Bilingualism associated with different gray matter patterns in Alzheimer's variants but comparable cognition

This observational study compared gray matter volume (GMV) and cognitive performance between bilingual and monolingual individuals with two Alzheimer's disease variants: amnestic AD (n=136) and logopenic variant primary progressive aphasia (lvPPA, n=88). The total sample included 224 participants with neuropsychological assessments and structural MRI. The exposure was bilingualism, with monolingualism serving as the comparator.

In amnestic AD, bilinguals exhibited less GMV in hippocampal, fusiform, and occipital regions compared to monolinguals. In lvPPA, bilinguals had less temporal and occipital volumes but greater volumes in inferior parietal regions. Despite these structural differences, cognitive performance between monolinguals and bilinguals was comparable within each disease variant. Effect sizes, absolute numbers, and p-values were not reported for these findings.

Safety and tolerability data were not reported. Key limitations of the study were not specified, but the observational design precludes causal inference. The practice relevance was not reported, and funding/conflicts were not disclosed. This study adds to mixed evidence regarding bilingualism's association with brain structure in neurodegenerative conditions, with scarce research across specific AD variants.