Textbox 1.

Variables included from GPs electronic medical records (EMRs) and from The NorwegianPrescription database (NorPD).

	From the EMR system	From the NorPD
GP and practice variables
Unique identifier	✓	✓
Year of birth	✓	✓
Gender	✓	✓
GP specialist	✓	✓
Solo/center practice	✓
City/rural practice	✓
Number of annual consultations	✓
Number of listed patients	✓
Number of listed patients age 70+	✓
Patient related variables
Unique patient identifier*	✓	✓
Year of birth	✓	✓
Gender	✓	✓
Date of GP-patient consultation	✓
Consultation type	✓
Date of prescription	✓
Date medication dispensed from pharmacy		✓
Medication ATC code	✓	✓
Medication strength	✓	✓
Medication package size	✓	✓
Medication number of packages	✓	✓

^*Different in the EMR and the NorPD.