Results from multinomial logistic regression with TSH levels (low/normal/high) regressed on fluoride exposure from urine and tap water (Cycle 3 only). Pregnant women and those taking a thyroid medication were excluded from analyses
| Predictor variable | Cycle 3 of CHMS | ||||
| Unadjusted† estimates for fluoride urine subsample (RRR, 95% CI) | Adjusted‡ estimates for fluoride urine subsample (RRR, 95% CI) (n=2008) | Unadjusted† estimates for fluoride tap water subsample (RRR, 95% CI) | Adjusted‡ estimates for fluoride tap water subsample (RRR, 95% CI) (n=2000) | ||
| Urinary fluoride μmol/L) (co;nt) | Low TSH | 1.01 (0.99 to 1.04) | 1.01 (0.99 to 1.04) | – | – |
| Normal TSH (ref) | – | – | |||
| High TSH | 0.99 (0.97 to 1.02) | 0.99 (0.97 to 1.02) | |||
| Fluoride concentration of tap water (mg/L) (cont) | Low TSH | – | – | 1.77 (0.20 to 15.86) | 1.38 (0.08 to 24.49) |
| Normal TSH (ref) | – | – | |||
| High TSH | 1.38 (0.07 to 27.00) | 1.20 (0.14 to 10.08) | |||
| Sex (ref: male) | Low TSH | 1.04 (0.28 to 3.85) | 1.03 (0.26 to 4.06) | 1.03 (0.28 to 3.79) | 0.98 (0.24 to 3.92) |
| Normal TSH (ref) | – | – | – | – | |
| High TSH | 0.97 (0.15 to 6.36) | 0.89 (0.11 to 7.03) | 0.96 (0.14 to 6.31) | 0.91 (0.13 to 6.36) | |
| Age (years) (cont) | Low TSH | 1.01 (0.99 to 1.04) | 1.01 (0.98 to 1.05) | 1.01 (0.99 to 1.04) | 1.02 (0.99 to 1.05) |
| Normal TSH (ref) | – | – | – | – | |
| High TSH | 0.99 (0.97 to 1.00) | 0.99 (0.97 to 1.01) | 0.99 (0.97 to 1.00) | 0.99 (0.96 to 1.01) | |
| Household income adequacy (ref: lower and middle income) | Low TSH | 1.87 (0.71 to 4.89) | 1.97 (0.65 to 5.97) | 1.89 (0.72 to 4.97) | 1.98 (0.64 to 6.11) |
| Normal TSH (ref) | – | – | – | – | |
| High TSH | 1.66 (0.30 to 9.02) | 1.94 (0.26 to 14.50) | 1.67 (0.30 to 9.16) | 1.88 (0.26 to 13.46) | |
| Highest attained education in the household (ref: less than bachelor’s degree) | Low TSH | 0.84 (0.31 to 2.28) | 0.70 (0.22 to 2.16) | 0.85 (0.31 to 2.31) | 0.71 (0.23 to 2.19) |
| Normal TSH (ref) | – | – | – | – | |
| High TSH | 0.99 (0.10 to 10.22) | 0.80 (0.07 to 9.61) | 1.00 (0.10 to 10.39) | 0.82 (0.07 to 9.21) | |
†Column contains bivariate associations between predictor variable and the outcome (TSH level (low/normal/high)).
‡Column contains associations from single model containing all predictor variables (age, sex, household income adequacy and highest attained education in the household).
*p<0.05, **p<0.01, ***p<0.1.
Note: these models were rerun using creatinine-adjusted urinary fluoride (μmol/mmol) and no significant observations were detected (data not shown).
CHMS, Canadian Health Measures Survey; RRR, relative risk ratio; TSH, thyroid-stimulating hormone.