Table 1 Summary metrics for average sleep and light for Regular and Irregular groups.

From: Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing

Variable

Regular

Irregular

p-value

Sleep duration (h)

Clock Day

0.17 ± 0.14

1.31 ± 0.77

p < 0.0001

Biological Day

1.07 ± 0.95

1.37 ± 0.67

p = 0.12

Clock Night

6.61 ± 0.44

5.01 ± 0.91

p < 0.0002

Biological Night

5.71 ± 1.17

4.96 ± 0.83

p = 0.06

Illuminance (lux)

Clock Day

207 ± 92

128 ± 84

p = 0.03

Biological Day

200 ± 87

104 ± 61

p = 0.01

Clock Night

38 ± 30

39 ± 47

p = 0.79

Biological Night

14 ± 8

54 ± 96

p = 0.15

Normalized illuminance

Clock Day

1.70 ± 0.20

1.55 ± 0.25

p = 0.01

Biological Day

1.63 ± 0.05

1.36 ± 0.30

p = 0.001

Clock Night

0.30 ± 0.20

0.45 ± 0.25

p = 0.09

Biological Night

0.12 ± 0.07

0.50 ± 0.42

p = 0.001

  1. Values for each group are mean ± standard deviation. Clock Day is 10:00 to 22:00, Clock Night is 22:00 to 10:00. Biological Night is salivary dim light melatonin onset (DLMO) to DLMO + 10 h (i.e., 10 h after DLMO). Biological Day is DLMO + 10 h to DLMO. Normalized illuminance is illuminance divided by the individual’s average daily illuminance. A nonparametric statistical test (ranksum) was used to test for differences between groups.
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