CHANGES IN STUDY DESIGN, GENDER ISSUES, AND OTHER CHARACTERISTICS OF CLINICAL RESEARCH PUBLISHED IN 3 MAJOR MEDICAL JOURNALS FROM 1971 TO 1991

OBJECTIVE: To examine trends in study design and other characteristics of original research published in JAMA, Lancet, and the New England J ournal of Medicine (NEJM) between 1971 and 1991. DESIGN: A retrospecti ve cross-sectional study of original clinical research published in JA MA, Lancet, and NEJM during 1971, 1981, and 1991. MEASUREMENTS: Four h undred forty-four articles were independently reviewed by at least two investigators and classified according to study design and other pres elected study characteristics. Changes over time were analyzed by chi- square tests for categorical variables and analysis of variance for co ntinuous variables. MAIN RESULTS: Clinical results doubled, from 17% o f all articles in 1971 to 35% in 1991 (p < 0.004), while case series d ecreased from 30% to 4% (p < 0.0001). Of 118 clinical trials, randomiz ed controlled trials increased from 31% to 76% (p < 0.003) and nonrand omized controlled trials decreased from 42% to 8% (p < 0.002). Multice nter studies increased from 10% to 39% (p < 0.0001) and the prevalence of health services research increased from none in 1971 to 12% in 199 1 (p < 0.001). The proportion of the studies explicitly excluding wome n from the subject population decreased from 11% in 1971 to 3% in 1991 (p < 0.03). In 1991 7% of the studies were composed entirely of men s ubjects, while only 0.7% of the studies were specific to men's health. Twelve percent of the studies in 1991 were specific to women's health . Between 1971 and 1991 there was no change in the prevalence of women first authors or studies addressing women's or minorities' health iss ues. CONCLUSIONS: Several important changes in clinical research studi es published in JAMA, Lancet, and NEJM have taken place between 1971 a nd 1991. Clinical trials have increased in frequency, largely replacin g studies containing ten or fewer subjects. Health services research h as increased in prevalence, reflecting growing interest in studies add ressing the delivery of health care. Our data support the hypothesis t hat exclusion of women from clinical research studies is an important contributor to the paucity of data concerning women's health.