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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 bSemen concentration bSemen count bSemen Motility cTime to pregnancy
Unrainy iodine level: reference group (iodine optimal)
 Iodine deficiency0.05* (0.03)−0.58*** (0.05)− 0.52*** (0.06)0.02 (0.03)3.49*** (0.39)
 Iodine Excess0.06* (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)
 Overweight0.01 (0.03)−0.04 (0.05)−0.02 (0.13)0.01 (0.03)0.07 (0.36)
 Obese0.02 (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 drink0.01 (0.05)−0.02 (0.08)−0.00 (0.10)− 0.07 (0.05)−0.77 (0.73)
 Often drink0.01 (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 duration0.02** (0.01)0.04*** (0.01)0.06*** (0.01)0.00 (0.01)−0.19** (0.09)
 Age0.00 (0.00)0.01** (0.00)0.02*** (0.01)−0.00 (0.00)0.04 (0.04)
 Per capita GDP0.00* (0.00)−0.00 (0.00)0.00 (0.00)−0.00** (0.00)0.00 (0.00)
 Poor air quality0.04 (0.03)0.09** (0.04)0.13*** (0.05)−0.07*** (0.02)1.19*** (0.30)
 Observations10981098109810981098
  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