Fig. 2

Alterations in the gut microbial structure in participants with cognitive impairment. a–c Scatterplots from principal coordinates analysis (PCoA) and permutational multivariate analysis of variance (PERMANOVA), based on Bray–Curtis distances at genus level from the GNHS, the AD case–control study and the CHNS, respectively. In the GNHS, participants were classified into corresponding degrees of cognitive impairment according to their MMSE scores: ‘Mild’ (score ≤ 25); ‘Questionable’ (score 26–29) and ‘Normal’ (score 30). GNHS Guangzhou Nutrition and Health Study, AD Alzheimer’s disease, MCI mild cognitive impairment, NC normal control, CHNS China Health and Nutrition Survey, T tertile