In this issue of the ARCHIVES, Chan et al1 report a strong association between aspirin use and reduced cardiovascular mortality in middle-aged and older women. This analysis of almost 80 000 women is derived from the Nurses' Health Study (NHS), a well-known and well-conducted observational research effort that has been ongoing for about 30 years. Readers may recall another study on a similar topic published in 2005, the Women's Health Study (WHS).2 That trial, carried out during more than 11 years in almost 40 000 women, reported that aspirin therapy had no effect on cardiovascular or other mortality. Which of these mega-studies is right? Both somehow? Neither?
Baron JA. Can Aspirin Keep Mortality at Bay?. Arch Intern Med. 2007;167(6):535-536. doi:10.1001/archinte.167.6.535