Teenage brains shrink for lack of water


Teenagers taking GCSE’s or A-Levels over consecutive days could see performance significantly affected if they don’t drink enough fluids, according to hydration experts.

It only takes 1% dehydration by weight to impact short-term memory by 13%

Water for Work and Home is warning parents and teachers that they must ensure students are properly hydrated as they face the onslaught of the exam season.  

Ben McGannan, MD of the company that conducted the study, said: “There appears to be a very inconsistent approach to the provision of drinking water facilities across UK schools and colleges and in exam halls.”

Medical research looked at the dehydration affects on brain structure and function in healthy adolescents.  The results of the study identified that hydration needs to be a major issue for adolescents, their parents and, crucially, their schools. 

In particular the study identified that significant negative effects of dehydration with structural changes in the brain equated to the same level of shrinkage expected in Alzheimers’ patients over a two and half month period, or 14 months of ageing in otherwise healthy individuals. 

Mr McGannan said: “We have huge sympathy with schools and 6th form colleges that are struggling to manage resources on limited funds.  There also appears to be limited general guidance on this issue. But we feel it is crucial that drinking water is readily available for students throughout the school day and, especially, during exam time. 

"Whilst students may be able to tackle one exam a day when dehydrated, if they have several exams to take on the same day, lack of regular access to drinking water could have a seriously detrimental affect on their results.”

The study investigated the impact of dehydration on brain function, using functional magnetic resonance imaging (fMRI) in 10 healthy adolescents.  Each subject completed a series of exercises which resulted in dehydration.  They were then tested for their cognitive performance.   

The study found that dehydration following the exercises led to a marked increase in fronto-parietal brain areas necessary to perform an executive function task (Tower of London) compared to a control condition.  Cerebral perfusion during rest was not affected. The increase in response after dehydration was not paralleled by a change in cognitive performance, suggesting an inefficient use of brain metabolic activity following dehydration.

This pattern indicates that dehydrated participants exerted a much higher level of neuronal activity in order to achieve the same performance level. Given the limited availability of brain metabolic resources, these findings suggest that prolonged states of reduced water intake may adversely impact executive functions such as planning and visuo-spatial processing.

Professor Gemma Calvert, Chair of Applied Neuroimaging at the University of Warwick, said: “Given that there isn’t always any immediately observable effect on function from dehydration, we are therefore particularly concerned about the possible longer term effects on individuals who aren’t sufficiently hydrated.

"Just because you can’t tell that someone is dehydrated from their behaviour that doesn’t mean their brain and body aren’t immune to the effects.

“The research identified that reaction times in the acutely dehydrated were no worse than those not dehydrated, when looking at immediate short-term effects. But, crucially, it showed significant negative effects of dehydration with structural changes in the brain that equated to the same level of shrinkage expected in Alzheimer’s patients over a two and half month period, or 14 months of ageing in otherwise healthy individuals.

“In particular, an increase in neuronal activity required to perform a complex thinking task was detected in the acutely dehydrated, compared to the non-dehydrated, which suggests that the human brain compensates for dehydration by working harder.  But given the frugal nature of brain function, it seems unlikely that such effort could be sustained and, as a result, there could be a decline in performance over the working day.”  

*Dehydration Affects Brain Structure and Function in Healthy Adolescents has been published in Human Brain Mapping, 2010.

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