Table 1

Seasonal differences in sleep
Season for attending the study
Polar night Spring Polar Day Autumn p3
Mean sleep duration 7.12 (0.96)1 7.17 (1.00)1 7.15 (1.01)1 7.14 (1.01)1 0.20
Usually suffering from sleeplessness during Polar night 420 (14.0)2 261 (14.3)2 136 (10.1)2 271 (9.8) 2 0.008
Current sleeping problems 278 (9.4)2 79 (4.4)2 74 (5.6)2 134 (4.9)2 <0.001
-rather more than usual 223 (7.5) 69 (3.8) 62 (4.7) 116 (4.3) <0.001
-much more than usual 55 (1.9) 10 (0.6) 12 (0.9) 18 (0.7) <0.001

1Mean sleep duration in hours (SD).

2Number (%).

3Kruskal-Wallis test

Johnsen et al.

Johnsen et al. BMC Psychiatry 2012 12:225   doi:10.1186/1471-244X-12-225

Open Data