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Table 1 Distribution of selected characteristics in 20,703 schoolchildren, RYUCHS, Japan

From: Household smoking and dental caries in schoolchildren: the Ryukyus Child Health Study

Variable n (%)
Male sex 10,201 (49.3)
Age (y)  
   6-8    6,088 (29.4)
   9-11    7,522 (36.3)
   12-15    7,092 (34.3)
Region of residence  
   Nago city    3,540 (17.1)
   Naha city 17,163 (82.9)
Toothbrushing frequency (times/day)  
   <1    1,566 (7.6)
   1    4,518 (21.8)
   2 11,925 (57.6)
   ≥3    2,694 (13.0)
Use of fluoride  
   No    4,531 (21.9)
   Yes 16,172 (78.1)
Paternal educational level  
   Junior high school    1,540 (7.4)
   High school    9,160 (44.2)
   Junior college or vocational technical school    3,097 (15.0)
   University    6,906 (33.4)
Maternal educational level  
   Junior high school    1,024 (5.0)
   High school    9,071 (43.8)
   Junior college or vocational technical school    8,704 (42.0)
   University    1,904 (9.2)
Daily sugar intake (g/1,000 kcal)  
   <3.0200 5,176 (25.0)
   3.0200-4.6510 5,176 (25.0)
   4.6511-6.8298 5,176 (25.0)
   ≥6.8299 5,175 (25.0)