Косова, А. Л. Chronotype, sleep length, and school achievement of 11- to 23-year-old students in northern European Russia / Borisenkov M. F., Perminova E. V., Kosova A. L. // Chronobiol. Int. - 2010. - Vol. 27. - P. 1259-1270.

Chronobiol Int Downloaded from informahealthcare.com by 217.66.146.98 on 07/23/10 For personal use only. Students’ Chronotype and Sleep Length in the North, 1265 TABLE 2 Descriptive statistics of sleep length, and chronotype in school children and college students depending on analyzed factors Factor Gradations of factor N Sleep length, h Mean **SD *MSFsc, h Mean **SD Age, yr 11 46 8.43 1.33 3.82 1.32 12 62 8.29 0.82 4.10 1.33 13 97 7.90 1.04 4.04 1.17 14 160 7.75 1.14 4.56 1.35 15 150 7.38 1.07 4.78 1.53 16 201 7.37 1.21 4.81 1.51 IV 136 7.37 1.02 5.24 1.45 18 28 7.23 0.91 5.22 1.56 19 44 6.83 1.08 5.50 1.26 20 80 6.96 1.25 5.18 1.60 21 44 6.87 1.28 5.18 1.46 22 43 7.63 1.26 5.71 1.81 23 10 7.68 1.26 4.45 1.36 16.1 ± 3.1 1101 7.48 1.20 4.95 1.20 Sex Female 655 7.50 1.17 4.80 1.43 Male 446 7.44 1.22 5.18 1.59 Place of residence0 1 102 8.20 0.89 4.32 1.01 2 380 7.46 1.14 4.38 1.39 3 276 7.37 1.15 4.74 1.23 4 343 7.49 1.24 5.78 1.55 Latitude6 South 482 7.45 1.17 4.58 1.33 North 619 7.49 1.20 5.25 1.57 Longitude' West 343 7.44 1.24 5.84 1.55 East 758 7.48 1.16 4.56 1.30 Type of settlements'4 Village 102 8.22 0.89 4.26 1.01 City 999 7.46 1.18 4.94 1.52 Achievements' 0 175 7.38 1.25 5.52 1.63 Low 147 7.49 1.26 5.28 1.65 Average 460 7.39 1.18 4.92 1.39 High 319 7.64 1.11 4.49 1.37 Note. *MSFsc = chronotype; **SD = standard deviation. °Numbers indicate settlements as in Table 1. Settlements 1, 2 were compared with settlements 3, 4. cSettlement 4 was compared with settlements 1 to 3. ^Settlement 1 was compared with settlements 2 to 4. *0 = data are absent; low = score 3-3.5; Average = score 3.6^4.5; high = score 4.6-5. influence than sleep length on achievement in both categories of students (Table 3). Sleep length and chronotype of students who did not provide data on achievement were similar to those of students with low achievement. DISCUSSION Sleep Length In the present study, we found a steady reduction of sleep duration by age in 11- to 21-yr-olds residing in northern European Russia. The n i Q H T V L I N K * } < I I { l i r * i ( i i С я ■ iг в