What should we believe?

News about health deluges us daily: On the nightly news, in the newspaper, on blogs, and even at parties, we hear pronouncements about what to eat, what pill to take, which screening test we absolutely must schedule—or might be better off avoiding. And what’s recommended one day seems laughable the next. So what health news should we heed? What should we ignore?

Most of us lack the tools to judge, said Michael B. Bracken, M.P.H. ’70, Ph.D. ’74, the Susan Dwight Bliss Professor of Epidemiology at the School of Public Health. “We don’t educate children and adults in anything to do with understanding risk or probability,” Bracken said in a recent interview.

Bracken offers a remedy in his new book, Risk, Chance, and Causation: Investigating the Origins and Treatment of Disease. In this accessible, lively, and often witty book, Bracken explains how epidemiologists understand the world. He shows why good study design is crucial in distinguishing between chance and causation. Bracken discusses the reasoning behind ethical guidelines and, surprisingly, explains how they can sometimes cause harm. In “Celebrity Trumps Science,” Bracken cites a rock star’s misinformation about the effects of marijuana and an ex-Playboy bunny’s inaccuracies about the cause of autism.

In addition, Bracken devotes a chapter to the benefits and the limitations of using animals for research—animals often fail as proxies for human beings. For example, a potential leukemia drug worked well in monkeys but nearly killed six healthy humans.

Bracken lays out the principles of a good study by describing one from China that tested whether women who examined their breasts for lumps reduced their chance of dying from breast cancer. The study enlisted 250,000 women and compared a study group (women taught self-examination) with a control group (women not instructed in self-exam). All were Shanghai textile workers living similar lifestyles, which minimized influences of other variables. The 10-year study found that the women trained in self-exam found more breast lumps than the controls did, but deaths from breast cancer were identical in both groups.

An example from Bracken’s own research on the effects of early childhood illness on later chronic disease illustrates the complexity of study design. Does giving antibiotics to very young children make them more likely to develop asthma? Antibiotics might limit the development of the child’s immune system. On the other hand, children prone to asthma may get more antibiotics because they wheeze. Even careful study design could not totally eliminate uncertainties about which came first: the antibiotics or the asthma.

The deluge of health news will remain relentless, he said. “The 24-hour news cycle has to be continually fed. They jump on everything.” Unless people learn how to evaluate news on their own, he said, “the net effect will be that the real health messages get lost in this quagmire of misinformation.”

Ed. Note: In February we learned that Risk, Chance, and Causation: Investigating the Origins and Treatment of Disease had been selected as a a Choice Outstanding Academic Title for 2013 in the Health Sciences Category, and received an Honorable Mention for the 2013 American Publishers Awards for Professional and Scholarly Excellence in the economics category.