AHA: Smoking May Increase Risk of Cognitive Impairment After Coronary Bypass

CHICAGO, Nov. 13 -- Smokers-current and past-are twice as likely to suffer cognitive impairment following coronary artery bypass graft surgery as never-smokers, a researcher reported here.

In a single-center study of bypass patients, those who had a positive smoking history had an odds ratio of 2.04 (95% confidence interval 1.11-3.74, P=0.022), said James P. Slater, M.D., of the Morristown (N.J.) Memorial Hospital/Gagnon Heart Hospital at the American Heart Association meeting here.

A typical case, he said, was a 71-year-old woman who had stopped smoking 20 years before surgery. Three weeks after surgery, she told Dr. Slater that the operation "made me dumber."

As Dr. Slater related, the patient was an avid fan of the New York Times crossword puzzles. The easiest of these appears regularly in the Monday paper and the puzzles increase in difficulty throughout the week, with the Sunday puzzle considered the most difficult. Before surgery, the patient has worked the puzzles every day, but after surgery she said she couldn't solve puzzles beyond Thursday.

Dr. Slater, who discussed his findings at a press conference, hypothesized that smoking may cause damage to the vasculature in the brain.

The study lumped all smoking history together "with no differentiation between current smokers and past smokers."

The stress of surgery, "combined with old injury may explain the cognitive impairment," he said.

The 240 patients were a subset of patients enrolled in a trial of a cerebral oximetry monitoring device, he said. All patients had surgery using the cardiopulmonary bypass, he said, adding that this is "not an on-pump, off-pump issue."

Cognitive testing was conducted before surgery, and again during the first three months following surgery.

A number of studies have suggested that cognitive impairment after bypass surgery is usually temporary, with patients returning to baseline cognitive scores by 12 months. Asked whether these patients had a similar improvement, Dr. Slater said that follow-up has not yet been done, "but I expect that these patients will also improve."

But Dr. Slater added that early cognitive impairment is also "predictive of late impairment, so these patients may have a continued risk."

Robert O. Bonow, M.D., a professor of cardiology at Northwestern Feinberg School of Medicine in Chicago, said that long-term data are needed to truly assess the smoking risk.

"But it is pretty clear that this is more reason not to smoke," he said.