The search for genetic or blood-based clues that point to a range of diseases has generated much excitement in recent years, but a study out Tuesday says much of that research is exaggerated.
Popular studies that have been widely cited in leading medical journals were among 35 analyzed by John Ioannidis of Stanford University and his colleague Orestis Panagiotou from the University of Ioannina School of Medicine in Greece.
The studies were published between 1991 and 2006 and were later referenced by a minimum of 400 research papers, according to the study published in the June 1 issue of the Journal of the American Medical Association.
But fewer than half showed significant links to disease risks in larger follow-up studies.
And just one in five increased a patient's relative risk by more than 1.37, when one means no risk and two is double the risk. The median relative risk reported by the studies was 2.5.
"We found that a large majority of these highly cited papers suggested substantially stronger effects than that found in the largest study of the same markers and outcomes," said Ioannidis, a prominent analyst of scientific methods.
"Many of these studies were relatively small and among the first to report on the association of interest," he said.
"Discoveries made in small studies are prone to overestimate or underestimate the actual association. Interest in publishing major discoveries leads to selective reporting from chasing significance."
Even scientists are prone to manipulating their figures to show more dramatic results, and often times meta-analyses — or a look at results from multiple independent studies — will over time reveal the true nature of the link, he added.
"We have to learn to trust the bigger picture," said Ioannidis. "And it's better to demand this proof upfront rather than waiting for it to happen on a case-by-case basis," he said.
Copyright AFP
