Drs Khalaf et al1 have provided an analysis of regular use of aspirin and risk of pancreatic cancer in the Health Professionals Follow-up Study and the Nurses’ Health Study (NHS), two substantial cohort studies. Given that these 2 studies were recently analyzed by Cao et al2 for the same association, to interpret these reports it would help to clarify some of the data involved in them. In particular, because the 2 analyses seem to cover essentially the same follow-up periods of the 2 cohorts, it is unclear why appreciably different numbers of pancreatic cancer cases were reported.