Every year in spring the clock time (daylight saving time) is changed for economic reasons: energy saving (daylight saving time).
The hands of the clock move on the last Sunday of March and, at the end of summer, the last Sunday of October: first forward losing an hour of sleep but gaining an hour of light, and then the opposite at the end of the day. ‘summer, the hands are moved backwards, gaining an hour of sleep and light (it gets light later, it is useless to wake up earlier and use the electricity).
This time change also takes the name of summer time for the period of the year in which the movement of the hands occurs.
In other parts of the world the dates change a bit, for example March 9 in Canada, the second Sunday in March and the first Sunday in November in the United States, but the result is the same. When the time coincides with that of the reference time zone, it is called solar time , and in general it is winter time.
The need to save diesel during the First World War had led to the birth of summer time in Europe, in 1916 in Italy. With ups and downs in Italy and definitively entered into force with a law of the 1960s due to the energy crisis [1, 2, 3, 4].
In Europeit is currently adopted by all Member States, including Switzerland. Instead Russia (followed by Belarus) in 2011 decided to adopt only the summer time because the solar one would have been a cause of stress, not without internal controversy [5].
(source Wikipedia [1])
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- The states that adopt the hour change are in blue.
- States that have used the time change in the past are shown in orange.
- States in which there has never been a change of time are in red.
The European Parliament, after a public consultation which took place between July and August 2018 and 84% of the votes in favor, approved the abolition of the obligation for the various member countries to pass from one hour to the next twice a day. year and each state will have to decide by 2021 whether to adopt summer time or solar time forever.
The shift of the time reflecting the natural lengthening and shortening of the days, would allow you not to wake up earlier with the light in the morning in the summer and to turn on the bulbs later after sunset with a consequent energy saving.
“The idea is to have people up and about during the longer daylight hours, to save energy and increase productivity” writes the New York Times [4].
Increases productivity
What happens to the body when the time is changed The time
change is called summer time because it is artificially imposed and does not follow the course of the natural hours. It is known that living organisms use sunlight to be able to live and to synchronize numerous biological functions and thus allow life on earth as and for millions of years.
In our body there are neurochemical and hormonal functions that follow the sunlight, synchronizing the sleep-wake cycle and regulating the functioning of a whole series of automatic functions.
Artificially changing these natural rhythms has an impact on the body
The scholars who have dealt with the subject do not have univocal points of view. If we consider the energy plan it is clear that there is an energy saving but it is also necessary to take into consideration the effects on human activity to evaluate if the energy saving is not nullified by the negative effects on health.
In this respect, there is still no unanimous agreement. On the one hand, there are those who support the positive effects of the change of time with research that has highlighted a reduction in the number of road accidents [6, 7, 8] and at work [9, 10]. Even if the results remain uncertain [11].
On the other hand, there are scholars who evaluate the negative aspects on human health. A quarter of the world population is exposed to artificially changing the time twice a year [12]. Among these people exposed to daylight saving time, in a numerically ill-defined number of scholars have found adaptation alterations because daylight saving time and normal solar change due to the seasons do not coincide with consequent destruction of natural human adaptation to natural light (desynchronization) and probably with alterations of other biological parameters that depend on light and seasons [12].
It is not unusual to hear people complain about the change of time, complain of tiredness, nervousness, and the presence of unpleasant symptoms related to the change in the rhythms of the sleep-wake cycle (difficulty in sleeping) with difficulty in adapting to the new time and consequently less productivity, for a period of time ranging from a few days to several months.
In people who already naturally suffer from a seasonal disorder linked to the change in the length of the days (that is, who have more difficulty in adapting to the natural rhythm of the seasons), they could manifest themselves in addition to the alterations of the circadian rhythm with the increase of insomnia problems, even real mood disorders which in the Nordic countries are known asseasonal affective disorders ( SAD from the English synonym “ seasonal affective disorders ”). But this deserves a separate post.
The increase in sleep fragmentation and sleep latency represent a cumulative effect on sleep loss at least the following week or even weeks following the time change, if not sometimes longer [13]. The change in the fall also suggests a net loss of sleep for at least a week [13].
Indirect evidence demonstrates an increase in the rate of traffic accidents and in health-related behavioral changes that may be related to sleep disturbance, suggesting that adaptation to time change is neither immediate nor without consequences [13]. These results agree with previous studies which suggested that humans are sensitive to even small changes in circadian rhythms [14].
Changes in the markets on the Monday following the change of time have also been hypothesized but the studies are conflicting [15, 16] while it seems that the change of time has negative repercussions on habits in exercising physical activity in a portion of the population in general to a reduction in physical activity itself [17]
Sleep scholars still insist that there may be alterations in cognitive performance and therefore also in academic performance, so much so as to advise against exams in the week immediately following the change of time [18].
Some researchers have gone further noting an increase in other health problems such as myocardial accidents (heart attack) although not all scholars agree with these aspects [19, 20].
In conclusion, the effect on human health of these changes from now on is not yet well defined, even if we can intuitively think that they are not completely harmless. On the other hand, the use of electric current and consequently the possibility of artificially altering the sleep-wake cycle has led some scholars to hypothesize the increase in the incidence of some minor and major disorders from simple insomnia to anxiety disorders and mood (depression and bipolar disorder) that some of us would be more sensitive to than others.
Sources
[1] https://it.wikipedia.org/wiki/Ora_legale
[2] https://en.wikipedia.org/wiki/Summer_time_in_Europe
[3] https://en.wikipedia.org/wiki/Daylight_saving_time_by_country
[ 4] https://en.wikipedia.org/wiki/Summer_time_in_Europe
[5] https://latitude.blogs.nytimes.com/2012/10/01/will-russia-restore-daylight-saving-time/
ref=daylightsavingtime
[6] Huang A, Levinson D. The effects of daylight saving time on vehicle crashes in Minnesota. J Safety Res, 2010; 41 (6): 513-20.
[7] Lahti T, Nysten E, Haukka J, Sulander P, Partonen T. Daylight saving time transition and road traffic accidents. J Environ Public Health, 2010; 2010: 657167.
[8] Feguson SA, Preusser DF, Lund AK, Zador PL, and Ulmer RG. Daylight saving time and motor vehicle crashes: the reduction in pedestrian and vehicle occupant fatalities. Am J Public Health. 1995; 85 (1): 92–95.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1615292/pdf/amjph00439-0094.pdf
[9] Lahti T, Sysi-Aho J, Haukka J, Partonen T. Work-related accidents and daylight saving time in Finland. Occup Med (Lond). 2011; 61 (1): 26-8.
[10] Morrassaei S, Smith PM. Switching to daylight saving time and work injuries in Ontario, Canada: 1993-2007. Occup Environ Med, 2010; 67 (12): 878-80.
[11] Barnes CM, Wagner DT. Changing to daylight saving time cuts into sleep and increases workplace injuries. J Appl Psychol, 2009; 94 (5): 1305-17.
[12] Kantermann T, Juda M, Merrow M, Roenneberg T. The human circadian clock’s seasonal adjustment is disrupted by daylight saving time. Curr Biology, 2007; 20; 17 (22): 1996-2000.
http://cbn.eldoc.ub.rug.nl/FILES/root/2007/CurrBiolKantermann/2007CurrBiolKantermann.pdf
[13] Harrison Y. The impact of daylight saving time on sleep and related behaviours. Sleep Med Rev, 2013; S1087-0792 (12) 00114-1. https://pubmed.ncbi.nlm.nih.gov/23477947/
[14] Burgess HJ, Legasto CS, Fogg LF, Smith MR. Can small shifts in circadian phase affect performance
Appl Ergon. 2013; 44 (1): 109-11. https://pubmed.ncbi.nlm.nih.gov/22695081/
[15] Berument H, Dogan N. Effects of daylight saving time changes on stock market volatility: a reply. Psychol Rep, 2011; 109 (3): 863-78.
[16] Kamstra MJ, Kramer LA, Levi MD. Effects of daylight-saving time changes on stock market volatility: a comment. Psychol Rep, 2010; 107 (3): 877-87.
[17] Rosemberg M, Wood L. The power of policy to influence behavior change: daylight saving and its effect on physical activity. Aust N Z J Public Health, 2010; 34 (1): 83-8.
[18] Schneider AM, Randler C. Daytime sleepiness during transition into daylight time in adolescent: are owls higher at risk
Slepp Med, 2009; 10 (9): 1047-50.
[19] Janszky I, Ljung R. Shifts to and from daylight saving time and incidence of myocardial infarction. N Engl J Med 2008 Oct 30;359(18):1966-8. https://www.nejm.org/doi/pdf/10.1056/NEJMc0807104
[20] Janszky I, Ahnve S, Ljung R, Mukamal KJ, Wallentin L, Stenestrand U. Daylight saving time shifts and incidence of acute myocardial infarction–Swedish Register of Information and Knowledge About Swedish Heart Intensive Care Admissions (RIKS-HIA). Sleep Med, 2012; 13 (3): 237-42. https://pubmed.ncbi.nlm.nih.gov/22285108/
