From: Vitamin C and common cold-induced asthma: a systematic review and statistical analysis
Study | Outcome | P (2-tail) for the difference | Estimate of vitamin C effect (95% CI) | Notes |
---|---|---|---|---|
Anah et al. 1980[27] | Incidence of all asthma attacks: | 0.019 | RR = 0.22 (0.06 to 0.81) | All asthma attacks: 9/22 and 35/19 (attacks/persons) in vit C and placebo groups, respectively. See Additional files2 and3 for the calculations. |
 | Incidence of severe and moderate asthma attacks: | 0.003 | RR = 0.11 (0.02 to 0.48) | Severe and moderate asthma attacks: 3/22 and 23/19 (attacks/persons) in vit C and placebo groups, respectively. See Additional files2 and3 for the calculations. |
Proportion of participants who were sensitive to histamine: | 0.0005 | 52 percentage points decrease (25 to 71) | The P-value was calculated from the discordant observations: 12 were sensitive to histamine in the placebo phase but not in the vit C phase; 0 were sensitive to histamine in the vit C phase but not in the placebo phase. See Additional file2 for the calculations. | |
 | Asthma symptom score: | 0.12 | Placebo: 0.72, Vit C: 0.65 | Scale 0 to 3; 0 indicates no symptoms. The P-value was calculated by Schertling et al.[30, 31]. |
 | PEF: | 0.12 | Placebo: 400 L/min, Vit C: 409 L/min | |
Histamine PC20: | 0.0003 | 3.2 fold increase in PC20, (2.0 to 5.1 fold) | Vit C increased histamine PC20 geometric mean from 7.8 to 25.1Â mg/ml. See Additional files2 and3 for the calculations. | |
 | Interaction between the vitamin C effect and the common cold: | 0.003 |  | Interaction test for the vit C effect on PC20 (before/after vit C) and the presence of the common cold (yes/no). See Additional file2 for the calculations. |