Finnish researchers have found that the transition to daylight savings time reduces both our sleep duration and efficiency. They monitored the rest-activity cycles of ten adults for ten days a year over two years. After the transition they noted that sleep time was shortened by 60 minutes and sleep efficiency was reduced by 10 percent on average.
But on a positive note, depression rates are set to fall. Researchers from Quebec, Canada say sleeping late increases REM sleep, and excessive REM sleep is linked to depression. They reviewed two studies on depression and sunrise time in cities, and found it was “significantly correlated” with depression rates — later sunrise (corresponding to earlier rising times) was associated with less depression.
A study in the Journal of Periodontology suggests that a chance to enjoy extra daylight can extend the life and health of our teeth and bones. That’s because our bodies get vitamin D through sun exposure. Vitamin D, along with calcium, is essential for preventing bone and teeth disorders.
While polls indicate most people favor extending daylight savings time, there are opponents. The airline industry has said it will cost millions of dollars to change schedules, and numerous time-sensitive computer systems may be affected. Many businesses have been thrown into panic, but candy manufacturers have a reason to smile. This year, Halloween occurs during daylight savings time, giving trick-or-treaters an extra hour of daylight to make their rounds.
To stay in sync with the U.S., Canada and many Caribbean countries will extend their daylight savings time calendars. Daylight savings time is not observed in Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands, and Arizona.
Hildebolt C. F. Effect of Vitamin D and Calcium on Periodontitis. The Journal of Periodontology, Vol. 76, September 2005, pp. 1576-87.
Olders H. Average sunrise time predicts depression prevalence. The Journal of Psychosomatic Research, Vol. 55, August 2003, pp. 99-105.
Lahti T. A. et al. Transition to daylight saving time reduces sleep duration plus sleep efficiency of the deprived sleep. Neuroscience Letters, Vol. 406, October 2006, pp. 174-77.