Clockwatching

Impress your mates at the pub with your startling repertoire of esoteric medical knowledge

What happens this year on 26 March in Europe, is delayed until 2 April in America, but doesn't occur in Japan at all? Well, in those countries taking part, it's time to turn the clocks forward one hour, marking the start of daylight saving time (DST), or summer time as it's also known. Now you might groan about losing valuable minutes for partying, studying, or sleeping (your priorities changing as you progress through the course), but are there any tangible benefits to this annual ritual? And what about the health implications of daylight saving that don't often get a mention?

Origins

Benjamin Franklin came up with the bright idea in 1784, to make better use of daylight and so reduce the amount of money wasted on candles in 18th century Paris.^w1 By having the population rise at dawn and go to bed at sunset, as well as rationing candle sales and putting a tax on houses with shutters, he estimated (not entirely seriously) that anywhere between a150m and a400m in today's money could be saved.

The idea didn't resurface until 1907 when a London builder, William Willett, advocated advancing the clocks by 20 minutes on each Sunday in April and reversing the process in September.^w2 It found limited support until the first world war, when Britain, Germany, and other countries adopted daylight saving in 1916 to boost wartime production and save coal. The US followed suit for seven months in 1918, but public opposition led to Congress overriding the measure against the wishes of President Woodrow Wilson—it wasn't until the second world war that Franklin Roosevelt introduced it again across America. At the same time in the UK, political enthusiasm for the energy savings associated with DST led to the introduction of double summer time for the duration of the war, whereby the clocks were advanced two hours ahead of Greenwich Mean Time (GMT) in the summer and stayed an hour ahead of GMT for the rest of the year.

Fast-forward to today, and roughly 70 countries have daylight saving time, although when it starts, how long it lasts and how much of each country is affected varies widely.

Benefits

Accident reduction

A reduction in fatal road traffic accidents is often cited as the major public health benefit of daylight saving time. When Great Britain experimented with maintaining DST all year round between 1968 and 1971, it's thought about 2,500 fewer people were killed or seriously injured during the first two winters of the trial—the equivalent of an 11.7% reduction in casualties for the whole country. Although morning casualties increased, the number was far outweighed by the drop in casualties in the longer evenings.^w3 Smaller studies in the UK have confirmed this trend, with improvements in safety primarily for pedestrians, cyclists, and school children.^{w4 w5} More recently, the Royal Society for the Prevention of Accidents has estimated that 450 deaths and serious injuries occur during the five months of the year when DST is not in operation in the UK.^w6 In the US, the Insurance Institute for Highway Safety estimated that 901 fatal crashes could have been prevented over the years 1987-91 if DST had been retained year round due to the availability of an extra hour of daylight for the busier evening traffic rush.^w7

Unfortunately “unambiguous” and “evidence” rarely go together. The three year British trial of DST coincided with the introduction of random breath testing and new speed limits—powerful incentives for drivers to improve their behaviour regardless of how bright the evening is. Studies have shown an increase in road accidents during the first few days of DST (by as much as 8%)^w8 and unexpectedly following the end of DST^w9 which are attributed diversely to loss of an hour's sleep, alcohol, fatigue, and the fact that the early morning period is intrinsically risky.

Energy savings

Just as importantly for the planet, using daylight more efficiently could mean modest but significant energy savings and reduced pollution. As a result of the Arab oil embargo in the 1970s, the US Congress experimented with extended DST for two years (18 months over that period instead of the normal 12).

When the US Department of Transport evaluated the effectiveness of the trial, it found that roughly 100000 barrels of oil were saved daily in March and April of 1974 and 1975 by having DST.^w10 Extending this finding, energy stricken California estimates that an extension of DST for the winter months could reduce electricity use by 0.5%.^w11 These savings are mainly due to reduced domestic consumption thanks to the extra hour of daylight in the evenings.

However, before we rush to adjust our clocks, a senior official in the US Department of Transport recently sounded a note of caution: “There have been dramatic changes in lifestyle and commerce since we completed our studies that raise serious questions about extrapolating conclusions from our studies into today's world.”^w10

She emphasised that their work is over 25 years old, was limited in scope, and has had its methods questioned (for example, failing to consider that reduced electricity use could be offset by increased petrol consumption owing to extra evening travel)^w12—so we haven't found an alternative to Kyoto just yet.

General wellbeing

Claims have been made that brighter evenings would increase our exposure to daylight and encourage outdoor activity, fitness and health. Supporters of extended DST also maintain that more time spent in the sunlight would reduce vitamin D deficiencies, especially in children and elderly people, and help people with depression^w13 and seasonal affective disorder (SAD)—a specific type of depression believed to be related to reduced exposure to sunlight.^w14 As low vitamin D levels are a problem for 6-18% of the elderly US population,^w15 rocketing to 57% of the general inpatient population,^w16 and with anywhere up to 500000 suffering from SAD in the UK alone,^w17 the public health benefits of DST could be far-reaching but have not been proved.

Exceptions to benefits

Nevertheless, although we might agree that all these ­benefits are worth while, our bodies beg to differ when actually faced with the change. Circadian rhythms, our own biological clocks, regulate behavioural and physiological processes and are synchronised by the daily light-dark cycle. Changing over to DST in the spring is thought to upset this cycle in healthy adults who get less than eight hours sleep (most medics) or are more active in the evenings,^w18 and disruption is also seen for five days after DST ends.^w19 Those few transition days are particularly difficult for anyone with depression20 as well as teenagers and adolescents, whose body clocks are already poorly synchronised to daylight thanks to delayed secretion of melatonin, the body's “sleepiness” hormone.^w21 All in all, the only ones enjoying changeover day itself will probably be those irritating individuals who have never missed a night's sleep and finish a day's work before the rest of us are even out of bed, but, to quote Oscar Wilde, “Only dull people are brilliant at breakfast.”

Conclusion

Despite mixed reports, governments look set to continue tinkering with the issue. George Bush, mindful of his country's addiction to oil, has extended DST in the US by a month, starting in 2007. In the UK, frustrated by a decade of government dithering, the Royal Society for the Prevention of Accidents has called for DST to be in place throughout the winter, with double summer time from March to October (two hours ahead of GMT); a throwback to the war years, this would have the effect of abolishing GMT, putting the UK in the same time zone as western Europe.^w14 While some will be quick to criticise any possibility of change, a chance that hundreds of road traffic accidents could be prevented means that the plans deserve a fair hearing at the very least; whether they will be implemented is a different matter.

I thank Kevin Clinton, road safety adviser, Royal Society for the ­Prevention of Accidents, for his help.

1. Franklin, B., "An Economical Project: Daylight Saving." A letter to the editor of the Journal de Paris April 26, 1784 http://webexhibits.org/daylightsaving/franklin3.html (accessed February 10, 2006)
2. Franklin, B., "An Economical Project: Daylight Saving." A letter to the editor of the Journal de Paris April 26, 1784 http://webexhibits.org/daylightsaving/franklin3.html (accessed February 10, 2006)
3. Home Office, "Review of British Standard Time," Cmnd 4512: HMSO, 1970
4. Whittaker, J.D., "An investigation into the effects of British Summer Time on road traffic accident casualties in Cheshire," J Accid Emerg Med 13 (1996): 189-92
5. Adams, J., White, M., Heywood, P., "Year-round daylight saving and serious or fatal road traffic injuries in children in the north-east of England," J Public Health (Oxf) 27 (2005): 316-7
6. Royal Society for the Prevention of Accidents. Lighter Evenings: RoSPA summertime briefing. Birmingham, 2005 http://www.rospa.com/roadsafety/info/summertime_briefing.pdf (accessed February 10, 2006)
7. Ferguson, S.A., et al., "Daylight saving time and motor vehicle crashes: the reduction in pedestrian and vehicle occupant fatalities," Am J Public Health 85 (1995): 92-5
8. Coren, S., "Accidental death and the shift to daylight savings time," Percept Motor Skills 83 (1996): 921-2
9. Varughese, J., Allen, R.P., "Fatal accidents following changes in daylight savings time: the American experience," Sleep Med 2 (2001): 31-6
10. U.S. Department of Transportation. The Daylight Saving Time study. A report to Congress. Washington, GPO, 1975. Cited by: L.L. Lawson, Acting Deputy Assistant Secretary for Transportation Policy, appearing before the House Science Committee, Energy Subcommittee, concerning daylight saving time and energy conservation, May 24, 2001 http://www.house.gov/science/energy/may24/lawson.htm (accessed February 10, 2006)
11. Kandel, A., Metz, D., "Effects of Daylight Saving Time on California Electricity Use," California Energy Commission, May 2001 http://www.energy.ca.gov/reports/2001-05-23_400-01-013.PDF (accessed February 10, 2006)
12. Tellier-Beauregard, F., "PRB 05-18E Daylight saving time and energy conservation," Parliamentary Research and Information Service, Parliament of Canada. July 29, 2005 http://www.parl.gc.ca/information/library/PRBpubs/prb0518-e.htm#2txt (accessed February 10, 2006)
13. Olders, H., "Average sunrise time predicts depression prevalence," J Psychosom Res 55 (2003): 99-105
14. Royal Society for the Prevention of Accidents. Single/Double Summer Time: Position Paper. Birmingham, 2003 (updated 2005). http://www.rospa.com/roadsafety/info/summertime_paper.pdf (accessed February 10, 2006)
15. http://whqlibdoc.who.int/publications/2004/9241546123_chap3.pdf (accessed February 10, 2006)
16. Thomas, M.K., et al., "Hypovitaminosis D in medical inpatients," N Engl J Med 338 (1998): 777-83
17. Seasonal Affective Disorder Association http://www.sada.org.uk/ (accessed February 10, 2006)
18. Lahti, T.A., et al., "Transition into daylight saving time influences the fragmentation of the rest-activity cycle," J Circadian Rhythms 19 (2006): 1 [Epub ahead of print]
19. Monk, T.H., Folkard, S., "Adjusting to the changes to and from Daylight Saving Time," Nature 261 (1976): 688-9
20. Bunney, W.E., Bunney, B.G., "Molecular clock genes in man and lower animals: possible implications for circadian abnormalities in depression," Neuropsychopharmacology 22 (2000): 335-45
21. Carskadon, M.A., et al., "Regulation of adolescent sleep: implications for behaviour," Ann N Y Acad Sci 1021 (2004): 276-91

       

           

	EDUCATION Clockwatching       Thomas Mac Mahon (April 2006)
	Ajay Dhakal (April 15th, 2006)       MBBS 3rd year, Kathmandu Medical College ajaydhakal@hotmail.com
	It seems that Day light Saving Time (DST) is paying off well with accident reduction, energy savings and general well being even some people doubt on this. Most of us have experienced that the morning mood is more refreshing than the evening one and work is done more efficiently in the morning than in the afternoon or evening. In a developing country like Nepal, which is still striving for poverty alleviation, education, primary health care and employment, the issues like energy savings and prevention of road traffic accidents are not at the top of the priority list. Thus anything like DST has never been in effect. However for the three winter months the government office hour starts from 9a.m. instead of 10a.m. which is the normal starting time. There have been no significant studies done to show that this rule has done any good in the energy savings, accident prevention and the efficiency of the work delivery. If DST is really efficient in minimizing the expenses of the country by energy savings and maintaining good health of its people then it becomes more relevant for the countries with poor economic performance. So why not start DST even by the developing and under developed nations and see how it works?