A Literature Review of Methodologies Used in Randomized Clinical Trials of Agitation in Alzheimer's Disease

Agitation is a common and burdensome symptom associated with Alzheimer's disease (AD). This is a narrative literature review of the designs and methods used in randomized clinical trials of agitation in patients with AD; sources range from published, to completed but not published, to ongoing studies in the past 10 years. Selection for review included blinded, randomized trials conducted to assess the effect of a pharmacological intervention for which agitation in patients with AD was among the prespecified end points. Key criteria for exclusion included open-label studies, trials of dementia not specific to AD, or mixed populations of AD and unspecified dementia. A search of PubMed and clinicaltrials.gov databases identified 36 trials for which agitation was among the prespecified end points: 18 were published trials and 18 were completed but not published or ongoing. There was significant heterogeneity among AD studies in terms of diagnostic criteria, assessment of severity of disease and agitation, sample size and powering assumptions, treatment duration, patient age and cognitive status, and outcomes measurements. Few studies used a mitigation strategy for placebo response. Accumulating evidence suggests that it is important to consider the following in trial design: thresholds for baseline severity of agitation and AD; use of prespecified accepted criteria to define agitation; and use of standardized, validated tools to measure treatment effects during a trial. Adoption of these design strategies might help improve signal detection and bring us closer to identifying the most appropriate, effective, and safe treatments for agitation in patients with AD.