Table 1.
Subject characteristics
| Val/Val | Val/Met | P-value | |
|---|---|---|---|
| Sex (female / male) | 4 / 7 | 4 / 7 | n/a |
| Age (years) | 23.7 ± 0.6 | 24.0 ± 0.8 | 0.3 |
| Alcohol consumption (drinks/week) | 2.9 ± 0.6 | 2.9 ± 0.9 | 0.9 |
| Caffeine consumption (mg/day) | 124.1 ± 27.1 | 116.4 ± 30.2 | 0.8 |
| Body mass index (kg/m2) | 21.6 ± 0.4 | 22.2 ± 0.4 | 0.3 |
| Trait anxiety | 38.7 ± 2.2 | 36.8 ± 2.4 | 0.4 |
| Diurnal preference | 2.9 ± 0.3 | 3.2 ± 0.1 | 0.3 |
| Daytime sleepiness | 6.6 ± 0.5 | 7.5 ± 0.6 | 0.3 |
Values represent means ± SEM (n = 11 per group). Caffeine consumption was estimated based on the following average caffeine contents per serving: Coffee: 100 mg; Ceylon or green tea: 30 mg; Cola drink: 40 mg (2 dL); Energy drink: 80 mg (2 dL); Chocolate: 50 mg (100 g). Trait anxiety,16 diurnal preference,50 and daytime sleepiness51 values were based on validated questionnaires. P-values refer to 2-tailed, paired t-tests.