Table 1

Characteristics of cases and controls, by sleep duration (age period 15–19)

Sleep duration (hours/night)
<77–910–
CasesControlsCasesControlsCasesControls
N17119417522726152244
Women, n (%)114 (67)130 (67)1269 (72)2001 (73)119 (78)193 (79)
Swedish, n (%)123 (71)149 (77)1396 (80)2158 (79)121 (80)172 (70)
Phase shift, mean no. of hours (SD)1.2 (1.5)1.2 (1.4)1.3 (1.1)1.3 (1.1)1.4 (1.2)1.3 (1.2)
Sleep quality, mean (SD)3.2 (1.4)3.5 (1.3)4.4 (0.8)4.4 (0.8)4.4 (0.8)4.5 (0.8)
Smoking, n (%)115 (67)105 (54)866 (49)1128 (41)71 (47)88 (36)
Mean sun exposure (SD)5.9 (1.9)6.5 (1.9)6.2 (1.8)6.5 (1.8)6.3 (1.7)6.7 (2.0)
Mean adolescent BMI, kg/m (SD)23.1 (4.1)22.6 (3.7)22.5 (3.9)21.9 (3.2)22.5 (3.9)22.0 (4.3)
Infectious mononucleosis, n (%)32 (19)27 (14)330 (19)283 (10)19 (13)27 (11)
Age at disease onset (SD)32.1 (11.2)34.9 (10.6)36.5 (10.8)
  • Sleep quality was assessed on a 5-grade scale (1=lowest quality, 5=highest quality).

  • BMI, body mass index.