Nobody chooses to have surgery. When people agree to go under the knife, it is usually in an effort to correct a medical condition and improve their quality of life. However, there is evidence that shows some procedures that appear to be successful have actually had negative effects on patients' brains and, as a result, their cognitive abilities.

Healthy heart, troubled brain
After undergoing heart surgery, recovering individuals can experience a number of side effects – many of which affect the brain. For instance, the Cleveland Clinic states that people can feel sad or depressed after leaving the hospital, and even notice a decline in their mental ability.

However, despite the fact that some individuals do not feel as sharp as they did before going under the knife, the Clinic reports that this is normal and the result of serious stress to the body, such as stopping the heart to perform surgery. Regardless of what they experienced, any changes in patients' mental functioning are typically temporary and they should return to their normal state after some time.

Heart surgery may lead to long-term cognitive changes
Following heart surgery, there is always the chance patients may develop delirium. What many may not realize is that this severe case of confusion could lead to long-term cognitive problems. To find out more, researchers from the University of Massachusetts Medical School, Beth Israel Deaconess Medical Center and the Aging Brain Center at Hebrew SeniorLife worked with 225 patients at least 60 years old who were scheduled to undergo heart surgery of some kind.

The results, which appeared in the "New England Journal of Medicine," revealed that in the year following heart surgery, delirium can indeed influence cognitive decline.

"More than half a million heart surgeries are performed each year," said Edward Marcantonio, the study's co-lead author. "Our findings provide important information that might help doctors design interventions to improve the outcomes of older adults undergoing cardiac surgeries."

A possible defense against cognitive impairments
While heart surgery patients may not be able to prevent changes to their brain following their procedures, Canadian researchers found that cognitive training could prove beneficial to individuals who have undergone coronary bypass surgery. If people's memory and attention are targeted, they may be able to lessen the impact of their mental impairments.

"In my opinion, this is a very useful discovery, as it suggests that patients should receive cognitive training in addition to the usual medical follow-up," said Louis Bherer, who worked on the study.

An additional burden for cancer patients
Those who undergo heart surgery are not the only ones who are at risk of developing cognitive problems. Sometimes, specific medical treatments can also have an impact on patients' cognitive abilities.

Livestrong states that many cancer patients also struggle with cognitive changes. In some cases, the mental problems individuals encounter are almost to be expected. For instance, those who have developed a tumor in their central nervous system or received chemotherapy and radiation on the brain may experience changes to their mental ability.

At the same time, chemotherapy and radiation do not have to be administered on the brain for cognitive problems to follow, as Livestrong says changes can also occur after other parts of the body undergo cancer treatment.

Oftentimes, the higher the doses of chemotherapy, the more likely patients are to see a difference in their mental abilities.

Based on this information, individuals who feel healthier than ever following surgery may want to consider taking an IQ test to see if there have been any changes to their cognitive abilities.