Caffeine intake and salivary concentrations
| Placebo N=24 | Caffeine citrate 5 mg/kg/day N=24 | Caffeine citrate 10 mg/kg/day N=27 | Caffeine citrate 15 mg/kg/day N=27 | Caffeine citrate 20 mg/kg/day N=28 | Any dose of caffeine N=106 | |
| Maternal caffeine intake in preceding 24 hours (mg)* | ||||||
| Baseline | 36.3 (13.9, 83.2) | 63.3 (30.0, 115.6) | 65.2 (10.6, 116.4) | 42.3 (13.9, 67.7) | 41.6 (10.6, 142.0) | 51.5 (16.6, 105.0) |
| Two weeks | 60.5 (10.6, 87.5) | 84.1 (36.3, 110.4); p=0.064 | 39.5 (10.6, 144.8); p=0.675 | 36.3 (7.8, 78.8); p=0.752 | 88.2 (21.2, 175.0); p=0.099 | 63.5 (19.9, 115.6); p=0.252 |
| Term | 77.5 (41.8, 118.4) | 84.6 (60.5, 139.1); p=0.529 | 98.1 (15.5, 121.0); p=0.873 | 60.5 (36.3, 105.0); p=0.396 | 43.2 (10.6, 63.5); p=0.075 | 63.5 (21.2, 112.5); p=0.559 |
| Maternal salivary caffeine concentration at 2 weeks (μg/mL)† | 1.6 (0.5, 2.6) | 1.2 (0.6, 3.1); p=0.919 | 0.2 (0.0, 1.8); p=0.029 | 0.2 (0.0, 2.4); p=0.113 | 1.0 (0.2, 2.9); p=0.523 | 1.1 (0.1, 2.6); p=0.124 |
| Infant salivary caffeine concentration at 2 weeks (μg/mL)‡ | 0.6 (0.3, 0.9) | 17.6 (14.2, 23.8); p<0.001 | 26.1 (11.3, 36.3); p<0.001 | 33.7 (20.2, 51.0); p<0.001 | 71.0 (52.3, 86.5); p<0.001 | 28.3 (18.2, 52.3); p<0.001 |
Data presented are median (IQR).
*Number of mothers with completed surveys at baseline, 2 weeks and term, respectively, are: 23, 22 and 20 in placebo group; 23, 20 and 18 in 5 mg/kg/day group; 23, 22 and 19 in 10 mg/kg/day group; 25, 19 and 18 in 15 mg/kg/day group and 26, 18 and 18 in 20 mg/kg/day group.
†Number of mothers with salivary samples is 19 in placebo group; 16 in 5 mg/kg/day group; 21 in 10 mg/kg/day group; 17 in 15 mg/kg/day group and 14 in 20 mg/kg/day group.
‡Number of infants with salivary samples is 21 in placebo group; 18 in 5 mg/kg/day group; 20 in 10 mg/kg/day group; 18 in 15 mg/kg/day group and 16 in 20 mg/kg/day group.
§P values are from a Wilcoxon rank-sum test, due to highly skewed distributions.