Table 1.

Subject characteristics (means or proportions) in a cohort of Finnish women by sleep duration at baseline in 1975

CharacteristicDuration of sleep
≤6 h (n = 1,181)7 h (n = 3,473)8 h (n = 5,580)≥9 h (n = 1,988)All (n = 12,222)
Age at baseline (y)43.737.135.135.136.5
Age at first full-term pregnancy (y)24.624.424.524.124.4
Number of children (in women with children)2.62.32.32.22.3
Body mass index (kg/m2)23.422.722.522.722.7
Alcohol use (g/mo)134128108106116
Dizygotic twins (%)67.167.466.669.067.3
White collar and intermediate workers (%)54.566.066.161.564.2
Nulliparous women (%)38.944.445.046.644.5
Ever used oral contraceptives (%)28.333.833.733.933.2
Sedentary exercisers (%)23.316.315.718.217.0
Current smokers (%)29.426.120.920.423.1
Insufficient sleep in 1981 ≥1 h (%)31.424.819.116.521.4
Sleep quality rated poor (%)11.61.40.80.82.0