Don't believe everything medical studies tell you
By Lindsey Tanner

July 13, 2005

CHICAGO - Here's some medical news you can trust: A new study
confirms that what doctors once said was good for you often
turns out to be bad - or at least not as great as initially
thought.

The report is a review of major studies published in three
influential medical journals between 1990 and 2003, including
45 highly publicized studies that initially claimed a drug or
other treatment worked.

Subsequent research contradicted results of seven studies - 16
percent - and reported weaker results for seven others, an
additional 16 percent. That means nearly one-third of the original
results didn't hold up, according to the study in today's Journal of
the American Medical Association.

"Contradicted and potentially exaggerated findings are not uncommon
in the most visible and most influential original clinical
research," said study author John Ioannidis, a researcher at the
University of Ioannina in Greece.

Experts say the study is a reminder to doctors and patients that
they shouldn't put too much stock in a single study and understand
that treatments often become obsolete with medical advances.

"A single study is not the final word, and that is an important
message," editors at the New England Journal of Medicine  said in a
statement about the study.

The discredited studies dealt with a wide range of drugs and
treatments. Hormone pills were once thought to protect menopausal
women from heart disease but later were shown to do the opposite.

Contrary to initial results, vitamin-E pills haven't been shown to
prevent heart attacks.

Contradictions also included a study that found nitric oxide doesn't
improve survival in patients with respiratory failure, despite
earlier claims. And a study suggested that an antibody treatment
didn't improve survival in certain sepsis patients; a smaller
previous study found the opposite.

Ioannidis acknowledged an important but not very reassuring caveat,
"There's no proof that the subsequent studies . . . were necessarily
correct." But he noted that in all 14 cases in which results were
contradicted or softened, the subsequent studies were either larger
or better designed. Also, none of the contradicted treatments is
currently recommended by medical guidelines.

Ioannidis' study examined research in JAMA, The New England Journal
of Medicine and the British medical journal The Lancet - prominent
publications whose weekly studies help feed a growing public
appetite for medical news.

Not by accident, this week's JAMA  also includes a study
contradicting previous thinking that stomach-lying helped improve
breathing in children hospitalized with acute lung injuries. The new
study found they did no better than patients lying on their backs.

Dr. Catherine DeAngelis, JAMA's  editor, said she included the study
with Ioannidis' report to highlight the nature of medical research.

"The crazy part about science and yet the exciting part about
science is you almost never have something that's black-and-white,"
she said.

Ioannidis said scientists and editors should avoid "giving selective
attention only to the most promising or exciting results" and should
make the public more aware of the limitations of science.

"The general public should not panic" about discredited studies, he
said. "We all need to start thinking more critically."

DeAngelis also noted that the media can complicate matters with
misleading or exaggerated headlines about studies.

Ioannidis said the studies most likely to be contradicted later were
what scientists call "nonrandomized" studies. Those are often based
on observations of patients' lifestyles rather than on results from
a drug or other intervention assigned by researchers.

... Conserve air -- breathe less.