With the arrival of July, the temperature has risen and more outdoor swarms have increased. Go to the beach to sunbathe, go to the park with a large lawn and the whole family have a picnic, such life think all feel beautiful. However, a new study from the University of Copenhagen shows that wearing a hat when exercising for long outdoor exercises during the summer, and exposing your scalp directly to the sun, are potentially damaging brain function.
While the findings may sound scary, the researchers’ starting point for the study is well-documented. About half of the world’s population lives in areas where extreme or cold weather conditions are likely, and the thermal effects of the environment potentially affect people’s lives. In the outdoor environment, when the person’s head is exposed to solar radiation, will produce a considerable thermal load, researchers through this study confirmed that such conditions are really harmful to human health.
How does the brain dissipate heat when heat accumulates?
Human brain function is highly dependent on a stable supply of glucose and oxygen in the blood, but the brain is also highly vulnerable to damage when conditions that maintain a steady state of heat in the brain change. The brain is highly isolated by being sealed in the skull, but the brain must remove the heat generated by metabolism to maintain the temperature of the brain. In general, the brain distributes heat mainly through the flow of arterial blood. In a state of rest, 700 milliliters of blood per minute can take away 1 kilojoule of energy, which will help the brain reduce by 0.3 degrees Celsius.
Sunlight can penetrate the skin a few millimeters and heat the tissue sunder it, so exposing your head directly to intense solar radiation for long periods of time could theoretically raise the temperature of the brain. In high temperature environment, a large amount of sweating will consume the body’s water and salt, leading to dehydration, and reduced body fluids and salt directly lead to insufficient blood supply to the brain. As a result, the brain’s ability to dissipate heat through blood circulation is greatly diminished. In addition, special layered structures in the skull and cranial cavity similar to insulation cups can greatly limit the passage of heat, which causes the brain to dissipate heat even worse.
Blood flow in the brain helps the brain dissipate (Photo: University of Southern California)
Not only affects heat dissipation, sunlight radiation also affects motor cognitive function
Is the intense sunlight really affecting brain function and brain temperature, let’s work with the researchers to find out exactly what.
Eight healthy men who took part in the study drank enough water and abstained from alcohol and vigorous exercise 24 hours before any experiments. As shown in the figure below, the researchers simulated exposure to intense sunlight (about 1,000 watts per square meter) in the lab to test the subjects’ motor cognition. The test is divided into four main areas:
Simple motion task (testing pinching/adjusting force based on the numbers prompted on the screen).
Simple cognitive tasks (four numbers are displayed on the monitor, and participants use the numeric keypad to calculate and type the sum of the four numbers).
Combine the motor cognition task (add calculationbased based on the four numbers on the screen, then type the results and test the thumb and index finger kneading/adjustment force).
Complex visual motion tracking tasks (complete tasks with a pinching force with the cursor, simultaneously calculating the sum of numbers, typing results, and using thumb and index finger kneading/adjustment forces through the strain gauge sensor).
Simulated solar radiation schematics. Head radiation includes not only a lamp above but also the head and neck.
The figure below shows a significant decrease in the scores of subjects who were exposed to simulated sunlight for long periods of time (2 hours) for complex exercises and integrated motor cognition tasks. In contrast, acute exposure (15 minutes) or continuous lower body heating did not lead to a decline in motor cognitive ability.
Not only affects heat dissipation, sunlight radiation may also cause damage to the brain nerve
The researchers found that prolonged exposure of the head and neck in sunlight resulted in an increase of 1 degree Celsius in the body’s core temperature (the body temperature measured by the rectal thermometer when it was inserted into the sphincter about 10cm), which clearly had a considerable negative impact on the normal maintenance of the body’s function.
In addition, to further study the effects of sunlight radiation on the brain nerve, the researchers tested the subjects’ auditory induced potentials in the brain stem. What is the brain stem auditory induced potential? Let’s first explain what the auditory pathway is. As shown below, the sound waves felt in the outer and middle ears of our ears are transmitted to the inner ear, where the cochlear implants are converted into bioelectric signals and then passed all the way through the hearing nerve to the cerebral cortex before people can hear the sound.
Hearing to the path (Image Source: Baidu Encyclopedia)
The auditory-induced potential of the brain stem is an objective indicator of the damage to the brain stem. The instrument records the potential reactions of the cochlear implants and hearings within 18 milliseconds of sound, and then reflects the functional status of the cochlea-brain-related structure. Any lesions or impairments that affect the auditory pathways can affect this indicator.
The auditory brain stem-induced potential can objectively and sensitively reflect the function of the central nervous system, and it has changed when the brain stem is slightly damaged and clinically asymptomatic and signs are. The study, by measuring this indicator, found that when simulated sunlight radiation was applied for a long time (about 2 hours, until the core temperature increased by 1 degree), the subject’s brain stem hearing-induced potential changed, while in acute (15 minutes) exposure to sunlight radiation, no signs of impact were shown.
Not only that, the long period of direct sunlight in the simulated state has also significantly changed the physiological and psychological indicators. This increased the subject’s heart rate per minute from 76 jumps to 116 jumps, increased the body core temperature by 1 degree, and the average skin temperature increased by 2.3 degrees Celsius, especially at the pillow bone, the head and neck skin temperature measured increased by as much as 5.4 degrees. These data clearly mean that subjects will experience a strong feeling of discomfort.
Overall, the study found that prolonged radiation heat applied to the head affected brain function to some extent, especially in complex motor and combined motor cognition tests, in which subjects showed significant attenuation. Direct exposure to radiant heat in the head and neck mainly affects the shallow part of the brain. But even just a superficial increase in temperature in the brain can damage the short-term ability of the brain. For contrast, radiation exposure to the current body causes a similar increase in the body’s deep core temperature, which does not cause significant damage. In addition, short-term acute exposure to the head and neck immediately raises the temperature outside the cranial (skin), but does not have a significant effect on brain function.
Does it mean that the summer can not “skinhead” happy to play?
We often say that today’s sun is poisonous, the human sun shell straight pain. Judging from the conclusion of this latest study, this sentence is more than an exaggeration. Moreover, the brain shell pain is small, the brain child problem can be quite serious.
However, given that the sample size of the study (8) is far from statistically significant, the conclusions, while chilling, are not at odds with life’s common sense. Everyone knows that the sun for a long time, the head does not hurt also have great possibility of heat stroke. There are many recent studies like this, and the media tend to over-interpret the study itself in order to attract attention, and we don’t listen to these statements. Of course, while it’s no fuss, pay attention to sun protection, avoid heat stroke or completely reliable “health” advice in the hot summer months.
There are a lot of outdoor workers who are exposed to high heat seasonally, which does have an impact on their health and work. For this kind of special population, the use of various forms of hat to shade the sun can be a good way to reduce radiation exposure to the body caused by heat damage. However, when using a hard hat such as a hard hat, you may also increase thermal damage due to limited cooling capacity. Therefore, such personnel should ensure adequate drinking water and adequate rest, to avoid long-term work in the hot sun, so as not to cause a short decline in brain function caused by safety accidents.
Hot summer, enjoy the sun is good, do a good job of sun protection is more important.