Table 2 Relative risks for childhood cancer by time of maternal employment at facilities participating in the NRRW

From: Cancer in the offspring of female radiation workers: a record linkage study

 

Original data

New data

Pooled data

Variable with levels

Cases

Controls

Relative risk (95% CI) a

Cases

Controls

Relative risk (95% CI) a

Cases

Controls

Relative risk (95% CI) a

Leukaemia and NHL

 Left employment before conception and had no subsequent employmentb

No

13 855

13 858

1.0

6208

6205

1.0

20 063

20 063

1.0

Yes

4

1

4.00 (0.40, 197)

0

3

0.26 (0.00, 2.42)c

4

4

1.00 (0.19, 5.37)

 Still in employment at conception or resumed employment subsequentlyb

No

13 859

13 859

1.0

6206

6207

1.0

20 065

20 066

1.0

Yes

0

0

—

2

1

2.00 (0.10, 118)

2

1

2.00 (0.10, 118)

 Still in employment during year of diagnosisb,d

No

13 859

13 859

1.0

6207

6 208

1.0

20 066

20 067

1.0

Yes

0

0

—

1

0

1.00 (0.03, inf)c

1

0

1.00 (0.03, inf)c

All cancers other than leukaemia and NHL

 Left employment before conception and had no subsequent employmentb

No

21 782

21 788

1.0

10 755

10 754

1.0

32 537

32 542

1.0

Yes

7

1

7.00 (0.90, 315)e

1

2

0.50 (0.01, 9.60)

8

3

2.67 (0.64, 16)

 Still in employment at conception or resumed employment subsequentlyb

No

21 785

21 788

1.0

10 755

10 755

1.0

32 540

32 543

1.0

Yes

4

1

4.00 (0.40, 197)

1

1

1.00 (0.01, 79)

5

2

2.50 (0.40, 26)

 Still in employment during year of diagnosisb,d

No

21 788

21 788

1.0

10 755

10 755

1.0

32 543

32 543

1.0

Yes

1

1

1.00 (0.01, 79)

1

1

1.00 (0.01, 79)

2

2

1.00 (0.07, 14)

All childhood cancers

 Left employment before conception and had no subsequent employmentb

No

35 637

35 646

1.0

16 963

16 959

1.0

52 600

52 605

1.0

Yes

11

2

5.50 (1.20, 51)f

1

5

0.20 (0.004, 1.79)

12

7

1.71 (0.62, 5.14)

 Still in employment at conception or resumed employment subsequentlyb

No

35 644

35 647

1.0

16 961

16 962

1.0

52 605

52 609

1.0

Yes

4

1

4.00 (0.40, 197)

3

2

1.50 (0.17, 18)

7

3

2.33 (0.53, 14)

 Still in employment during year of diagnosisb,d

No

35 647

35 647

1.0

16 962

16 963

1.0

52 609

52 610

1.0

Yes

1

1

1.00 (0.01, 79)

2

1

2.00 (0.10, 118)

3

2

1.50 (0.17, 18)

  1. aExact 95% CI, calculated using LogXact (2005).
  2. bWith a non-zero preconceptional radiation dose recorded with NRRW.
  3. Conditional maximum-likelihood estimate is not available because the sufficient statistic is at one extreme of its range. The median unbiased point estimate is shown with 95% confidence interval (CI), see Appendix B1 of Muirhead et al (2009) for a fuller description of the statistical methodology.
  4. dRefers to 1st January in the year in which the case child was diagnosed.
  5. P=0.07.
  6. P<0.05.
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