The Respiratory Health in Northern Europe (RHINE) study is a population-based longitudinal cohort from seven Northern European centres (Reykjavik in Iceland, Bergen in Norway, Umeå, Uppsala and Gothenburg in Sweden, Aarhus in Denmark and Tartu in Estonia) . The cohort was initially recruited as part of the European Community Respiratory Health Survey (ECRHS) I stage I (https://www.ecrhs.org/). Random population samples of men and women born 1945-73 completed postal questionnaires in 1990-1994 (RHINE I, n = 21 673 participants), 1999-2001 (RHINE II, n = 16 191 participants), 2010-12 (RHINE III, n = 13 142 participants) and 2020-23 (RHINE IV).