In addition to physical exertion, the other common cause of dehydration is alcohol consumption. As a diuretic, alcohol can cause the body to lose up to four times what was consumed while drinking and it can take hours for the body to recover and replenish.
The study published in the journal Medicine & Science in Sports and Exercise looked at looked at 33 different research papers on dehydration.
One found that people performed worse in a range of tests which involved attention span, motor co-ordination and goal-oriented thinking even when they were only 2 per cent dehydrated compared to when they were hydrated.
Another found that females who were only 1 per cent dehydrated made 12 per cent more errors on a quick-thinking game than their hydrated counterparts.
To understand why this may be, a different study carried out functional magnetic resonance imaging (fMRI) scans of the brains of volunteers.
During the scans, the volunteers were asked to carry out a repetitive task designed to mimic those found in industry.
They too found that the dehydrated volunteers made more mistakes than the hydrated volunteers.
They were also able to measure changes in neural firing and showed that when the volunteer was dehydrated the areas in the brain required for doing the task activated more intensely than when they were hydrated.
Interestingly they also saw that when dehydrated other areas of the brain that were not involved in completing the tasks also showed neural activity, implying that the brain might be spending energy on trying to communicate that it was dehydrated.
This dehydration also led to a physical change in the centre of the brain with the fluid-filled spaces called ventricles expanding, which resulted in localised swelling of the brain.
These new insights could help employers to realise the importance of keeping their staff hydrated at work to minimise mistakes and increase focus in the workplace, especially in industries that use machinery in outdoor or high-temperature environments.
We all know that regular breaks are good for us, but perhaps the new message should be to include water consumption in those breaks.
Although the amount of water that we need to drink each day will vary depending on our lifestyle and environment, the National Academies of Science, Engineering and Medicine suggests a daily fluid intake of about 3.7 litres for men and 2.7 litres for women.
The next time you feel like your brain isn't firing on all cylinders, remember that dehydration starts way before you feel thirsty, so keep yourself alert and safe and reach for a glass of water.
