Table 2 Multiple linear regression model of Hcy on level of 5-MeTHF in all participants and stratified by MTHFR C677T genotype (5-MeTHF ≤ 10 ng/mL only)

 Continuous

1840

13.8 (11.4, 17.5)

−0.50 (− 0.69, − 0.31)

<  0.001

  Q1 (< 2.7)

460

15.3 (12.7, 20.1)

Ref

  Q2 (2.7 - < 4.4)

460

14.6 (11.7, 18.1)

−2.18 (−3.32, −1.03)

<  0.001

  Q3 (4.4 - < 6.4)

459

13.3 (11.3, 16.7)

−2.51 (− 3.71, − 1.31)

<  0.001

  Q4 (≥ 6.4)

461

12.5 (10.5, 15.2)

−3.62 (−4.87, − 2.38)

<  0.001

 P for trend

<  0.001

 Continuous

485

12.9 (10.8, 15.4)

−0.14 (−0.30, 0.02)

0.087

  Q1 (<  2.8)

121

14.0 (11.4, 16.2)

Ref

  Q2 (2.8 - < 4.5)

121

12.9 (11.1, 15.5)

−0.22 (− 1.20, 0.76)

0.662

  Q3 (4.5 - < 6.5)

121

12.3 (10.5, 14.7)

−0.47 (− 1.48, 0.53)

0.353

  Q4 (≥ 6.5)

122

12.5 (10.3, 14.6)

−0.98 (− 2.04, 0.08)

0.070

 P for trend

0.061

 Continuous

869

13.3 (11.2, 16.5)

−0.20 (− 0.35, − 0.05)

0.011

  Q1 (< 2.7)

217

14.7 (12.5, 18.1)

Ref

  Q2 (2.7 - < 4.5)

217

14.1 (11.5, 16.9)

−0.64 (− 1.54, 0.27)

0.170

  Q3 (4.5 - < 6.5)

217

12.9 (11.2, 15.3)

−0.79 (− 1.73, 0.16)

0.105

  Q4 (≥ 6.5)

218

12.0 (10.1, 14.5)

−1.30 (−2.29, −0.30)

0.011

 P for trend

0.013

 Continuous

486

17.3 (13.3, 26.1)

−1.19 (− 1.77, −0.62)

<  0.001

  Q1 (< 2.7)

122

21.0 (15.8, 35.7)

Ref

  Q2 (2.7 - < 4.1)

121

17.9 (14.3, 27.4)

−5.92 (−9.46, −2.38)

0.001

  Q3 (4.1 - < 6.2)

121

17.1 (13.2, 24.5)

−7.52 (−11.22, −3.81)

<  0.001

  Q4 (≥ 6.2)

122

14.1 (11.7, 19.1)

−9.02 (−12.84, −5.20)

<  0.001

 P for trend

<  0.001