Daylight Savings Time may kill

Saturday, Oct 31, 2009

In the October 30, 2008 edition of The New England Journal of Medicine, a Swedish team studied the incidence rates of Myocardial Infarction, i.e. heart attacks, from the 1980s to 2006. The research was supported by the Swedish Heart and Lung Foundation, the Swedish Council of Working Life and Social Research, the Ansgarius Foundation, and the King Gustaf V and Queen Victoria’s Foundation. They suggest that losing an hour of sleep in the Spring is correlated with increased heart attacks.

More than 1.5 billion men and women are exposed to the transitions involved in daylight saving time: turning clocks forward by an hour in the spring and backward by an hour in the autumn. These transitions can disrupt chronobiologic rhythms and influence the duration and quality of sleep, and the effect lasts for several days after the shifts.

We examined the influence of these transitions on the incidence of acute myocardial infarction...

The incidence of acute myocardial infarction was significantly increased for the first 3 weekdays after the transition to daylight saving time in the spring...

In contrast, after the transition out of daylight saving time in the autumn, only the first weekday was affected significantly...

The effect of the spring transition to daylight saving time on the incidence of acute myocardial infarction was somewhat more pronounced in women than in men, and the autumn effect was more pronounced in men than in women.

The effects of transitions were consistently more pronounced for people under 65 years of age than for those 65 years of age or older. The most plausible explanation for our findings is the adverse effect of sleep deprivation on cardiovascular health. According to experimental studies, this adverse effect includes the predominance of sympathetic activity and an increase in proinflammatory cytokine levels. Our data suggest that vulnerable people might benefit from avoiding sudden changes in their biologic rhythms. It has been postulated that people in Western societies are chronically sleep deprived, since the average sleep duration decreased from 9.0 to 7.5 hours during the 20th century...

The finding that the possibility of additional sleep seems to be protective on the first workday after the autumn shift is intriguing... Sleep-diary studies suggest that bedtimes and wake-up times are usually later on weekend days than on weekdays; the earlier wake-up times on the first workday of the week and the consequent minor sleep deprivation can be hypothesized to have an adverse cardiovascular effect in some people... Studies are warranted to examine the possibility that a more stable weekly pattern of waking up in the morning and going to sleep at night or a somewhat later wake-up time on Monday might prevent some acute myocardial infarctions.

Shifts to and from Daylight Saving Time and Incidence of Myocardial Infarction, Dr. Janszky PhD, Karolinska Institute of Sweden, and Dr. Ljung PhD, National Board of Health and Welfare of Sweden, October 30, 2008, http://content.nejm.org/cgi/reprint/359/18/1966.pdf.

And for what?

The history of Daylight Saving Time (DST) has been long and controversial. Throughout its implementation during World Wars I and II, the oil embargo of the 1970s, consistent practice today, and recent extensions, the primary rationale for DST has always been to promote energy conservation. Nevertheless, there is surprisingly little evidence that DST actually saves energy. This paper takes advantage of a natural experiment in the state of Indiana to provide the first empirical estimates of DST effects on electricity consumption in the United States since the mid-1970s...

Our main finding is that—contrary to the policy's intent—DST increases residential electricity demand. Estimates of the overall increase are approximately 1 percent, but we find that the effect is not constant throughout the DST period. DST causes the greatest increase in electricity consumption in the fall, when estimates range between 2 and 4 percent. These findings are consistent with simulation results that point to a tradeoff between reducing demand for lighting and increasing demand for heating and cooling. We estimate a cost of increased electricity bills to Indiana households of $9 million per year. We also estimate social costs of increased pollution emissions that range from $1.7 to $5.5 million per year. Finally, we argue that the effect is likely to be even stronger in other regions of the United States.

Does Daylight Saving Time Save Energy? Evidence from a Natural Experiment in Indiana, Matthew J. Kotchen and Laura E. Grant, Department of Economics at the University of California, Santa Barbara, October 20, 2008, http://www2.bren.ucsb.edu/~kotchen/links/DSTpaper.pdf (National Bureau of Economic Research: http://www.nber.org/papers/w14429).