Figure 1

Formation of the study population. The FIN-D2D area covers the hospital districts of South Ostrobothnia, Central Finland, Pirkanmaa, Northern Ostrobothnia, and Northern Savo (light grey colour on the map and in the boxes), and the control area covers Northern Karelia, Kainuu, Turku and Loimaa region, and the cities of Helsinki and Vantaa (dark grey colour on the map and in the boxes)