MAPT and early-onset autosomal dominant Alzheimer disease: Nevertheless, based on the qualitative synthesis of the 27 included studies, MBI was frequently linked to Alzheimer's disease (AD) abnormalities - both in biomarkers and brain imaging studies.<h4>Conclusions</h4>Across studies, MBI appears to be linked to specific neurobiological markers of AD, including Aβ and tau brain deposition, as well as alterations in the mesolimbic pathway and neurodegenerative and neuroinflammatory fluid biomarker levels.