Table 4 Difference between the mean number of RTI episodes per year during the follow-up period and the number of episodes of RTI before inclusion in the study stratified according to the presence of concomitant respiratory diseases in the treated (specific extract of duck liver and heart) and untreated groups

COPD^a

 - No

-4.19 ± 1.60

-4.85 ± 1.49

-3.40 ± 1.36

p < 0.001

 - Yes

-3.66 ± 1.00

-4.16 ± 0.93

-3.11 ± 0.77

p = 0.033

p = 0.330

p = 0.152

p = 0.949

Respiratory allergy:

 - No

-4.10 ± 1.63

-4.75 ± 1.63

-3.38 ± 1.29

p = 0.003

 - Yes

-4.13 ± 1.43

-4.76 ± 1.19

-3.33 ± 1.31

p < 0.001

p = 0.187

p = 0.860

p = 0.051

Asthma:

 - No

-4.15 ± 1.60

-4.84 ± 1.56

-3.32 ± 1.22

p < 0.001

 - Yes

-4.00 ± 1.33

-4.47 ± 0.92

-3.84 ± 1.52

p = 0.013

p = 0.909

p = 0.182

p = 0.154

Other respiratory diseases:

 - No

-4.07 ± 1.45

-4.73 ± 1.26

-3.36 ± 1.30

p < 0.001

 - Yes

-4.77 ± 2.52

-4.98 ± 2.57

-2.96 ± 0.86

p = 0.015

p = 0.394

p = 0.980

p = 0.360