Study Finds Women Not Under-represented in U.S. Clinical Trials

Although it's been a longstanding perception that, compared to men, women and their health conditions have been understudied in U.S. scientific clinical trials, researchers at the Johns Hopkins School of Public Health, who scrutinized more than 100,000 trials reported in U.S. journals between 1966 and 1998, have found no evidence of gender bias. Their report appears in the October 2000 issue of Controlled Clinical Trials.

"The prevailing view has been that the nation's clinical research enterprise has been tilted in favor of men, and especially so in regard to clinical trials," said lead author Curtis L. Meinert, PhD, professor, Epidemiology, and director of the Center for Clinical Trials at the Johns Hopkins School of Public Health. "Therefore, we were interested in examining the extent to which this perception had a basis in fact, as seen by the gender-mix represented in published trials. We didn't find evidence of any systematic bias against women."

Complaints of a historical lack of research focusing on women's health concerns have been voiced at least since the 1980s, and led to a 1990 National Institutes of Health directive underscoring the importance of including female participants in clinical trials. By 1993, the perception of medical research favoring men's health conditions caused the 103rd Congress to enact legislation explicitly requiring the inclusion of women in clinical trials.

To obtain counts of the numbers of males and females in U.S. trials, the authors of the present study classified by gender more than 100,000 clinical trials published between 1966 and 1998 in U.S. journals. The authors found that 55 percent of the studies they scrutinized involved both men and women, 12 percent involved men only, 11 percent involved women only, and 21 percent of studies did not specify gender.

Even the majority (64 percent) of trials investigating heart disease -- a disease traditionally considered to affect men disproportionately -- involved both men and women, although many more of the single-gender trials were male-only (14 percent) than female-only (0.1 percent). In the case of cancer trials, there were 2.5 times as many female-only trials as male-only trials.

In 1998, the latest year considered by the investigators, 65 percent of that year's 8,903 trials involved males and females, 10 percent involved men only, 11 percent involved women only, and the remainder, 14 percent, could not be classified as to gender-mix.

In addition, the authors retrieved and read 724 trials that appeared between 1966 and 1998 in five widely circulated medical journals (the Annals of Internal Medicine, British Medical Journal, Journal of the American Medical Association, The Lancet, and The New England Journal of Medicine). Of 603 trials providing gender breakdowns, 60 percent involved both men and women, 11 percent were male-only, and 13 percent were female-only.

"Overall," said Meinert, "we find little to support the perception that women have been under-represented or understudied in trials, or that there is an effort bias in favor of men. The counts, even in the decade preceding the one in which Congress acted, are not suggestive of systematic understudying of women in trials."