Table 4.
Pearson correlation coefficients for plasma caffeine/paraxanthine concentrations and selected sleep variables
| Insomnia (n = 65) | Control (n = 29) | Whole Sample (n = 94) | |
|---|---|---|---|
| Plasma caffeine + paraxanthinea vs. | Pearson | Pearson | Pearson |
| Diary daily caffeinated beverage consumptionb | 0.54* | 0.73* (n = 28) | 0.58* (n = 93) |
| Diary estimated caffeine intakea | 0.61* (n = 51) | 0.41 (n = 21) | 0.57* (n = 72) |
| Diary sleep latencye | 0.22 (n = 64) | −0.13 | 0.09 (n = 93) |
| Diary total sleep time | −0.01 (n = 64) | −0.06 | −0.01 (n = 93) |
| Diary wake after sleep onsetb | −0.02 (n = 64) | 0.01 | −0.02 (n = 93) |
| Diary sleep efficiencyf | 0.08 (n = 64) | −0.01 | 0.02 (n = 93) |
| Diary sleep quality | −0.12 (n = 64) | −0.31 | −0.09 (n = 93) |
| Age (years) | 0.01 | -0.08 | −0.02 |
| PSG sleep latencyc | 0.10 | 0.03 | 0.08 |
| PSG total sleep time | −0.16 | 0.04 | −0.12 |
| PSG wake time after sleep onset | 0.14 | −0.23 | 0.07 |
| PSG Sleep efficiencya | −0.20 | 0.20 | −0.13 |
| Stage 1 %c | 0.32* | −0.01 | 0.23* |
| Stage 2 % | 0.12 | −0.06 | 0.07 |
| Stage 3 % | −0.14 | 0.05 | −0.10 |
| Stage 4 %a | −0.11 | 0.23 | 0.00 |
| Delta powerd | −0.05 (n = 61) | 0.29 (n = 27) | 0.03 (n = 88) |
| Sigma powerc | 0.08 (n = 61) | 0.20 (n = 27) | 0.11 (n = 88) |
| Beta powerd | 0.07 (n = 61) | 0.15 (n = 27) | 0.09 (n = 88) |
Means and standard deviations reported in the original units.
*
p < 0.05
a
SQRT(X+1) transformation used in the analyses
b
SQRT(X+.1) transformation used in the analyses
c
LN(X+1) transformation used in the analyses
d
SQRT(X) transformation used in the analyses
e
LN(X) transformation used in the analyses
f
LN(100-X) transformation used in the analyses.