Preserving cognition, quality of life, physical health and functional ability in Alzheimer's disease: the effect of physical exercise (ADEX trial): rationale and design.

BACKGROUND Exercise is hypothesized to improve cognition, physical performance, functional ability and quality of life, but evidence is scarce. Previous studies were of short duration, often underpowered and involving home-based light exercise programs in patients with undefined dementia. The aim of the ADEX ('Preserving Cognition, Quality of Life, Physical Health and Functional Ability in Alzheimer's Disease: the Effect of Physical Exercise') trial is to establish whether aerobic exercise is effective in improving cognition as well as in reducing the prevalence of psychiatric symptoms among patients with Alzheimer's disease (AD). METHODS The ADEX study is a multicenter, single-blind, randomized trial with two arms: an intervention group attending 16 weeks of continuously supervised moderate-to-high intensity aerobic exercise and a control group receiving usual care. We plan to recruit 192 patients with mild AD. The primary outcome measure is change from baseline in cognitive performance at 16 weeks (as measured by the Symbol Digit Modalities test). CONCLUSIONS To our knowledge this is the first large-scale controlled study to investigate the effects of supervised moderate aerobic exercise on cognition in patients with AD. Recruitment began in January 2012 and results are expected to be available in 2014. We summarize the methodological challenges we and other studies have faced in this type of complex multicenter intervention with unique challenges to study design.