Table 2 Beta (β) and 95 % confidence interval for semen-quality parameters according to categories of serum vitamin D

Semen volume (mL)

Crude

Ref

0.004 (-0.59, 0.60)

0.67 (0.10, 1.24)

0.006

Model 1

Ref

-0.05 (-0.66, 0.55)

0.63 (0.05, 1.20)

0.008

Model 2

Ref

-0.006 (-0.61, 0.60)

0.62 (0.04, 1.19)

0.010

Model 3

Ref

0.03 (-0.57, 0.64)

0.63 (0.06, 1.20)

0.010

Sperm count (10⁶/mL)

Crude

Ref

7.32 (-3.19, 17.85)

11.83 (1.84, 21.82)

0.021

Model 1

Ref

8.57 (-2.02, 19.16)

12.71 (2.70, 22.72)

0.015

Model 2

Ref

10.03 (-0.49, 20.56)

13.23 (3.32, 23.13)

0.013

Model 3

Ref

9.99 (-0.43, 20.42)

14.40 (4.56, 24.25)

0.005

Sperm total motility (%)

Crude

Ref

13.39 (7.36, 19.43)

18.31 (12.59, 24.04)

< 0.001

Model 1

Ref

13.57 (7.48, 19.66)

18.44 (12.68, 24.20)

< 0.001

Model 2

Ref

13.82 (7.72, 19.92)

18.32 (12.58, 24.06)

< 0.001

Model 3

Ref

13.60 (7.51, 19.69)

18.12 (12.37, 23.86)

< 0.001

Normal morphology (%)

Crude

Ref

1.21 (0.26, 2.16)

2.22 (1.31, 3.12)

< 0.001

Model 1

Ref

0.93 (-0.005, 1.87)

2.02 (1.13, 2.91)

< 0.001

Model 2

Ref

1.02 (0.09, 1.95)

2.00 (1.12, 2.88)

< 0.001

Model 3

Ref

1.05 (0.12, 1.98)

1.95 (1.07, 2.83)

< 0.001