Table 4.
Multivariable analysis of urinary caffeine and caffeine metabolites and bronchodilator response.
| Model 1 |
Model 2 |
|
|---|---|---|
| Bronchodilator response (%) | β, (95% confidence interval), P-value | |
| Participants without current asthma (n = 155) | ||
| Caffeine | −0.49 (−2.76 to 1.78), 0.66 | −1.16 (−3.09, 0.77), 0.23 |
| Paraxanthine | −0.43 (−3.23, 2.37), 0.76 | −1.08 (−2.53, 1.38), 0.38 |
| Theobromine | 0.12 (−1.82, 2.05), 0.90 | −0.60 (−2.66, 1.46), 0.56 |
| Theophylline | −0.78 (−3.63, 2.07), 0.58 | −1.70 (−4.11, 0.72), 0.16 |
| Participants with current asthma (n = 23) | ||
| Caffeine | 5.16 (1.36, 8.95), <0.01 | 2.32 (−0.48, 5.12), 0.10 |
| Paraxanthine | 5.38 (1.28, 9.48), 0.01 | 2.71 (−0.08, 5.49), 0.06 |
| Theobromine | 3.41 (−0.71, 7.54), 0.10 | 2.45 (−0.73, 5.64), 0.13 |
| Theophylline | 6.98 (2.28, 11.69), <0.01 | 3.32 (−0.18, 6.82), 0.06 |
Urinary levels of caffeine or its metabolites were first divided by the urinary creatinine level and then log10-transformed.
All models adjusted for age, sex, race and ethnicity, annual household income, body mass index, serum cotinine, pack-years of cigarette smoking, use of oral or inhaled steroids in the past 2 days, and time of the day when the samples were collected. Model 2 was additionally adjusted for pre-bronchodilator FEV1.