According to Anne McTiernan, a cancer prevention researcher at Seattle’s Fred Hutchinson Cancer Research Center, the equivalent of a small glass of wine, an eight-ounce beer or one ounce of hard liquor is associated with a 5 percent increased risk of breast cancer in premenopausal women and a 9 percent increase in postmenopausal women, as discussed a few weeks ago here.
Many women obsess over their risk for breast cancer. Which is why news media often flash provocative headlines whenever a study suggests a link between breast cancer and an “exposure” or “risk.”
The news of increased risk due to wine and alcohol consumption, from the renowned Fred Hutchinson Cancer Research Center in Seattle, set off the usual alarms. But it also raises more questions.
Questions of how best to interpret this “increased risk” finding within the appropriate context.
Helping in this process is a new book, “Making Sense of Science: Separating Substance from Spin,” by New York Times science writer Cornelia Dean. The author seeks to help non-scientists evaluate scientific claims, with attention paid to studies related to health.
“People who want to scare us typically give us relative risk figures,” Dean writes. Raising a risk that starts off small can result in a risk that’s higher but still very small in absolute terms. This is best shown in an example. “Something that raises your risk of heart attack by 30 percent [relative risk],” she explains, “could be no scarier than raising your odds from 6 in 1,000 to 8 in 1,000 [absolute risk].”
Back to the “increased risk due to wine consumption” announced in May, when we hear that a small glass of wine a day may raise a premenopausal woman’s breast cancer risk by 5 percent and a postmenopausal woman’s by 9 percent, remember, these numbers portray relative risk. Instead, what we need to know is absolute risk.
“We know drinking modestly raises the risk of breast cancer,” Dean said. But “it is widely believed that moderate drinking is associated with better heart health and longer life expectancy. And we know that almost half of American women die of heart/vascular causes, whereas about 3 percent die of breast cancer.”
So, for the reader not versed in scientific research, what does this advice mean?
First, when discussing breast cancer risk factors with your doctor, ask them to explain the absolute risk raised by the results of a particular study, compared to the relative risk.
Second, understand that when medical study risks and numbers are reported by journalists, the headlines may reflect relative risk, rather than the news you truly need, which is the absolute risk of a behavior or exposure.
And finally, grab a copy of Cornelia Dean’s book to assist in finding the appropriate context for the reporting of research studies.
