Can Dehydration Affect Memory?

Can Dehydration Affect Memory?

After finishing a very hot marathon, one reader has concerns about whether it caused some memory problems.

Kristen asks: Can dehydration and hyperthermia have effects (short term or long term) on memory? I ran a marathon a few weeks ago, and the heat posed a big challenge for me. I finished but ended up in the urgent care later. The doctor diagnosed me with dehydration and hyperthermia.

Since then I’ve felt like my memory has been off and I have to work a little harder to remember things that were second nature. I get distracted easily, have a hard time focusing, my thoughts get jumbled and I lose my train of thought if interrupted. I’m 28 years old and bounced back very quickly from my first marathon two years ago, but heat was not an issue.

The short answer is that heat-related problems can cause damage to brain tissue, just like a concussion. But without knowing some of the details of your “finish condition”, like your immediate post-race rectal temperature, your serum sodium measurements and other blood parameters, as well as your pre- and post-race weights, it’s hard to make an accurate diagnosis of what went wrong. It was a “hot” race and there were a number of people treated for exertional heat stroke at the finish line.

You could have been dehydrated (or you could have been over hydrated, as it is not uncommon to drink too much when it is hotter than you expected).

We  know that athletes are cognitively slower when dehydrated – this has been tested in lab conditions, but those effects usually disappear once hydration is restored. We also know that hyponatraemia (low sodium levels that can cause brain swelling) as well as hypoglycemia (low sugar levels that can cause an energy deficit) can produce brain changes that lead to mild memory and cognitive changes like the ones you describe. However, they also generally go away with time.

If you are not recovered a few weeks out from your race, you should definitely see your personal physician.


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