Risk of death due to COVID-19 among current and former smokers in the Netherlands: a population-based quasi-cohort study

Abstract Background Research on smoking as a risk factor for death due to COVID-19 remains inconclusive, with different studies demonstrating either an increased or decreased risk of COVID-19 death among smokers. To investigate this controversy, this study uses data from the Netherlands to assess the relationship between smoking and death due to COVID-19. Methods In this population-based quasi-cohort study, we linked pseudonymized individual data on smoking status from the 2016 and 2020 ‘Health Monitor Adults and Elderly’ in the Netherlands (n = 914 494) to data from the cause-of-death registry (n = 2962). Death due to COVID-19 in 2020 or 2021 was taken as the main outcome. Poisson regression modelling was used to calculate relative risks (RRs) and 95% CIs of death due to COVID-19 for current and former smokers compared with never smokers while adjusting for relevant confounders (age, sex, educational level, body mass index and perceived health). Results Former smokers had a higher risk of death due to COVID-19 compared with never smokers across unadjusted (RR, 2.22; 95% CI, 2.04–2.42), age–sex-adjusted (RR, 1.38; 95% CI, 1.22–1.55) and fully adjusted (RR, 1.30; 95% CI, 1.16–1.45) models. Current smokers had a slightly higher risk of death due to COVID-19 compared with never smokers after adjusting for age and sex (RR, 1.21; 95% CI, 1.00–1.48) and after full adjustment (RR, 1.08; 95% CI, 0.90–1.29), although the results were statistically non-significant. Conclusions People with a history of smoking appear to have a higher risk of death due to COVID-19. Further research is needed to investigate which underlying mechanisms may explain this.