Table 2. Summary of meta-analysis and subgroup analyses on cognition.

Outcome or Subgroup	No. of trials	Participants	Estimated Effect	Test of heterogeneity		P2
				P1	I2 (%)
1.0 Probiotics versus control group	5	297	0.37 (0.14, 0.61)	0.26	24	0.002
1.1 Subgroup by type of disease
1.1.1 AD	3	161	0.36 (0.05, 0.68)	0.12	52.2	0.023
1.1.2 MCI	2	136	0.39 (0.04, 0.73)	0.30	6.4	0.028
1.2 Subgroup by cognitive rating scale
1.2.1 MMSE	3	157	0.57 (0.25, 0.89)	0.44	0	0.001
1.2.2 Non-MMSE	2	140	0.16 (-0.17, 0.50)	0.41	0	0.33
1.3 Subgroup by strains of flora
1.3.1 Multiple	3	161	0.36 (0.05, 0.68)	0.12	52.2	0.023
1.3.2 Sole	2	136	0.39 (0.04, 0.73)	0.30	6.4	0.028

Note: P¹ for heterogeneity: P < 0.1 was considered to indicate significant heterogeneity across studies. I² for heterogeneity: I² > 50% was considered to indicate significant heterogeneity across studies. P² for meta-analysis: P < 0.05 was considered to indicate a significant effect of probiotics on cognition by using a fixed-effects model.