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April 30, 2001

Study Estimates Gender Bias in U.S. Clinical Trials, Finds Men–Not Women–Underrepresented in Most Research

New Study Compares Male-Only and Female-Only Trials to Mortality Rates

Contrary to longstanding public perception, women do not appear to be under represented or understudied in scientific clinical research trials in the United States, according to a new study by researchers at the Johns Hopkins University Bloomberg School of Public Health. The findings were most pronounced among cancer related clinical trials. The researchers concluded that women are represented in twice as many cancer trials compared to men, even though men die more frequently from the disease and often die at an earlier age. The study is the first to quantify gender bias in clinical research. Researchers measured the levels of bias by comparing male-only and female-only trials with death rates for each sex from heart disease, malignant cancer, and other causes. The findings appear in the April 30, 2001 edition of Statistics in Medicine.

"The findings are important because the perception that females are under represented and their diseases are understudied erodes the public trust, which is essential to continued clinical research," says Curtis L. Meinert, PhD, professor of epidemiology and director of the Center for Clinical Trials at the Johns Hopkins University Bloomberg School of Public Health.

For years, policy makers and the general public have assumed that medical research favored men over women. The perception was so compelling that Congress enacted legislation in 1993 explicitly requiring the inclusion of women in clinical trials.

The researchers contend that any true measure of "fairness" in clinical trials must account for the differences at which death and disease affect men and women. In addition, previous studies conducted by Dr. Meinert and his colleagues already concluded women outnumbered men in clinical trial participation over the last several decades. For the latest study, Dr. Meinert and his colleagues analyzed over 100,000 clinical trials appearing in peer-reviewed scientific journals published in the U.S. between 1965 and 1995. The trials were grouped into male-only and female-only categories, but the vast majority of trials were open to both sexes. Next, the researchers compared the number of single-gender clinical trials to the mortality rates for heart disease and cancer. The investigators also calculated the number of years of potential life lost by participants who died before age 65. Over all, the researchers found no evidence of a pervasive bias against women in clinical trials. According to the researchers, the only consistent bias against women was in heart related clinical trials. Less than one percent of all heart trials were female-only, yet women account for more than a third of heart disease deaths. Investigators also found a bias against men. Males were under represented in most cancer research, even after researchers accounted for specific studies for prostate cancer and breast cancer. Despite the apparent under representation of men in some clinical trials, Dr. Meinert does not believe drastic corrective policies are helpful. He feels to do so would add unnecessary restrictions and expense to medical research.

"Disease is the great equalizer. While the path to disease may be different for men and women, the treatment usually works equally well for both. That does not mean that gender is irrelevant, but that the disease state and history are usually more important. The emphasis should be placed on doing better trials and on better reporting of trials and not on who is being studied," adds Dr. Meinert.

Adele Kaplan Gilpin, PhD, JD, contributed to the research of this study.

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