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Table 2 Subgroup analyses for the effect of probiotic dairy products on respiratory tract infections

From: Effect of probiotic fermented dairy products on incidence of respiratory tract infections: a systematic review and meta-analysis of randomized clinical trials

Subgrouped by No. of data sets RRa (95 % CI) P valueb I2 (%)c P valued
Overall 33 0.81 (0.74 to 0.89 ) ˂0.001 54.8 ˂0.001
Population type
 Children 17 0.82 (0.73 to 0.93 ) 0.001 47.4 0.01
 adults 8 0.81 (0.66 to 1.00 ) 0.04 41.8 0.07
 Elderly 8 0.78 (0.61 to 0.98 ) 0.03 34.2 0.15
Probiotic genus
 Lactobacillus 31 0.81 (0.74 to 0.90 ) ˂0.001 55.6 ˂0.001
 Bifidobacterium 2 0.90 (0.41 to 2.01 ) 0.80 64.6 0.09
Dairy type
 Milk 21 0.83 (0.74 to 0.92 ) ˂0.001 58.0 ˂0.001
 Dairy drink 7 0.80 (0.64 to 1.02 ) 0.07 54.3 0.04
 Yoghurt 5 0.71 (0.44 to 1.13 ) 0.15 49.6 0.09
Type of infection      
 RTIs 6 0.82 (0.67 to 1.00 ) 0.05 71.1 0.004
 URTIs `17 0.83 (0.73 to 0.93 ) 0.002 52.3 0.006
 LRTIs 10 0.78 (0.60 to 1.01 ) 0.06 43.3 0.07
  1. RTIs Respiratory tract infections, URTIs Upper respiratory tract infections, LRTIs Lower respiratory tract infections, RR relative risk
  2. aEffect size was expressed as relative risk and 95% confidence interval
  3. bFor meta-analysis: P ≤ 0.05 was considered to be a significant effect by using a random-effects model
  4. cThe I2 statistic was calculated by using Cochran’s test, and I2  statistic > 50% was considered to indicate significant heterogeneity across studies
  5. dP value for I2