Reasons Alzheimer’s Patients are Omitted from Clinical Trials

A study in the British Journal of Clinical Pharmacology assessed the reasons that prevent Alzheimer’s disease (AD) patients from being included in clinical trials. It is interesting that no study has evaluated the main medical and non-medical factors that explain the non-inclusion in studies.

While reviewing the database of a dementia clinic for involving patients in a clinical trial, the authors decided to review the reasons for exclusion from research studies. Of 205 AD patients who were not selected, the reasons for non-inclusion were:

  • Abnormalities on MRI (56.9%, 88.9% of which were white matter lesions)
  • Unauthorized medication (37.3%)
  • The lack of a study partner/informant (37.1%)
  • The presence of a non-authorized disease (24.4%)
  • Contraindication to MRI (9%)
  • A change in diagnosis over time (3.9%)
  • Visual/auditory impairments (2.9%)
  • Alcohol abuse (2%)
  • An insufficient educational level (1%).

The researchers also noted that AD patients who were included in randomized double-blind controlled trials (RCTs) are younger that average (with mean age 65.5 years). This is probably because they have fewer comorbid conditions and fewer associated treatments and are more likely to have a study partner, when compared with older AD patients. In contrast, individual refusals to participate in a RCT do not appear to be a real barrier for overall trial accrual. They found that 28.3% of the patients  agreed to participate and 4.9% declined.