Dr. Wołyńczyk-Gmaj: Science is inconclusive with regard to the effect of time change on health

Recently, the parliamentary administration and the interior committee unanimously endorsed the draft law proposed by the PSL, which assumes no change of time for summer and winter. "Central European Summer Time would be observed during the full year, from October 1, 2018" - explained PSL leader Władysław Kosiniak-Kamysz.

PAP talked about the problem of the influence of time change on the physical and mental health and the answers given on this matter by science with Dr. Dorota Wołyńczyk-Gmaj, psychiatrist, sleep disorders expert.

PAP: What does science say about the effects of time shift on human health?

Dorota Wołyńczyk-Gmaj: If someone expects a clear answer here, then I have bad news: research results are contradictory or mutually exclusive. This is due to the fact that the research is conducted on various groups, in different countries located at different latitudes, and the methodologies of these studies are different. It is difficult to conclusively state how the change affects human health.

PAP: What do these studies look like? Who is studied and at what angle?

DWG: The subject of such studies may be, for example, the effects of time changes on the risk of heart attack. Large national survey of this kind was carried out in Finland in 2001-2009. It was a very large study: more than 6,000 people were surveyed in spring, over 8000 during the autumn time change. It turned out that a few days after the time change there was an increase in the number of infarctions, with the spring change the peak was on Wednesday, and with the autumn change, Thursday was the day of the week with the greatest number of infarctions. Analysis of the whole week after the time change did not indicate a significant increase in coronary events. Similar analyses were conducted for the number of strokes. Finns researched this issue in 2004-2013. However, there was a difference in the conclusions as the increase in strokes - two days after time change in both autumn and spring - occurred only in men. As for the statistics for the whole week, as in the case of infarctions, no significant growth was observed. American studies have shown a greater incidence of both coronary and cerebrovascular incidents. However, these studies were conducted in smaller groups, and their results remain questionable.

PAP: A stroke or heart attack is a serious health event, but can time change negatively affect the life of a theoretically healthy person?

DWG: It undoubtedly affects the quality of sleep. In case of the autumn change, we suffer from difficulty falling asleep, while in the case of the spring change - due to the shorter sleep time. Normally, however, people adapt to the new situation within a few days. Things are worse among people who generally have sleep problems. As individuals very sensitive in this area, they react to time change with very high stress. According to research, this affects primarily neurotic, extroverted individuals. These people, very sensitive when it comes to sleep, also do not handle working in shifts well. People with very distinct chronotypes, "early birds" and "owls", can react less well to time change. The latter have problems with getting up early in the spring, the former do worse in the autumn, because they tend to get up very early.

PAP: Are factors such as mood and cognitive ability also studied?

DWG: Yes, and it turns out that the autums change, or prolonged sleep time, is associated with a brief improvement in mood and cognitive function. But another thing is that this extension of sleep time is not so obvious because it is difficult for people to fall asleep early. Studies have shown that after the autumn change, on Monday and Tuesday children solved mathematical tasks better and had better mood.

PAP: If time change can affect our health or mental state, can it some way affect safety in the broader social dimension?

DWG: For example, there were studies addressing the effect of time changes on car accident statistics. British and Canadian studies have shown a link between time change and an increase in such events, but only in the case of spring change. These studies have also shown that it is important when this time change is made. The closer it was to March 22, the equinox, the better people were able to cope with the effects of changing time. This was related to the fact that the earlier the time change was made, the worse, statistically, the conditions on the road were. The closer to holidays - the larger the traffic, which was also reflected in the statistics. This is a difficult area of ​​research, and due to the multiplicity of factors it is not easy to draw general conclusions. However, in the case of autumn change, no adverse effects were observed, there were even studies that showed that there were less after the change. Here, you also have to take into account the random weather factor during the study period.

PAP: What about suicides? Since for some people time change is a stress factor, does not contribute to suicidal thoughts?

DWG: Reliable studies have not confirmed either increased number of suicides or admissions to psychiatric hospitals. Note that time change from summer to winter or vice versa is nothing compared to jetlag (changing defeating several time zones after a flight - PAP). There is no doubt that the effects of that phenomenon are very harmful to health.

PAP: You mentioned that science does not give a clear answer to the question of the validity of two times in the context of health. However, politicians who make law must make decisions in this regard, and scientific knowledge can and must be a key point of reference. From your point of view, do we have an indication for or against the observance of summer and winter time in Poland?

DWG: Introduction of time change used to be economically beneficial. Today it is probably much less important. As far as the impact on health is concerned, there is no clear evidence that time change is harmful, but since there are doubts, it is not worth the risk.

Daylight saving time is observed in nearly 70 countries around the world, including all European countries except Iceland and Belarus. In 2014, Russia started using Moscow winter throughout the year. In Poland, time change was introduced in the interwar period, and later in 1946-1949 and 1957-1964; it has been observed continuously since 1977. (PAP)

Interview by Jakub Pilarek

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