Daily Bowel Movements are Associated with Stronger Gut-Brain Phase-Amplitude Coupling and Better Cognitive Performance

Key results

1. SuggestedWomen with daily bowel movements had a better CANTAB-based global cognitive composite than women with less-frequent bowel movements. The difference held after socioeconomic adjustment, but no individual cognitive test differed between the groups.

   CANTAB composite z (higher = worse) was lower in the daily group (CI [0.05 0.63], p = 0.02; 38 vs 38 women, 2 excluded from cognitive analyses). It stayed lower after socioeconomic adjustment (β = 0.30, CI [0.03 0.57], p = 0.03). Across participants, weekly bowel movements vs composite: Spearman r = -0.29, p = 0.02. · Women with daily bowel movements show better…; Exploring links between gut- and brain…; Cognitive Tests

2. SuggestedPhase-amplitude coupling between the gastric rhythm and EEG alpha amplitude over a parieto-frontal electrode cluster was stronger in the daily bowel movement group and rose with weekly bowel movement count. Gastric and alpha peak frequencies did not differ between groups.

   Modulation Index (MI) over the region of interest (ROI) found by cluster-based permutation against cross-person surrogates: daily vs less-frequent group r = 0.26, p = 0.03; Spearman bowel movements vs ROI MI r = 0.29, p = 0.01. Between groups, EEG alpha peak frequency p = 0.33 and EGG peak frequency p = 0.93. Coupling was weaker in the Go-No-Go task than at rest (p < 0.005). · Women with daily bowel movements show better…; Exploring links between gut- and brain…; Groups with different BM frequency show similar…; Significance Analysis of Phase Amplitude…

3. ShownAcross two baseline visits in the less-frequent group, the gastric-alpha MI had moderate test-retest reliability, lower than that of EEG alpha power. The same peak EGG electrode was selected at both visits for 51.6% of participants.

   In 31 women (V1 vs V3), intraclass correlation: MI ICC(3,1) = 0.50, 95% CI [0.18, 0.72]; alpha power ICC(3,1) = 0.89 [0.78, 0.94]; peak gastric frequency ICC(3,1) = 0.55 [0.25, 0.76]. The selected EGG electrode agreed exactly in 51.6% of participants. MI tended to be higher at the retest visit (p = 0.05). · Moderate test re-test reliability for modulation…; MI Test-retest reliability; Methods Participants

4. SuggestedFaecal acetate, propionate and butyrate, quantified by 1H-NMR, were lower in the less-frequent bowel movement group, and all three were positively associated with gut-brain MI.

   Group differences (Table 3) are reported as significantly lower in the less-frequent group; Spearman correlations with ROI MI (Table 4) are described as positive associations for all three SCFAs, and Benjamini-Hochberg FDR control was applied to both SCFA analyses. The concentrations, coefficients and p-values are not given in the text. One outlier sample was excluded after its NMR spectrum was reviewed. · Women with daily bowel movements show better…; Exploring links between gut- and brain…; Correlation Analyses; Outlier Handling and Missing Data Imputation

5. SuggestedIn a path model, bowel movement frequency predicted total faecal SCFA, which in turn predicted MI. Neither SCFA nor MI predicted cognition, while bowel movements kept a direct association with the cognitive composite.

   lavaan path analysis, 5000 bootstrap iterations: bowel movements to total SCFA β = 0.26, z = 2.86, p < 0.005; SCFA to MI β = 0.35, z = 3.31, p < 0.005; direct bowel movements to cognition β = -0.25, z = -2.35, p = 0.02; SCFA to cognition β = -0.07, p = 0.55; MI to cognition β = 0.02, p = 0.89; bowel movements to MI β = 0.16, p = 0.09. · Association between Bowel Movements and…; Mediation Analyses