Table 1 Characteristics of subjects included in the present study at each of the four measurement points. Persons with missing data on sleep length are excluded
From: Changes in self-reported sleep duration with age - a 36-year longitudinal study of Finnish adults
Year of questionnaire | Number of individuals | Women (%) | Age (mean ± 1.96 x Standard deviation) in years Range of age (birth years) |
|---|---|---|---|
1975 | 30,915 | 51.4 | 35.7 ± 14.6 18–95 (1880–1957) |
1981 | 24,535 | 51.7 | 40.5 ± 13.7 24–101 (1880–1957) |
1990 | 12,450 | 54.4 | 43.9 ± 7.8 33–60 (1930–1957) |
2011 | 8334 | 55.4 | 59.7 ± 3.7 54–66 (1945–1957) |