NEW YORK (CBS 2) — We’ve always thought exercising your brain is just as important as exercising your body, but new research shows in some cases it may actually be harmful.

CBS 2’s Dr. Holly Phillips delved into the study and found out what it means for all of us.

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Carmen Cox has a good memory and so the 71-year-old is taking classes at a neurological institute to keep her mind sharp.

“I am aware that as you get older, you do lose your memory and I would like to prevent it as much as possible,” Cox said.

Whether it is brain exercises, computer games or doing a crossword puzzle, research has shown that seniors who keep their mind active can delay the onset of Alzheimer’s Disease.

However, a new study in the journal Neurology indicates once Alzheimer’s hits, those brain exercises might do more harm than good.

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Researchers followed two groups of patients and as expected, those who kept mentally sharp were able to delay Alzheimer’s.

But then a surprise — once the disease took hold, patients in the active group saw their brain function deteriorate faster, Phillips reported.

“Once people got dementia it seemed to have the opposite effect. That more mental stimulation seemed to be worse,” Psychiatrist Gary Small said.

Researchers speculate the brain is like a muscle. Exercise can make it stronger, but once it’s compromised, exercise may actually make it worse.

“Mental stimulation sped up brain decline at a certain point,” Small said.

Experts say even if that is true, people who don’t have dementia should continue to exercise their brains.

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And with five million Americans currently battling the illness, anything to prevent it from affecting others matters.