Table 5 Joint association between estimate iodized salt intake and age/ exercising/ educational status on risk of thyroid nodule

  Age ≤ 60y

1270 (4.12)

368 (1.77)

1.00

  Age > 60y

123 (0.40)

94 (0.45)

2.64 (1.97–3.53)

< 0.001

  Age ≤ 60y

27,144 (87.98)

17,050 (82.03)

2.16 (1.92–2.43)

< 0.001

  Age > 60y

2316 (7.51)

3272 (15.74)

4.88 (4.29–5.54)

< 0.001

  No

576 (1.87)

327 (1.57)

1.00

  Yes

817 (2.65)

135 (0.65)

0.29 (0.23–0.37)

< 0.001

  No

10,730 (34.78)

8431 (40.56)

1.38 (1.21–1.59)

< 0.001

  Yes

18,730 (60.71)

11,891 (57.21

1.12 (0.97–1.28)

0.111

  Senior high school and below

429 (1.39)

217 (1.04)

1.00

  Undergraduate college

724 (2.35)

200 (0.96)

0.55 (0.44–0.69)

< 0.001

  Postgraduate and above

240 (0.78)

45 (0.22)

0.37 (0.26–0.53)

< 0.001

  Senior high school and below

9681 (31.38)

9272 (44.61)

1.89 (1.60–2.24)

< 0.001

  Undergraduate college

14,755 (47.82)

9056 (43.57)

1.23 (1.03–1.43)

0.022

  Postgraduate and above

5024 (16.28)

1994 (9.59)

0.79 (0.66–0.93)

0.005