Table 3

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

Sleep quality (using a 5-grade scale)
Low sleep quality (1–3)High sleep quality (4–5)
CasesControlsCasesControls
N35037517252789
Women, n (%)240 (69)273 (73)1262 (73)2051 (74)
Swedish, n (%)267 (76)274 (73)1373 (80)2205 (79)
Phase shift, mean no. of hours (SD)1.3 (1.4)1.4 (1.3)1.3 (1.1)1.3 (1.1)
Sleep duration, hours/night (SD)7.4 (1.4)7.4 (1.4)8.2 (0.9)8.2 (0.9)
Smoking, n (%)198 (56)172 (46)1725 (50)1149 (41)
Mean sun exposure (SD)5.9 (1.9)6.6 (1.9)6.3 (1.7)6.5 (1.8)
Mean adolescent BMI, kg/m (SD)23.0 (4.4)22.6 (4.0)22.5 (3.8)21.8 (3.3)
Infectious mononucleosis, n (%)70 (20)42 (11)311 (18)295 (11)
Age at disease onset (SD)32.1 (10.8)35.3 (10.6)
  • BMI, body mass index.