Table 1.

Selection of the study population

Selection made	Explanation	Number of subjects after selection
1: all citizens registered for at least one year in GP-database between 1-1-2006 and 1–1-2011	all potentially eligible subjects in artificial cohort.	701,790
2: all patients registered for a continuous period of at least three years in GP-database	three year continuous registration necessary for establishing disease prevalence.	441,809
3: all patients alive at 1–1-2012	necessary for full follow-up in LTC register for at least one year after last recorded contact date in GP-database	427,115
4: all patients with complete medical records for 2008–2010	restriction of the analysis to GP-data 2008–2010 was necessary because LTC-utilization database was incomplete for 2007	276,721
5: removal of persons with missing age	three cases were removed because a subselection on age had to be made	276,718
6: restriction to persons 20+ of age at 1–1-2011	as LTC register covered only adult population, GP-dataset was restricted likewise.	214,821