1. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Why do we age so differently? VELUX FONDEN Funded by: Social Inequality in Health – Causation and Selection: A Twin Approach Ph.D. Student Mia Madsen DARC: Odense & Copenhagen, Project start June 2008 Supervisors Kaare Christensen, Merete Osler, Anne-Marie Nybo Andersen

2. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Research question  A strong and consistent association between socioeconomic position and health is well-established, but is this association a true causal relationship or a spurious one, produced by underlying background factors?

3. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Matched on genotype (partly or fully) and childhood environment Do they differ significantly with respect to health outcomes? Discordant on adult SEP Analytical approach Causation or selection?

4. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc The principal of twin studies: Three comparisons CohortDZMZ Early environmental confounding ↑↑-- Genetic confounding↑↑↑- No confounding by genes or common environment ↑↑

5. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc The evidence so far…  Contradictory findings  Generally, no association between SEP and health when genetic constitution and rearing environment are controlled for. Osler et al. 2007, Osler et al. 2009 & Behrman et al. (work in progress) (Danish data)  Persisting association between SEP and health in intra-pair analyses (Krieger et al. 2005 & Lundborg 2008) (American data)

6. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Social Science and Medicine, 2009

7. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Evidence continued…  Societal context seems to play a role  Results seem to depend on the social indicators used  Results seem to vary according to health outcomes studied  Power limitations?  Chance findings?

8. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Editorial IJE  ”...These are important findings that now require replication in larger twin data sets using a wider range of health outcomes…” (Ebrahim, S)  Aim: In nation-wide registers to investigate the effect of different social indicators during the life course on survival and a wide range of different health outcomes in a twin population matched on early life experiences and genetic make-up (partly or fully)

9. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Data sources & information  Danish Twin Registry (1870 and onwards, N=75,000+)  Statistics Denmark (Information on all twins + 5% sample of all birth cohorts from the general population)  Health  Causes of death (1973-2006)  Hospitalizations (incl. diagnoses, operations, and accidents causing admission to hospital (1977-2004))  Cancer registry (soon)  Social data  Income (1980-2004)  Occupation (1980-2004)  Socio-economic position (1980- 2004)  Civil status (1980-2004)  Education (1980-2004)

10. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc 1st paper – initial analyses  Educational status and all cause and cause- specific mortality  Follow-up: 1980-2006  Education: 1980, International Standard of Classification (ISCED) (Primary/Secondary, Upper secondary/Post- secondary non-tertiary, Tertiary)  Mortality: All cause, CVD (+ischemic and stroke), Cancer, Smoking-related cancer, Respiratory causes, External causes, Abnormal findings/insufficiently defined symptoms

11. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Study population

12. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Descriptives, education Educational status (ISCED)N% Primary/secondary13,58548.8 Post-secondary9,76035.0 Tertiary3,98914.3 Missing5321.9 Total cohort27,866100  Discordant twin pairs  Primary/secondary & Post-secondary: N=6000 (900 MZ)  Primary/secondary & Tertiary: N=3060 (402 MZ)  Post-secondary & Tertiary: N=1456 (198 MZ)

13. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Educational status and selected causes of death Cox regression analysis

14. - D A N I S H A G I N G R E S E A R C H C E N T E R - www.sdu.dk/darc Summary of results  The effect of education seems to persist in the intrapair analyses for all cause mortality and CVD. For cancer the pattern is less clear.  Results are compatible with an independent effect of educational status in adulthood above and beyond genetic constitution and other background factors.