8291959 Changes in night work and sickness absence before and after breast cancer diagnosis: a cohort study with register data among female public sector workers

<h3>Objective</h3> Women with breast cancer should not work night shifts due to possible tumour recovery and other risks. However, little is known whether this recommendation is followed in practice. We investigated changes in night shift work and sickness absence before and after breast cancer diagnosis and compared these women to age-, organisation-, diagnosis year, and monthly number of night shift (≥1-2/≥3) matched female controls three years before and after the diagnosis. <h3>Material and Methods</h3> We linked payroll register-based working hour and sickness absence data for 167 night shift working women (mean age 55.4 years) and their 673 matched controls (mean age 52.4 years) in the public sector with information on the timing of the first breast cancer diagnosis from the Finnish Cancer Registry (2008-2022). Unpaired two-sided two-sample t-tests were used to compare the night shift characteristics and sickness absence before and after the diagnosis. <h3>Results</h3> The percentage and number of yearly night shifts decreased more among the cases than the controls (mean change 9.5% vs. 3.6%, P=0.0024 and 19.5 vs. 7.9 days, P=0.0003) after diagnosis. Although the percentage of &gt;2 consecutive night shift spells decreased significantly more among the cases (13.5%) than controls (3.1%), the percentage of &gt;4 consecutive night shift spells did not significantly differ (3.6% vs. 1.4%). The annual number of sickness absence days increased during the first and second years after the diagnosis among the cases compared to controls. All the differences in night shift characteristics and sickness absence between the cases and controls disappeared by the second or third follow-up year. <h3>Conclusion</h3> Night shift work decreased and sickness absence increased after a breast cancer diagnosis, but differences between cases and controls diluted year by year, indicating that the recommendation to stop night work is not systematically followed. <h3>Funding</h3> Finnish Work Environment Fund.