Gender indexing in publications of clinical trials: 1991-2008.

Background: In 1993 Congress passed the NIH Revitalization Act, which instructed the Director of the NIH to ensure that phase III clinical trials are 'designed and carried out in a manner sufficient to provide for a valid analysis of whether the variables being studied in the trial affect females or members of minority groups, as the case may be, differently than other subjects in the trial.'

Purpose: The purpose of this article is to track the PubMed indexing of gender in clinical trial publications since 1991 with a view toward assessing the impact of the legislation on the number of gender specific trials.

Methods: We searched PubMed for full-length publications from years 1991 to 2008 of research on humans indexed as publication type 'clinical trial', 'randomized clinical trial' and multicenter randomized trial ('multicenter study' AND 'randomized clinical trial'), and counted the number of trials indexed as male-only, female-only, male and female, and gender unknown in PubMed.

Results: The majority of trial publications were indexed in PubMed as including both genders. The proportion of publications indexed as including both genders has increased while the number of publications not indexed with respect to gender and the number of publications indexed as male-only have decreased. In 2005, approximately 13% of NIH expenditures were for female specific or related research compared to 6% for male specific or related research.

Limitations: The proportion of clinical trial publications that were indexed in PubMed as including females began to increase before the legislation so it is difficult to conclude that changes in the number of female-only or male-only trials are due to the legislation. PubMed listings do not include gender enrollment, so female and male enrollment totals could not be compared.

Conclusions: The NIH policy should be rewritten to be made gender neutral to bring it in line with the principle of justice as embodied in the Belmont Report.