor here."

Ironically, he said, electronic filing may encourage more people to leave tax-return preparation to the last minute.

The study, which also looked at traffic death data for seven days before and seven days after tax day over 30 years, also found that bad weather, such as snow or rain storms, does not appear to be a factor.

"We looked at different regions, and the increase in risk was about same, in northern versus southern states, west versus east, urban versus rural," Redelmeier said.

Researchers aren't clear on what factors are behind the bump-up in the chance of dying in a road accident on the final day for filing taxes.

While one explanation is that stressful deadlines can lead to driver distraction and human error, sleep deprivation and drinking alcohol could also play a role.

And although the study data only allowed researchers to nail down the six per cent increased risk for fatalities, Redelmeier believes a similar level of risk applies to the spectrum of outcomes that can arise from collisions on roadways — from brain and spinal cord injuries to other kinds of physical trauma and property damage.

Intriguingly, only about 20 per cent of Americans leave their tax filing to the deadline, yet there is still a significantly elevated risk of dying on that day.

"What that means is even if you as an individual have filed early, it doesn't mean you're immunized against the situation, because you live in a community of all sorts of other drivers out there," he said, noting that non-drivers aren't immune either.

"The increase in risk on tax day included the passengers and pedestrians, which is a common theme of all of road trauma — bad driving imposes risks on other people."

The study was not able to look at traffic deaths in Canada on April 30 because of a lack of good data, but he said high stress leads to distracted drivers in this country as well.

"And that stressful tax deadline, like we've got in Canada on April 30, might also contribute to short-term human error and result in fatal road trauma."

Redelmeier said no matter how much stress is being experienced, it's critical that drivers remember to wear their seatbelts, obey the speed limit, restrict alcohol consumption and minimize distractions while behind the wheel.

"Almost every one of these fatal crashes could have been entirely avoided by a small change in driver behaviour. Basic safety practices should not be forgotten at times of stress."