Table 1 Selection of the study population

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.

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.

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

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

5: removal of persons with missing age

three cases were removed because a subselection on age had to be made

6: restriction to persons 20+ of age at 1–1-2011

as LTC register covered only adult population, GP-dataset was restricted likewise.