Media coverage of women's health issues: Is there a bias in the reporting of an association between hormone replacement therapy and breast cancer?

Media coverage of scientific research plays a major role in shaping public opinion and influencing medical practice. When an association is controvers ial, such as with hormone replacement therapy (HRT) and breast cancer, it i s important that a balanced picture of the scientific literature be reporte d. The objective of this study was to assess whether scientific publication s that do and do not support an HRT/breast cancer association were cited in the media in proportions similar to those with which they appear in the sc ientific literature. Scientific publications reporting on the HRT/breast ca ncer association published from January 1, 1995, to June 30, 2000, were ide ntified through a systematic Medline search. Media reports from newspapers, magazines, television, and radio that reported on HRT and breast cancer we re retrieved from an online database. Investigators independently recorded characteristics of the scientific publications and media reports. A total o f 32 scientific publications were identified: 20 (62.5%) concluded there wa s an increased risk of breast cancer associated with HRT (positive publicat ions), and 12 (37.5%) concluded there was no evidence for an association (n ull publications). Nearly half (47%) of the scientific publications were no t cited by the media. There were 203 media citations of scientific publicat ions: 82% were of positive publications and 18% were of null publications, representing a significant excess of citations of positive publications (p < 0.01). Media coverage of this controversial issue is based on a limited s ample of the scientific publications. Moreover, the excess of media citatio ns for positive scientific publications suggests a bias against null scient ific publications.