Overall, the strength of the present study is that it allows for the possibility of addressing the impact of habitual caffeine consumption in a cohort including only MCI and AD patients very well described at the clinical, neuropsychological, MRI, and CSF biomarker levels, as well as for the possibility of adjusting statistical analyses of known confounding factors for AD (APOE ε4, age, sex, education level) and caffeine intake (smoking). Here, APOE is linked to Alzheimer disease.