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Table 3 Regression coefficients for key variables a

From: The association between iodine intake and semen quality among fertile men in China

 

(1)

(2)

(3)

(4)

(5)

Semen Volume b

Semen concentration b

Semen count b

Semen Motility c

Time to pregnancy

Unrainy iodine level: reference group (iodine optimal)

 Iodine deficiency

0.05* (0.03)

−0.58*** (0.05)

− 0.52*** (0.06)

0.02 (0.03)

3.49*** (0.39)

 Iodine Excess

0.06* (0.03)

−0.26*** (0.04)

−0.20*** (0.05)

− 0.02 (0.02)

1.42*** (0.28)

BMI category: reference group (normal weight)

 underweight

−0.01 (0.06)

0.05 (0.10)

0.04 (0.13)

−0.14** (0.06)

− 0.54 (0.73)

 Overweight

0.01 (0.03)

−0.04 (0.05)

−0.02 (0.13)

0.01 (0.03)

0.07 (0.36)

 Obese

0.02 (0.10)

0.40** (0.16)

0.42** (0.26)

−0.08 (0.09)

3.52*** (1.21)

Drink frequency: reference group (never drink)

 Occasional drink

0.01 (0.05)

−0.02 (0.08)

−0.00 (0.10)

− 0.07 (0.05)

−0.77 (0.73)

 Often drink

0.01 (0.02)

0.11*** (0.04)

0.13*** (0.05)

−0.03 (0.02)

0.11 (0.29)

 Smoking

−0.01 (0.02)

−0.03 (0.04)

− 0.04 (0.05)

0.01 (0.02)

1.05*** (0.31)

 Sexual abstinence duration

0.02** (0.01)

0.04*** (0.01)

0.06*** (0.01)

0.00 (0.01)

−0.19** (0.09)

 Age

0.00 (0.00)

0.01** (0.00)

0.02*** (0.01)

−0.00 (0.00)

0.04 (0.04)

 Per capita GDP

0.00* (0.00)

−0.00 (0.00)

0.00 (0.00)

−0.00** (0.00)

0.00 (0.00)

 Poor air quality

0.04 (0.03)

0.09** (0.04)

0.13*** (0.05)

−0.07*** (0.02)

1.19*** (0.30)

 Observations

1098

1098

1098

1098

1098

  1. aOther controlled variables include: education (primary school and less, middle and high school, college and above), occupation (heavy labor vs. other), and Hukou status (urban, rural and suburban)
  2. bSemen volume, semen concentration and semen count were natural-log transformed
  3. cSemen motility was a dummy indicator, with 1 indicating greater than 40%
  4. *p < 0.1, **p < 0.05, ***p < 0.01; 2. Standard errors in parentheses