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Sleep Deficit, Fatal Accidents, and the Spring Shift to Daylight Savings Time

Coren, S. (Department of Psychology, University of British Columbia, Canada)

Contact Person: Stanley Coren (scoren@cortex.psych.ubc.ca)


Some researchers claim that society is chronically sleep deprived, and even small additional reductions in sleep time may have consequences for safety. Supportive evidence was provided by a study of the effects of daylight savings time (DST) on traffic accidents, finding increased accident rates on the Monday following the spring time shift (one hour sleep lost) and decreased rates in the fall (one hour sleep gained). This study attempted to replicate these findings using data on 366,910 U.S. traffic deaths (1986-1995). Comparing the Monday immediately following the DST shift, with the previous and following Mondays, shows the expected spring increase in fatal accidents [RR=1.17, 95% CI=1.07/1.29, 2(1)=10.83, p < 0.001] while the fall time shift produced an insignificant reduction in traffic deaths. Alternative explanations, not involving sleep are that after the spring shift people must drive to work in dimmer light or that those who forget the time shift find themselves late for work and driving with reckless haste. Both predict the accident increase early in the day, while sleep deficit predicts effects later in the day. Patitioning the day into early and late finds only a significant increase in traffic fatalities in the later half of the day [RR=1.13, 95% CI=1.01-1.28, 2(1)=3.89, p < 0.05]. Thus these data are consistent with the hypothesis that a small decrease in sleep duration, such as that which occurs with the spring shift to DST, can significantly increase accident susceptibility.

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Poster Number PAcoren0164
Keywords: Sleep, Accidents, Sleep Deficit, Daylight Savings, Traffic Safety

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Coren, S.; (1998). Sleep Deficit, Fatal Accidents, and the Spring Shift to Daylight Savings Time. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Available at URL http://www.mcmaster.ca/inabis98/occupational/coren0164/index.html
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