Article

Knowledge of treatment assignment and failing to analyze results by
randomized treatment groups--an intention-to-treat analysis--may cause bias in
the treatment effect estimate in randomized controlled trials. This study was
undertaken to determine the difference in lower limb muscle strength measured by
blinded vs. by unblinded outcome assessors in 73 progressive resistance strength
training trials conducted in older adults. DESIGN: Retrospective analysis of
randomized controlled trials published before 2007. RESULTS: Meta-regression
analyses showed that trials that used blinded assessors (n = 18) tend to report
smaller effect sizes than do those that used unblinded assessors (n = 55), with a
difference of -0.80 (95% confidence interval, -1.35 to -0.25). This result still
holds even after adjusting for the use of an intention-to-treat analysis, with an
adjusted difference of -0.65 (95% confidence interval, -1.26 to -0.04). The
reported effects were exaggerated in trials that used unblinded assessors.
CONCLUSIONS: This study suggests that assessor blinding is important and is a
safeguard to the internal validity of exercise trials in older adults.

Langue : ANGLAIS