Table 1 Summary of demographic data, sleep and physiological variables for early (ECT) and late (LCT) chronotypes

Sample size

N = 25

N = 31

n/a

Number of testing sessions

N = 75

N = 93

n/a

Number of males/females

M = 9

M = 14

p = 0.59 (ns)^b

F = 16

F = 17

Age (years) (mean ± SD)

22.8 ± 4.5

20.8 ± 3.0

p = 0.084 (ns)^a

Height (cm)

172.5 ± 1.7

172.5 ± 1.9

p = 0.99 (ns)^a

Weight (kg)

67.7 ± 2.3

69.8 ± 2.0

p = 0.55 (ns)^a

MSF_sc (hh:mm)

02:38 ± 00:07

06:59 ± 00:12

p < 0.0001^a

Sleep onset (hh:mm)

23:03 ± 00:07

02:36 ± 00:14

p < 0.0001^a

Wake-up time (hh:mm)

06:45 ± 00:08

10:30 ± 00:14

p < 0.0001^a

Sleep duration (h)

7.69 ± 0.14

7.85 ± 0.14

p = 0.55 (ns)^a

Dim light melatonin onset (hh:mm)

20:27 ± 00:16

23:55 ± 00:26

p < 0.0001^a

Cortisol peak time (hh:mm)

07:04 ± 00:16

11:13 ± 00:23

p < 0.0001^a