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Table 2 Univariable analysis of crude association between dental fluorosis and each explanatory variable

From: Hydrogeogenic fluoride in groundwater and dental fluorosis in Thai agrarian communities: a prevalence survey and case–control study

Variable Cases n (%) Controls n (%) Univariable model
PR 95% CI P-value
Total 132 157    
Main exposure variable
Time-averaged fluoride concentration (ppm)*
 < 0.7 7 (23.3) 23 (76.7)   Reference  
 0.7–1.49 23 (37.7) 38 (62.3) 1.62 0.78, 3.34 0.195
 ≥ 1.5 127 (64.1) 71 (35.9) 2.75 1.42, 5.31 0.003
Other explanatory variables
Sex
 Female 74 (54.4) 62 (45.6)   Reference  
 Male 83 (54.3) 70 (45.7) 1.0 0.81, 1.23 0.978
Age (year)
 < 8 48 (48.5) 51 (51.5)   Reference  
 ≥ 8 109 (57.4) 81 (42.6) 1.18 0.93, 1.50 0.165
Caregiver’s education
 ≥ Secondary school 28 (54.9) 23 (45.1)   Reference  
 < Secondary school 84 (60.0) 56 (40.0) 1.09 0.82, 1.45 0.540
Sufficiency of family income per month [≥ 26,025 THB]**
 Sufficient 6 (75.0) 2 (25.0)   Reference  
 Insufficient 112 (58.0) 81 (42.0) 0.77 0.51, 1.18 0.230
Breastfeeding
 Yes 107 (56.9) 81 (43.1)   Reference  
 No 20 (83.3) 4 (16.7) 1.46 1.18, 1.82 0.001
Brushing frequency before 2 years old
 No brushing 11 (50.0) 11 (50.0)   Reference  
 Once a day 78 (65.0) 42 (35.0) 1.30 0.84, 2.02 0.241
 ≥ 2 times a day 39 (53.4) 34 (46.6) 1.07 0.67, 1.71 0.783
Brushing frequency at ≥ 2 years old
 Once a day 35 (55.6) 28 (44.4)   Reference  
 ≥ 2 times a day 97 (60.2) 64 (39.8) 1.08 0.84, 1.40 0.532
Fluoride toothpaste use
 No 8 (66.7) 4 (33.3)   Reference  
 Yes 117 (58.8) 82 (41.2) 0.88 0.58, 1.34 0.555
Toothpaste size
 Pea-sized 54 (50.5) 53 (49.5)   Reference  
 > Pea-sized 74 (65.5) 39 (34.5) 1.30 1.03, 1.63 0.027
Fluoride supplement§
 No 95 (59.4) 65 (40.6)   Reference  
 Yes 33 (54.1) 28 (45.9) 0.91 0.70, 1.19 0.491
  1. PR, Prevalence ratio
  2. Row percentage is presented to comply with analysis of prevalence ratio
  3. Univariable model estimated by Poisson regression with robust standard error
  4. *For each child, available measures of groundwater fluoride concentrations in drinking water sources supplying the child’s residence were time-averaged over the period of birth to the survey
  5. **Average family expenditure per month in 2015, Nakhon Pathom, Thailand
  6. §Fluoride supplement was not further included in the multivariable model due to the collinearity problem