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Too Much Sun to Head, Heat Stress Said to Affect Cognition

A new Danish-led study reveals the harmful cognitive effects of prolonged sunlight exposure to the head. The findings, published in the journal Scientific Reports, suggest that people working or engaging in daily activities outside should take precaution to protect their head against sunlight.

“The novelty of the study is that we provide evidence that direct exposure to sunlight — especially to the head — impairs motor and cognitive performance,” said professor Dr. Lars Nybo, the project coordinator from Department of Nutrition, Exercise and Sports at the University of Copenhagen in Denmark.

“Adding to this, the decline in motor and cognitive performance was observed at 38.5 degrees Celsius (101 degrees Fahrenheit), which is a 1 degree lower body temperature than previous studies have shown, which is a substantial difference.”

Around half of the world’s population live in regions where heat stress is an issue that affects the ability to live healthy and productive lives. It is well known that working in hot conditions, and the associated hyperthermia (rise in body temperature), may reduce one’s ability to perform physically demanding manual work.

However, the effects on cognitively dominated functions, and specifically the influence from sunlight exposure on human brain temperature and function, have not been studied.

Previous research on this topic has been conducted primarily in the laboratory, without accounting for the marked effect that sun radiation may have — in particular, when the head is exposed for a prolonged period of time.

Many workers in agriculture, construction and transport are at risk from being affected by exposure to strong sunlight. Postdoc Dr. Jacob Piil and Nybo from the University of Copenhagen conducted this study in collaboration with colleagues from Thessaly University in Greece. They are convinced that the findings have implications not only for the workers’ health, but also for their work performance and safety.

“Health and performance impairments provoked by thermal stress are societal challenges intensifying with global warming and that is a prolonged problem we must try to mitigate,” says associate professor Andreas Flouris from FAME Laboratory in Greece.

“But we must also adapt solution to prevent the current negative effects when workers are exposed, and this study emphasize that it is of great importance that people working or undertaking daily activities outside should protect their head against sunlight.”

“The ability to maintain concentration and avoid attenuation of motor-cognitive performance is certainly of relevance for work and traffic safety as well as for minimizing the risks of making mistakes during other daily tasks.”

Overall, the findings suggest that science may have underestimated the true impact of heat stress, for example during a heat wave, as solar radiation has not been studied before. Future studies should incorporate sunlight, as this seems to have a selective effect on the head and the brain.

The study highlights the importance of including the effect of sunlight radiative heating of the head and neck in future scientific evaluations of environmental heat stress impacts, and specific protection of the head to minimize harmful effects.

The study involved eight healthy, active males (ages 27 to 41). The motor-cognitive test consisted of four different computer math and logical tasks that relied on fine motor precision. Four lamps were positioned to radiate either on the lower-body or on the head (back, sides and top, to avoid blinding the participants).

Source: Faculty of Science- University of Copenhagen



Too Much Sun to Head, Heat Stress Said to Affect Cognition

Traci Pedersen

Traci Pedersen is a professional writer with over a decade of experience. Her work consists of writing for both print and online publishers in a variety of genres including science chapter books, college and career articles, and elementary school curriculum.

APA Reference
Pedersen, T. (2020). Too Much Sun to Head, Heat Stress Said to Affect Cognition. Psych Central. Retrieved on December 3, 2020, from
Scientifically Reviewed
Last updated: 8 Jul 2020 (Originally: 8 Jul 2020)
Last reviewed: By a member of our scientific advisory board on 8 Jul 2020
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