Table 3.
Polysomnography Results
| Variable | Unadjusted Results |
Adjusted for Covariates* |
||||
|---|---|---|---|---|---|---|
| Caffeine Mean (SD), Median (IQR), or n (%) (n = 97) | Placebo Mean (SD), Median (IQR), or n (%) (n = 100) | Mean Difference†, Rate Ratio‡, or Odds Ratio§ (95% CI) | P Value | Mean Difference†, Rate Ratio‡, or Odds Ratio§ (95% CI) | P Value | |
| Primary outcome | ||||||
| Obstructive apnea–hypopnea index, n/h | 0.3 (0.1 to 0.6) | 0.3 (0.1 to 0.8) | 0.95‡ (0.58 to 1.53) | 0.82 | 0.89‡ (0.55 to 1.43) | 0.63 |
| Secondary outcomes | ||||||
| Sleep architecture | ||||||
| Lights off (evening; clock time)|| | 21:23 (51) | 21:27 (62) | −4† (−21 to 12) | 0.60 | −4† (−19 to 10) | 0.59 |
| Lights on (morning; clock time)|| | 7:24 (44) | 7:09 (51) | 15† (1 to 28) | 0.034 | 12† (−1 to 26) | 0.077 |
| Total recording time, min¶ | 600.7 (52.7) | 579.6 (66.9) | 21.1† (3.9 to 38.3) | 0.017 | 19.2† (3.3 to 35.2) | 0.019 |
| TST, min¶ | 551.0 (52.7) | 531.9 (63.5) | 19.2† (2.5 to 35.8) | 0.024 | 18.3† (3.0 to 33.5) | 0.020 |
| Sleep efficiency, %¶ | 91.8 (4.9) | 91.8 (4.4) | −0.1† (−1.4 to 1.3) | 0.94 | 0.1† (−1.3 to 1.4) | 0.91 |
| Sleep latency, min¶ | 16.2 (18.6) | 17.7 (18.4) | −1.5† (−6.8 to 3.8) | 0.57 | −2.1† (−7.4 to 3.1) | 0.43 |
| Wake after sleep onset, min¶ | 33.4 (23.0) | 29.9 (20.4) | 3.5† (−2.7 to 9.7) | 0.27 | 3.2† (−3.2 to 9.7) | 0.33 |
| Stage N1, % TST¶ | 5.2 (2.1) | 4.7 (1.8) | 0.5† (−0.1 to 1.0) | 0.10 | 0.4† (−0.2 to 1.0) | 0.18 |
| Stage N2, % TST¶ | 38.2 (7.1) | 38.9 (6.8) | −0.7† (−2.7 to 1.3) | 0.51 | −0.4† (−2.5 to 1.6) | 0.69 |
| Stage N3, % TST¶ | 33.0 (6.4) | 33.9 (7.1) | −0.9† (−2.8 to 1.0) | 0.36 | −1.0† (−3.0 to 1.0) | 0.33 |
| Rapid eye movement sleep, % TST¶ | 23.6 (4.9) | 22.5 (4.5) | 1.1† (−0.2 to 2.5) | 0.11 | 1.0† (−0.1 to 2.4) | 0.14 |
| Arousal index, n/h | 9.1 (7.7 to 10.4) | 9.4 (7.6 to 10.6) | 1.02‡ (0.95 to 1.10) | 0.57 | 1.03‡ (0.95 to 1.11) | 0.47 |
| Ventilation | ||||||
| Subjects with obstructive apnea–hypopnea index ≥ 2/h | 8 (8.2%) | 11 (11.0%) | 0.73§ (0.28 to 1.89) | 0.51 | 0.51§ (0.18 to 1.48) | 0.22 |
| Subjects with obstructive apnea–hypopnea index ≥ 2/h and/or history of adenoidectomy/tonsillectomy | 23 (23.7%) | 29 (29.0%) | 0.76§ (0.40 to 1.44) | 0.40 | 0.73§ (0.38 to 1.42) | 0.35 |
| Central apnea index, n/h | 0.3 (0.1 to 0.6) | 0.3 (0.1 to 0.7) | 1.20‡ (0.91 to 1.59) | 0.19 | 1.16‡ (0.88 to 1.55) | 0.29 |
| Periodic breathing, % TST | 0.2 (0.5) | 0.1 (0.3) | 0.06† (−0.05 to 0.17) | 0.30 | 0.06† (−0.05 to 0.18) | 0.29 |
| SpO2 nadir, % | 91.8 (2.4) | 91.3 (3.5) | 0.5† (−0.3 to 1.4) | 0.21 | 0.6† (−0.3 to 1.4) | 0.19 |
| Time with SpO2 < 90%, % TST | 0.0 (0.1) | 0.3 (1.7) | −0.23† (−0.57 to 0.11) | 0.18 | −0.16† (−0.51 to 0.19) | 0.37 |
| Limb movements | ||||||
| Periodic limb movement index, n/h | 0.7 (0.0 to 7.4) | 0.6 (0.0 to 1.8) | 1.56‡ (1.01 to 2.39) | 0.043 | 1.47‡ (0.98 to 2.21) | 0.066 |
| Subjects with periodic limb movement index > 5/h | 17 (17.5%) | 11 (11.0%) | 1.72§ (0.76 to 3.89) | 0.19 | 1.62§ (0.69 to 3.85) | 0.27 |
Definition of abbreviations: CI = confidence interval; IQR = interquartile range; SpO2 = oxygen saturation as measured by pulse oximetry; TST = total sleep time.
Covariates: center, age at assessment, sex, race, maternal education.
Quantitative data shown as caffeine − placebo mean difference, estimated by a multiple linear regression model.
Indices are shown as rate ratios, caffeine/placebo, estimated by a Poisson regression model.
Dichotomized data shown as odds ratios, caffeine/placebo, estimated by a logistic regression model.
SD provided in minutes.
N = 95 for caffeine and 96 for placebo as data from several subjects with short total recording times due to power or child-related issues were excluded from sleep architecture analyses.