Association of working shifts, inside and outside of healthcare, with risk of severe COVID-19: An observational study

Background: Health and key workers are at an increased risk of developing severe COVID-19; it is not known, however, if this risk is exacerbated in those with irregular work patterns. We aimed to investigate the risk of severe COVID-19 in health and shift workers. Methods: We included UK Biobank participants in employment or self-employed at baseline and with linked COVID-19 data to 31st August 2020. Participants were grouped as neither a health worker nor shift worker (reference category), health worker only, shift worker only, or both and associations with severe COVID-19 investigated in logistic regressions. Findings: Of 235,685 participants (81.5% neither health nor shift worker, 1.4% health worker only, 16.9% shift worker only, and 0.3% both), there were 580 (0.25%) cases of severe COVID-19. The risk of severe COVID-19 was higher in health workers (adjusted odds ratio: 2.32 [95% CI: 1.33, 4.05]; shift workers (2.06 [1.72, 2.47]); and in health workers who worked shifts (7.56 [3.86, 14.79]). Being both a health worker and a shift worker had a possible greater impact on the risk severe COVID-19 in South Asian and Black and African Caribbean ethnicities compared to White individuals. Interpretation: Both health and shift work were independently associated with over twice the risk of severe COVID-19; the risk was over seven times higher in health workers who work shifts. Vaccinations, therapeutic and preventative options should take into consideration not only health and key worker status but also shift worker status.