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Table 3 Crude and adjusted prevalence ratios (PRs) and 95% confidence intervals (CIs) for dental caries in relation to smoking in the household of 20,703 schoolchildren, RYUCHS, Japan

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

  Prevalence (%) Crude PR (95% CI) Adjusted PR1 (95% CI)
Decayed and/or filled teeth    
   Smoking in household    
   Never 8080/10192 (79.3) 1.00 1.00
   Former 1574/1888 (83.4) 1.05 (1.03, 1.08) 1.03 (1.00, 1.05)
   Current <152 4403/5215 (84.4) 1.07 (1.05, 1.08) 1.04 (1.02, 1.05)
   Current ≥152 2915/3408 (85.5) 1.08 (1.06, 1.10) 1.04 (1.03, 1.06)
   P for trend   < 0.0001 < 0.0001
   Pack-years of passive smoking in household   
   None 8080/10192 (79.3) 1.00 1.00
   0.1-2.9 2827/3352 (84.3) 1.06 (1.05, 1.08) 1.03 (1.02, 1.05)
   3.0-6.9 2935/3490 (84.1) 1.06 (1.04, 1.08) 1.03 (1.01, 1.05)
   ≥7.0 3130/3669 (85.3) 1.08 (1.06, 1.09) 1.04 (1.03, 1.06)
   P for trend   < 0.0001 < 0.0001
Decayed teeth   
   Smoking in household   
   Never 4394/10192 (43.1) 1.00 1.00
   Former 944/1888 (50.0) 1.16 (1.10, 1.22) 1.06 (1.02, 1.11)
   Current <152 2797/5215 (53.6) 1.24 (1.20, 1.29) 1.10 (1.06, 1.13)
   Current ≥152 1889/3408 (55.4) 1.29 (1.24, 1.33) 1.10 (1.07, 1.14)
   P for trend   <0.0001 <0.0001
   Pack-years of passive smoking in household   
   None 4394/10192 (43.1) 1.00 1.00
   0.1-2.9 1717/3352 (51.2) 1.19 (1.14, 1.24) 1.06 (1.03, 1.10)
   3.0-6.9 1943/3490 (55.7) 1.29 (1.24, 1.34) 1.13 (1.10, 1.17)
   ≥7.0 1790/3669 (53.7) 1.25 (1.20, 1.29) 1.11 (1.08, 1.15)
   P for trend   <0.0001 <0.0001
Filled teeth   
   Smoking in household   
   Never 6974/10192 (68.4) 1.00 1.00
   Former 1305/1888 (69.1) 1.01 (0.98, 1.04) 1.00 (0.97, 1.04)
   Current <152 3623/5215 (69.5) 1.02 (0.99, 1.04) 1.01 (0.99, 1.04)
   Current ≥152 2362/3408 (69.3) 1.01 (0.99, 1.04) 1.01 (0.98, 1.04)
   P for trend   0.18 0.31
   Pack-years of passive smoking in household   
   None 6974/10192 (68.4) 1.00 1.00
   0.1-2.9 2376/3352 (70.9) 1.04 (1.01, 1.06) 1.03 (1.01, 1.06)
   3.0-6.9 2369/3490 (67.9) 0.99 (0.97, 1.02) 0.99 (0.96, 1.02)
   ≥7.0 2545/3669 (69.4) 1.01 (0.99, 1.04) 1.01 (0.98, 1.03)
   P for trend   0.55 0.93
  1. 1 Adjustment for sex, age, region of residence, toothbrushing frequency, use of fluoride, sugar intake, and paternal and maternal educational level.
  2. 2 Number of cigarettes smoked in the household per day.