Contrasting hypotheses, including that of a protective role of nicotine, have been generated concerning the association between smoking and the occurrence of the disease (COVID-19) caused by the SARS-CoV-2 virus. The question has attracted a lively scientific and public debate. However, the studies conducted so far are based on clinical samples, with a majority of hospital case series, thus most likely suffering from bias due to selection. The Nordic Countries (NC) are in a unique position to contribute to a substantial knowledge advancement on this question, capitalizing on a well established set of national and regional registers that allow the identification of population based cohorts with independent assessment of exposure and disease outcome. Another unique feature of the NC is the widespread use of snus among men. Since snus contains non-combustion toxicants among which nicotine the hypothesis of a specific role of this alkaloid in the risk of COVID-19 can be refined with this data.
We propose a Consortium between the Karolinska Institutet, Sweden (host institution); the Finnish Institute for Health and Welfare in Finland; and the Norwegian Institute of Public Health. Each of the participating institutions holds longitudinal datasets accrued from different population samples, complementing surveys with health care register information. In particular each country will contribute with two population-based cohorts, that in Finland and Norway also include serologic tests.
We aim to use these facilities in order to triangulate the following overreaching question: is tobacco use associated with the risk and/or prognosis of Covid-19? We aim to analyse the available data both separately and in a pooled fashion, where the two approaches can be also used to highlight the impact of different settings of the epidemic on the association, as in a natural experiment.