Here we go again. Headlines across America blaring lines like, “Coffee may reduce stroke risk.”
It was a big study, but an observational study. Not a trial. Not an experiment. And, as we say so many times on this website that you could almost join along with the chorus, observational studies have inherent limitations that should always be mentioned in stories. They can’t prove cause and effect. They can show a strong statistical association, but they can’t prove cause and effect. So you can’t prove benefit or risk reduction. And stories should say that.
“The problem with this type of study is that there are too many factors unaccounted for and association does not prove causality, said Dr. Larry B. Goldstein, director of the Duke Stroke Center at Duke University Medical Center.
“Subjects were asked about their past coffee consumption in a questionnaire and then followed over time. There is no way to know if they changed their behavior,” Goldstein said.
And, he noted, there was no control for medication use or other potential but unmeasured factors.
“The study is restricted to a Scandinavian population, and it is not clear, even if there is a relationship, that it would be present in more diverse populations. I think that it can be concluded, at least in this population, that there was not an increased risk of stroke among coffee drinkers,” he said.”
When you don’t explain the limitations of observational studies — and/or when you imply that cause and effect has been established — you lose credibility with some readers. And you should. Read more »
Cancer of the ovary is a particularly nasty disease. It often remains asymptomatic until it has reached an advanced, incurable stage, and scientists have been unable to develop an effective screening test for the disease like the ones in widespread use for cancers of the breast and cervix.
The dismal status of ovarian cancer screening was underscored a year ago when an NIH-sponsored study showed that over 70 percent of cancers detected by transvaginal ultrasound and CA 125 biomarker testing — the two best ovarian screening tests we’ve got — had reached stage III or IV at the time the patients screened positive. That’s about what happens when women aren’t screened at all.
That wasn’t the worst of it, however. In just the first year of that screening program, positive test results obligated 566 surgical procedures which uncovered only 18 cancers. That’s an awful lot of unnecessary surgery and associated morbidity right there. Things were no better on the false-negative side of things. Overall, 89 cases of ovarian cancer were diagnosed during the NIH study, and a third of them had been missed by both screening modalities.
The NIH study didn’t evaluate the impact of screening on ovarian cancer mortality, but a recent study by Laura Havrilesky and colleagues at Duke did indeed address the point. Sadly, the results were abysmal. Read more »
*This blog post was originally published at Pizaazz*
Four-year-old Devan Tatlow’s struggle with leukemia has caused quite a stir on the Internet, prompting celebs like Paris Hilton and Kim Kardashian to encourage people to donate their bone marrow. Dr. Jon LaPook talks with Devan’s family about their search for a match.
Imagine throwing a lifesaving treatment in the garbage. That’s exactly what happens in the United States over ten thousand times a day because we do not routinely offer to collect precious umbilical cord blood at the time of birth. Thousands of Americans — many of them children — needlessly die annually because they cannot find either a bone marrow or umbilical cord blood match to help treat conditions like lymphoma and leukemia. Yet umbilical blood is discarded as medical waste in the vast majority of the more than four million births occurring each year. Read more »
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