Are familial factors underlying the association between socioeconomic position and prescription medicine? A register-based study on Danish twins.
OBJECTIVE
Although well established, the association between socioeconomic position and health and health behaviour is not clearly understood, and it has been speculated that familial factors, for example, dispositional factors or exposures in the rearing environment, may be underlying the association. The objective was to compare prescription fillings within twin pairs who are partly or fully genetically identical and share childhood exposures.


METHODS
Twin cohort study.


METHODS
Denmark.


METHODS
Data from the Danish Twin Registry were linked to registers in Statistics Denmark and the Danish Registry of Medicinal Product statistics. A total of 8582 monozygotic (MZ) and 15 788 dizygotic same sex (DZSS) twins were included.


METHODS
Number of prescription fillings during follow-up (1995-2005) was analysed according to education and income. Results of unpaired and intrapair analyses were compared.


RESULTS
An inverse social gradient in filling of prescriptions for all-purpose and system-specific drugs was observed in the unpaired analyses. In the intrapair analyses, associations were attenuated some in DZSS and more in MZ twins. Filling of drugs targeting the nervous system was still strongly associated with income in the intrapair analyses.


CONCLUSIONS
Familial factors seem to account for part of the observed social inequality in filling of prescription medicine.
Unit of Epidemiology, University of Southern Denmark, Odense, Denmark.
Mia
M
Madsen
Per Kragh
PK
Andersen
Mette
M
Gerster
Anne-Marie Nybo
AM
Andersen
Merete
M
Osler
Kaare
K
Christensen
Epidemiology; Genetics; Social Medicine