The clock time for dawn was 12:00 AM to 5:59 AM; morning, 6:00 AM to 11:59 AM; afternoon, 12:00 PM to 5:59 PM; and night, 6:00 PM to 11:59 PM. Odds ratios are reliable estimates of relative risk when event rates are low from an individual driver's perspective.
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Redelmeier DA, Yarnell CJ. Road Crash Fatalities on US Income Tax Days. JAMA. 2012;307(14):1486–1488. doi:10.1001/jama.2012.450
Author Affiliations: Department of Medicine, University of Toronto, Toronto, Ontario, Canada (Dr Redelmeier; firstname.lastname@example.org); and Evaluative Clinical Sciences Program, Sunnybrook Research Institute, Toronto, Ontario, Canada (Mr Yarnell).
To the Editor: US income tax day occurs yearly around April 15 and is a stressful deadline for millions of US adults. Tax payments influence the long-term health of the economy, but no study has tested how tax deadlines might affect the immediate health of individuals. We investigated the number of individuals involved in a fatal road crash on tax day under the prespecified hypothesis that stressful deadlines might increase the risk of road trauma by impairing drivers or by compromising surrounding individuals from making compensatory adjustments.1
We retrieved tax deadline data from the Internal Revenue Service and fatal road crash data from the National Highway Traffic Safety Administration for the past 3 decades (1980-2009). We used the Fatality Analysis Reporting System, a validated database that included all crashes involving a motor vehicle on public roadways in which at least 1 person died within 30 days (including passengers, pedestrians, or other involved individuals).2 For each tax day, we identified controls as the day 1 week before and 1 week after to evaluate the number of individuals involved in a fatal road crash. This design controlled for year, month, and weekday as well as minimized bias from differences in vehicle technology, gasoline prices, health care access, driver training, and other confounders.
Stratified analyses assessed robustness based on age, sex, region, decade, time of day, position, and initial outcome. We applied statistical methods published previously using binomial tests, 2-tailed analyses, a threshold P value of .05, and StatView version 5.0 (SAS Institute Inc).3 The study protocol was approved by the research ethics board of the Sunnybrook Health Sciences Centre.
A total of 19 541 individuals were involved in a fatal road crash during the 30 tax days (n = 6783; 226 per day) and 60 control days (n = 12 758; 213 per day). The modal person was a young adult man driving in a rural location. Comparisons of tax days with control days yielded an odds ratio of 1.06 (95% CI, 1.03-1.10; P < .001), equivalent to an absolute increase of 404 individuals in fatal road crashes on tax days over the study interval or about 13 individuals during the average tax day.
The relative increase in risk was most apparent during the last 20 years and in adults younger than 65 years (Figure). The increase in risk persisted for different regions, locations, hours, sexes, initial outcomes, and extended to passengers and pedestrians. The 95% confidence intervals were broad yet all subgroups overlapped the main analysis, none showed a significant contrary result, and the majority were statistically significant.
Tax days are associated with an increase in fatal crash risk,4 which is similar in magnitude to the increase in crashes on Super Bowl Sunday.5 One explanation is that stressful deadlines distract drivers and contribute to human error (a national poll suggested that tax day was the second most stressful day in 2011).1,6 Another might be alcohol, yet we found no accentuation during night hours when alcohol consumption may be more frequent. Driving patterns may be altered on tax day. Although electronic submissions might be expected to lessen driving on tax day, we observed an increase rather than a decrease in fatal crashes in recent decades. Additional reasons might include sleep deprivation, inadvertent inattention, and less tolerance of hassles.
Because this study lacked data on alcohol, stress, or driving patterns, future studies should evaluate the reasons for the increased risk as well as potential opportunities for intervention.2,4 In the interim, public health campaigns should reinforce the importance of road safety on tax day, including emphasizing the need to wear seatbelts, avoid alcohol, reduce excessive speed, and minimize distractions.4
Author Contributions: Dr Redelmeier had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Redelmeier, Yarnell.
Acquisition of data: Redelmeier.
Analysis and interpretation of data: Redelmeier, Yarnell.
Drafting of the manuscript: Redelmeier, Yarnell.
Critical revision of the manuscript for important intellectual content: Redelmeier, Yarnell.
Statistical analysis: Redelmeier.
Obtained funding: Redelmeier.
Study supervision: Redelmeier.
Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Funding/Support: This project was supported by the Canada Research Chair in Medical Decision Sciences and the Canadian Institutes of Health Research.
Role of the Sponsors: The funding organizations had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.
Disclaimer: The views expressed are those of the authors and do not necessarily reflect those of the Ontario Ministry of Health.
Additional Contributions: We thank the following for helpful comments: Chaim Bell, MD, PhD, Michael Schull, MD, and John Staples, MD (all 3 with the University of Toronto, Toronto, Ontario, Canada), and Robert Tibshirani, PhD (Stanford University, Palo Alto, California). No compensation was provided to these individuals.
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