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Too much sunlight on the head obstructs thinking, study shows

A group of researchers has found that direct and prolonged exposure to sunlight impairs motor and cognitive performances.

Climate Change and Environment

It’s widely known that high temperatures can cause heat exhaustion or heat stroke as the body’s core temperature becomes dangerously high. However, the scorching sun can impact the brain even when body temperature stays normal, a new study shows. Supported by the EU-funded HEAT-SHIELD project, the team that conducted the research suggests that the true effect of prolonged sunlight exposure on human brain temperature and function has not been fully explored in previous research. “Acute exposure did not affect any performance measures, whereas prolonged exposure of the head and neck provoked an elevation of the core temperature by 1 °C and significant impairments of cognitively dominated and motor task performances,” the study published in the journal ‘Scientific Reports’ argues. “Importantly, impairments emerged at considerably lower hyperthermia levels compared to previous experiments,” it adds. Cognition refers to mental abilities and processes involved in acquiring and processing information that are necessary for everyday living. It includes memory, knowledge, attention, reasoning, problem-solving and comprehension. Hyperthermia, even if mild and only briefly occurring, may cause cognitive impairment, adversely affecting attention, memory and the processing of information. “These findings highlight 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 detrimental effects.”

Thermal stress impact

Quoted in a news release by HEAT-SHIELD project coordinator University of Copenhagen, study co-author Prof. Lars Nybo emphasises that “the decline in motor and cognitive performance was observed at 38.5 degrees, which is a 1 degree lower body temperature than previous studies have shown, which is a substantial difference.” Co-author Andreas Flouris, Associate Professor at HEAT-SHIELD project partner University of Thessaly, points to the need to mitigate the health and performance impairments induced by thermal stress that are intensified by global warming. He emphasises that people working or undertaking activities outdoors on a daily basis “should protect their head against sunlight.” He adds: “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.” The researchers conclude that the detrimental effects of solar radiation should be taken into consideration in future studies analysing current weather or climate change effects on occupational health. For the purposes of the study, the researchers tested the mental abilities of 8 men aged 27 to 41 while they worked on computers and were exposed to direct heat exposure from lamps aimed at their head and back. The ongoing HEAT-SHIELD (Integrated inter-sector framework to increase the thermal resilience of European workers in the context of global warming) project addresses the negative effects of workplace heat stress on the health and productivity of workers in five sectors: tourism, agriculture, manufacturing, construction, and transportation. It also looks at the potential rise in these impacts as climate change progresses. For more information, please see: HEAT-SHIELD project website


HEAT-SHIELD, sunlight, cognitive performance, hyperthermia, solar radiation

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