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Selection bias

A study led by a School of Public Health researcher examines the effect of selection bias in cohort studies, following the same group of people over many years. The paper was published online Oct. 19 in the journal Epidemiology. Selection bias can occur when a non-random subgroup drops out of the study.

The article cites heavy alcohol users, who may be more likely to drop out of a standard cohort study, as an example of selection bias. Since heavy alcohol users have a higher rate of mortality, this selection bias would skew the results.

The study found that targeted learning and weighting — a statistical technique in which a certain data item is emphasized more than others — can address issues of selection bias.

The paper’s coauthors include Chanelle Howe, assistant professor of epidemiology; Stephen Cole, professor of epidemiology at the University of North Carolina Gillings School of Global Public Health; Bryan Lau, associate professor of epidemiology at Johns Hopkins Bloomberg School of Public Health; and Joseph Eron Jr., professor of medicine at UNC School of Medicine.

Preventing hemorrhages

Researchers led by Assistant Professor of Neurology Shadi Yaghi found no effective treatments for symptomatic intracerebral hemorrhages, which entail massive bleeding inside the head, according to a University press release. The paper was published online Monday in the Journal of the American Medical Association Neurology.

This type of hemorrhage occurs in 6 percent of patients treated with a specific protein for ischemic stroke, which is a life-threatening condition that occurs when blood is blocked from reaching the brain, according to the study. The lack of effective treatments can be attributed to delays in diagnosing and treating the hemorrhage.

“This study included 128 patients and showed that the treatments used were not effective in improving the mortality related to this condition,” Yaghi said in the press release.

Treatments that were tested included surgery, vitamin K, fresh frozen plasma and various hemostatic agents that promote blood clotting, according to the study.

Out of these treatments, only surgery resulted in a small but statistically non-significant improvement in outcome.

Amphibian ability

The ancestors of salamanders and other amphibians once had the capacity to regrow limbs and organs, according to a study involving a University researcher and published online Monday in the journal Nature.

Researchers examined the limbs of amphibians in 290 million-year-old fossils in comparison to the limbs of modern salamanders, which retain the ability to regrow body parts, according to a University press release.

The findings suggest that ancient amphibians had the same ability but lost it in the intervening evolutionary history, according to the press release.

“The amphibians fossilized under excellent conditions for preservation and are represented by a large number of individuals and developmental stages,” Florian Witzmann, a visiting scientist in the Department of Ecology and Evolutionary Biology, said in the press release. “This extraordinary fossil record allowed for the detailed study of limb development and regeneration.”


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