Nurses with long durations of rotating night shifts appear to be at increased risk for coronary heart disease. But industrial shift work among women has not been well-studied.Methods
Women employed more than one year from cohorts of soft paper mills (n=3354) and pulp and paper mills (n=2278) were evaluated in this study. Mill-specific job exposure matrices for shift work and noise exposure were developed at department and job levels. Every worked year was classified for shift work as probable, possible (including shift with no nights) or not likely. Similarly, noise was classified into seven 5 dBA bins<75 dBA to >100 dBA. Here we present the cohort mortality from myocardial infarction for 1969–2013 as standardised mortality ratios (SMRs) with 95% confidence intervals (CI) compared to the general population in Sweden.Results
Fatal myocardial infarctions (n=186) were increased in the cohort of women (SMR 123, 95% CI 106–142). Those classified as probable shift work (n=2399) had an SMR of 129 (98-166) and possible shift work (n=2060) had an SMR of 118 (93-146). Women with >10 years exposure to noise >90 dBA (n=602) had an SMR of 142 (103-192). SMRs declined with lower noise and shorter duration of noise, similar for both types of paper mills.Conclusions
Shift working women in paper mills have an increased mortality from myocardial infarction, but the effect of shift work is difficult to separate from noise exposure. Probable shift work and shorter durations of noise exposure >85 dBA were still associated with elevated SMRs.