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. Author manuscript; available in PMC: 2024 Mar 28.
Published in final edited form as: Environ Int. 2024 Jan 12;184:108442. doi: 10.1016/j.envint.2024.108442

Table 3.

Quartile regression effect estimates (95% CI) for the association between urinary and water fluoride concentration, and TSH, FT4, and TT4 levels in pregnant women participating in the MIREC study.

Unadjusteda Adjustedb
n B 95% CI p n B 95% CI p
TSH (log)
  MUF (mg/L) 1399 1277
     Q2 −0.04 −0.17,0.10 0.62 −0.06 −0.21,0.09 0.44
     Q3 −0.11 −0.25,0.02 0.10 −0.10 −0.26,0.06 0.22
     Q4 0.04 −0.10,0.18 0.58 0.05 −0.11,0.22 0.52
  Water fluoride (mg/L) 1348 1224
     Q2 0.08 −0.06,0.22 0.28 0.07 −0.08,0.22 0.38
     Q3 0.01 −0.13,0.16 0.88 −0.08 −0.23,0.08 0.31
     Q4 −0.03 −0.17,0.12 0.71 −0.08 −0.23,0.07 0.31
FT4 (log)
  MUF (mg/L) 1451 1312
     Q2 0.02 −0.01,0.04 0.27 0.02 −0.01,0.05 0.19
     Q3 0.01 −0.02,0.04 0.55 0.03 −0.00,0.06 0.06
     Q4 −0.01 −0.04,0.02 0.55 0.01 −0.02,0.04 0.59
  Water fluoride (mg/L) 1395 1255
     Q2 −0.03 −0.06,−0.01 0.01 −0.03 −0.06,0.00 0.06
     Q3 −0.04 −0.06,−0.01 0.01 −0.04 −0.07,−0.01 0.01
     Q4 −0.03 −0.05,0.00 0.06 −0.02 −0.05,0.00 0.10
TT4 (ng/mL)
  MUF (mg/L) 1468 1327
     Q2 1.43 −1.62,4.47 0.36 1.30 −1.92,4.52 0.43
     Q3 4.39 1.34,7.44 0.01 3.33 −0.13,6.79 0.06
     Q4 0.50 −2.55,3.55 0.75 0.59 −2.97,4.14 0.75
  Water fluoride (mg/L) 1416 1274
     Q2 3.76 0.69,6.83 0.02 1.66 −1.51,4.83 0.30
     Q3 2.20 −0.97,5.38 0.17 2.09 −1.17,5.36 0.21
     Q4 2.96 −0.18,6.10 0.07 2.00 −1.21,5.22 0.22
a

Multiple linear regression models of associations between MUFSG and water fluoride concentration, divided into quartiles, and maternal TSH, FT4, and TT4 levels, not adjusted for covariates.

b

Multiple linear regression models of associations between MUFSG and water fluoride concentration, divided into quartiles, and maternal TSH, FT4, and TT4 levels, adjusted for maternal age, level of education, pre-pregnancy BMI, race, parity, anti-Tg and anti-TPO levels, gestational age at time of blood sampling, second-hand smoke exposure, and fetal sex; study site was also adjusted in models involving MUFSG.

Q2: corresponds to results for women with MUFSG and water fluoride concentrations in the second quartile (i.e., between the 25th and 50th percentiles), relative to those with levels in the first quartile (i.e., below the 25th percentile).

Q3: corresponds to results for women with MUFSG and water fluoride concentrations in the third quartile (i.e., between the 50th and 75th percentiles), relative to those with levels in the first quartile (i.e., below the 25th percentile).

Q4: corresponds to results for women with MUFSG and water fluoride concentrations in the fourth quartile (i.e., above the 75th percentile), relative to those with levels in the first quartile (i.e., below the 25th percentile).

Abbreviations: CI= confidence interval; TSH= thyroid stimulating hormone; MUFSG= maternal urinary fluoride, standardized for specific gravity; FT4= free thyroxine; TT4= total thyroxine.