The use of the mini-mental state examination in recruitment for substance abuse research studies.

BACKGROUND: Substance abuse is associated with cognitive impairment. Participation in clinical addiction research can be cognitively demanding. Screening tools can identify cognitively impaired subjects. We examined the use of the mini-mental state examination (MMSE) as an entry criterion in three randomized controlled substance abuse clinical trials.
METHODS: In each of the three studies, we calculated the proportion of subjects excluded due to MMSE scores (<21) suggestive of cognitive impairment. We estimated the potential impact on enrollment based on the number of excluded subjects. Separately, for two of the studies, we assessed the impact of cognitive function on participation in follow-up using multivariable logistic regression.
RESULTS: Of all persons screened for enrollment, 1.6% (171/10,791) were ineligible based solely on a MMSE score of <21. We estimate that 119 of these 171 ineligible persons would have consented and enrolled. These 119 persons would have represented 9.3% of all enrolled subjects across these studies. For subjects in a study in an inpatient detoxification unit, a higher MMSE score was associated with higher odds (adjusted odds ratio 1.15, 95% CI 1.03-1.30) of completing at least one follow-up assessment. A similar impact on subject follow-up was not observed in a study of medical inpatients with unhealthy alcohol use (adjusted odds ratio 1.01, 95% CI 0.86-1.20).
CONCLUSION: Screening for cognitive impairment using the MMSE excludes a small, but substantial, number of persons from addiction research studies. Cognitive ability, as captured by the MMSE may impact follow-up. These data support cognitive screening of substance abuse research subjects.