Table 5 Coefficients and confidence intervals for all covariates shown by year using simple regression.

Age

0.703

0.514-0.865

0.782

0.616-0.947

0.777

0.609-0.945

0.863

0.688-1.038

Work duration

0.055

0.043-0.066

0.059

0.047-0.071

0.058

0.046-0.070

0.065

0.053-0.077

Smoking status(no/yes)*

2.694

-0.293-5.68

1.493

-1.603-4.589

2.053

-1.071-5.178

1.445

-1.843-4.733

Group

(Firefighter/Factory worker)**

15.887

13.028-18.747

15.012

11.992-18.032

13.528

10.407-16.649

15.858

12.644-19.073