Evaluating the real-world representativeness of participants with mild cognitive impairment in Canadian research protocols: a comparison of the characteristics of a memory clinic patients and research samples

Abstract

Background Studies of mild cognitive impairment (MCI) employ rigor­ous eligibility criteria, resulting in sampling that may not be representative of the broader clinical population. Objective To compare the characteristics of MCI patients in a Calgary memory clinic to those of MCI participants in published Canadian studies. Methods Clinic participants included 555 MCI patients from the PROspective Registry of Persons with Memory SyMPToms (PROMPT) registry in Calgary. Research participants in­cluded 4,981 individuals with MCI pooled from a systematic literature review of 112 original, English-language peer-reviewed Canadian studies. Both samples were compared on baseline sociodemographic variables, medical and psychiatric comorbidities, and cognitive performance for MCI due to Alzheimer’s disease and Parkinson’s disease. Results Overall, clinic patients tended to be younger, more often male, and more educated than research participants. Psychiatric dis­orders, traumatic brain injury, and sensory impairment were commonplace in PROMPT (up to 83% affected) but > 80% studies in the systematic review excluded these conditions. PROMPT patients also performed worse on global cognition measures than did research participants. Conclusion Stringent eligibility criteria in Canadian research studies ex­cluded a considerable subset of MCI patients with comorbid medical or psychiatric conditions. This exclusion may con­tribute to differences in cognitive performance and outcomes compared to real-world clinical samples.