New research has found a link between delirium and a decline in mental abilities in people who undergo heart surgery.

Delirium is a state of confusion that occurs after a surgery, infection or an illness. Delirium is common and affects 15 to 60 percent of U.S. patients.

The study included more than 200 people who underwent cardiac surgeries. Researchers found that people who didn't develop delirium post-surgery recovered faster than the patients who developed delirium. Their cognitive function was higher than others.

"Our findings now suggest that postoperative delirium, once thought of as an acute, transient cognitive disorder, may have longer-term effects on cognitive function in patients undergoing cardiac surgery," said co-lead author Jane Saczynski, assistant professor of medicine at the University of Massachusetts Medical School.

The patients were followed for months after the surgery. People who developed delirium took almost 6 months to reach their pre-operative cognitive functions.

The study suggests that preventing delirium might help patients recover faster and function normally after the surgery.

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

According to researchers, rehabilitation facilities can be extended to people who are at an increased risk of developing cognitive decline.

"Since patients who experience delirium continue to show improvement in cognitive function six months after surgery, extending additional rehabilitation services to these patients may have added benefits," said co-senior author Richard N. Jones, director of mental health and aging at Hebrew SeniorLife and assistant professor of medicine at Harvard Medical School.

Earlier research says that taking statins before surgery helps in reducing risk of developing delirium. Another study suggests that major depression is associated with development of delirium post cardiac surgery.

The study is published in the New England Journal of Medicine.