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To the Editor: In a randomized clinical trial assessing the effects of a 24-week physical activity intervention on cognition, Dr Lautenschlager and colleagues¹ reported a significant difference in performance on their primary outcome measure. However, the numbers in the published tables are inconsistent, raising concerns that the reported significant finding may be attributable to baseline differences in the initial cognitive state of the 2 groups.

Table 1 lists the baseline characteristics of the 85 trial participants in the exercise and control groups. Means for scores on the Alzheimer Disease Assessment Scale–Cognitive Subscale (ADAS-Cog), the primary outcome measure, are both 7.0. However, in Table 7, when the control group is divided between those who completed the study and those who dropped out, the mean baseline ADAS-Cog score in the same 85-person control group is 8.1. Given the higher frequency of persons with amnestic mild cognitive impairment in the control group, a . . . [Full Text of this Article]

James A. Mortimer, PhD
jmortime@health.usf.edu
Department of Epidemiology and Biostatistics
University of South Florida
Tampa

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