Daylight Savings – History and Myth: Don’t Forget to Change the Batteries In Your Smoke Detectors.

Once again the time has come that we must advance our clocks one hour forward; otherwise we will be at least an hour late too all our appointments.  This is also the time we are reminded to replace the batteries in our smoke detectors.  It goes without saying that practically everyone knows the effects losing an hour of sleep has on our bodies without needing to refer to academic research or journals – we are sleepy and drowsy!  Loss of sleep or disruption in sleep patterns are the immediate and primary effects of Daylight Saving Time (DST). We must also remember the secondary effects of drowsiness such as the possibility disruptive sleep patterns can have on other cognitive activities.  This begs the question; does one hour loss of sleep really have a large impact on our cognitive abilities such as driving?

Brief History of Daylight Savings Time

Many people credit Benjamin Franklin for DST; although the idea was drafted on an essay he composed on a whim.  According to the Encyclopedia Britannica, the United States, along with other countries, adopted DST during World War I to conserve on fuel reducing the need to power artificial light (Betts, 1998).  During World War II, around spring of 1942 to fall of 1945, DST was adopted year round in what was known as “double summer time” (Betts, 1998).  Today, DST begins the second Sunday of March and ends the first Sunday in November.

Collision Rate

In a 1998 article posted in The New England Journal of Medicine, a study was done to determine if changing the clocks either ahead an hour or back an hour made any significant changes in collision rates.  The study was done by comparing the Monday after the beginning of DST, one week prior to the beginning of DST and the one week after clocks advanced an hour.  The same study was done comparing the collision rates one week prior to the end of DST, the Monday after clocks went back an hour, and the Monday one week after DST ended.  In one study done by Dr. Stanley Coren, he noticed an increase of 8% more collisions after clocks moved ahead and a 7% decrease in collisions in the fall after clocks moved back (Coren, 1998).  In that study Coren concluded that the increase in collisions in the spring was due to the loss of one hour of sleep and the drop in the fall was due to having the extra hour of sleep.  In this same article, Dr. Alex Vincent tested Dr. Coren’s hypothesis and in his study found no significant difference in collision rates the Monday right after the time change and the Monday’s one week prior or after the time changes in either spring or fall (Coren, 1998).

Tale (Tail) of Two Studies

To understand why there is a difference one needs to understand how the studies were calculated.  Coren used a Relative Risk (RR) method where Vincent used a t-test.  The RR method compares incidence based on risk factors (i.e. those exposed the day after the one hour of less or more sleep versus those who have not been exposed he day after).  The t-test is a more complicated test where it measures the significance of a collision occurring based on the confidence levels (i.e. comparing figures with normal distribution factoring variations and standard deviations).  Where Coren’s study basically compared those the day after DST began and ended to those a week prior and a week after, Vincent’s study took into consideration that all other factors were not equal by using the t-test.  Hence, Vincent concluded, “The results of both a graphical analysis and the variability estimation of 10 years of data failed…to support Coren’s hypothesis. The effects reported by Coren may stem from the increased number of vehicles on the road and the increased number of kilometers traveled in the extra daylight hour in the spring, rather than from the minor disruption in circadian rhythm induced by the loss of one hour of sleep” (Coren, 1998).

Does Darkness Kill?

In 2014, Time magazine posed an article stating, “Darkness kills and sunlight saves lives” (Worland, 2014).  Although this article does not provide studies that the change in time is directly responsible for accidents or collisions, it does provide a warning for people and pedestrians to be careful of the earlier time of sunset and darkness.  The article explains that people have a tendency to maintain their habits immediately following the time change (Worland, 2014). People driving, especially familiar routes tend to overlook other cars or drivers within their proximity in darkness resulting in increased risk of accidents.

In Conclusion

With many different studies done comparing the effects of DST, there is no direct evidence that changing clocks increase the risk in collisions.  It is best to maintain healthy sleeping habits, get plenty of rest, drink plenty of water and do whatever you can to stay in shape such as exercise.  Collisions can happen year round in any time zone.  But most importantly, remember to change the batteries in your smoke detectors!

Works Cited

Bettis, J. (1998) Encyclopedia Britannica. Daylight Saving Time. Retrieved from https://www.britannica.com/topic/Daylight-Saving-Time

Coren, S. (1998). Effects of Daylight Savings Time on Collision Rates. New England Journal Of Medicine, 339(16), 1167-1168

Worland, J. (2014). How Daylight Saving Time Can Be Dangerous. Time.Com, 1.