Dehydration can affect cognitive function
Researchers from the Georgia Institute of Technology reviewed 6,591 studies on hydration and found that functions including attention, co-ordination and problem solving are diminished by dehydration. The researchers focused on acute dehydration, which can be caused by heat, not drinking enough or exertion. As opposed to chronic dehydration which can be caused by disease or disorders.
The review published in the journal Medicine & Science in Sports & Exercise found that older people are more susceptible to dehydration as they often lose their sensation of thirst and with age some individuals find their kidneys are less able to concentrate urine, meaning they maintain less fluid. Individuals with high body fat also have lower relative water reserves than lean individuals.