VitalSTATS

STATS Awards the Press a “Purple Heart” on Coronary Bypass Study

by Howard Fienberg
April 2001

“Fix Your Heart and Kill Your Brain: Surgery Worse Than Stroke.” Expected coverage of a new study of some possible dangers in coronary bypass surgery could have been capped by this fictional headline. Instead, while some headlines were similarly scary (“Memory, Thought Problems Follow Bypass, Study Finds,” Baltimore Sun; “Bypass May Permanently Sap Brain Power,” Boston Herald), the content of media coverage was refreshingly careful. Most reports of the complicated findings noted the study’s flaws and de-emphasized the easy, headline-grabbing conclusion: that coronary artery bypass grafting (CABG) leaves many patients with long-term mental difficulties.

The study, published in the February 8th New England Journal of Medicine (NEJM), examined patients who had CABG between 1989 and 1993. Cognitive testing found mental decline in 53 percent of the patients when discharged from the hospital; 36 percent after six weeks; 24 percent after six months; and 42 percent five years later. The researchers found that cognitive decline at time of discharge was a significant predictor of long-term decline. While previous research had found cognitive decline a problem for as many as 3/4 of patients at discharge and 1/3 six months later, little data was available on long-term decline. Therefore, the results, while startling, were also tentative.

An accompanying NEJM editorial criticized the study, noting that the later decline in bypass surgery patients could be related to the aging process. More importantly, the editorial faulted the lack of any control group against which to compare cognitive functions. Without a control group, deciding on “normal” cognitive functions would be difficult, as would be isolating the effect of the operation and “how much might relate to such factors as a patient’s condition prior to surgery” (The Wall Street Journal). The NEJM editorial pointed out that other recent findings indicate “that postoperative cognitive dysfunction... may persist for up to two years in approximately 10 percent of patients, even after non-cardiac surgery.” A majority of media reports stressed such flaws.

Even so, no reports addressed another problem, raised in a letter to the editor of The Wall Street Journal (Feb. 22). Lawrence H. Cohn of Harvard Medical School pointed out that a third of the patients in the study were lost to follow-up. Lacking the cognitive test scores on so many of the original sample weakens the veracity of the end results.

The bulk of journalists wisely discounted the simplistic conclusion which could have been drawn from the NEJM study – that CABG itself was to blame. As study co-author Olga Selnes told the Baltimore Sun, “We can’t be sure that it’s due only to bypass.” The Associated Press interviewed Dr. Irving L. Kron of the University of Virginia School of Medicine, who observed that patients in the study could have lost cognitive ability anyway. “It may be that the stress of the operation brings things out or pushes things along that were there to start with,” he told the AP. Indeed, most reports focused on possible causes related to anesthesia, surgical instruments and surgery in general (not just CABG).

Unfortunately, while most reports delved into possible factors emanating from surgery, few clearly addressed another possible factor – coronary artery disease itself. Kudos to the Baltimore Sun for highlighting that “patients who have bypass surgery might also have problems in the blood vessels of their brains.” Even they could have put it even more bluntly: patients suffering from coronary artery disease might also suffer from cerebrovascular disease, a condition unrelated to surgery.

This is not to criticize journalists who covered the study. The NEJM study was striking but complex, laced with numerous temptations for tabloid reporting. In the end, most reports specifically emphasized that the findings should not discourage people from undergoing CABG and that the risks of the disease outweighed possible risks in the treatment.


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