With concern, we read the trials conducted by Sato and colleagues comparing risedronate sodium with placebo in male patients with stroke1 and female patients with Alzheimer disease (AD).2
Both trials were conducted in a single center. Yet, patients (500 women with AD and 280 men with stroke) were recruited in only 3 months: the patients with AD in March and April 2003 and the patients with stroke in April and May 2003. Related to a third single-center trial with risedronate in 374 female patients with stroke at the same hospital that was published by the group in 2005,3 a correspondence letter4 expressed concern about the high frequency of recruitment, which was performed in only 4 months (between April and July 2003).3 In their reply, Sato and colleagues5 stated that their hospital is a specialized center for stroke and that they treat about 2800 patients with stroke per year. Even if these circumstances are taken into account, recruiting 280 male patients with stroke who meet all eligibility criteria in a single center in only 2 months appears implausible. This applies to an even greater extent to the 500 female patients with AD. Of note, Sato et al1,2 stated that only 1 physician (ie, Sato himself) did all AD diagnoses as well as the follow-up assessments of all 780 patients every 4 weeks.
Halbekath JM, Schenk S, von Maxen A, Meyer G, Mühlhauser I. Risedronate for the Prevention of Hip Fractures: Concern About Validity of Trials. Arch Intern Med. 2007;167(5):513-515. doi:10.1001/archinte.167.5.513-b