Those who start work earlier express more discomfort with the seasonal time change. This is the main conclusion of a study that the lecturers at the University of Santiago de Compostela (USC) and the University of Seville (US), Jorge Mira Pérez and José María Martín Olalla, have just published in the journal Chronobiology International, in which they analyse in detail the results of the public consultation organised by the European Commission in 2018 in the then 28 member states, which obtained 4 million responses.

The study shows that the rate of responses against the current regulation was higher as the latitude of the country was higher. To explain this result, Martín Olalla and Mira, who have just published a study in the Royal Society journal Open Science, which has been referenced by Science magazine, compare the rates against the time change with the time of the start of work activity and show that earlier activity starts resulted in a higher rate of people against the current regulation. “The public consultation was treated as if it were a survey, highlighting the balance of responses for and against changing the clocks. We treated it as a natural experiment and studied how those who said ‘no’ (or ‘yes’) were distributed,” stresses Jorge Mira. “On average, 0.5% of the country’s population responded to the public consultation; it is too small a rate to predict the outcome of a hypothetical referendum on changing the clocks, but it is more than enough to carry out an observational study and analyse what stimuli influenced people to vote for or against the current mechanism,” stresses Martín Olalla.

The authors explain that the regulation covering the changing of the clocks aims to align the start of work with the sunrise. That is why in their calculations they use the distance between the start of work and the winter sunrise, which gives an idea of the light conditions at that time. “Nuance is key. When we use the time at which work begins we do not find significant correlations with the public consultation, but when we analyse the distance from the start time to the winter sunrise, then we do see that countries with earlier start times have higher rates against,” says Martín Olalla. “This result cannot be explained if, as usual, changing the clocks is related to time zone or geographical longitude; it only makes sense when changing the clocks is seen as a response that is physiologically modulated,” stresses Mira.

The study suggests that the current regulation acts as a compromise between those who start earlier, and therefore are more uncomfortable and would be more disadvantaged by a permanent summer time, and those who start later, who are more comfortable with the current situation but would be more disadvantaged by a permanent winter time.