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Is There a Direct Causal Effect of Education on Dementia? A Swedish Natural Experiment on 1.3 Million Individuals

28 Pages Posted: 24 Jan 2019

See all articles by Dominika Seblova

Dominika Seblova

Karolinska Institutet - Aging Research Centre

Martin Fischer

Research Institute of Industrial Economics (IFN); Karolinska Institutet - Aging Research Centre

Stefan Fors

Karolinska Institutet - Aging Research Centre

Kristina Johnell

Karolinska Institutet - Aging Research Centre

Martin Karlsson

University of Duisburg-Essen - CINCH

Therese Nilsson

Lund University - Department of Economics

Anna Christina Svensson

Karolinska Institutet - Department of Public Health Sciences

Martin Lövdén

Karolinska Institutet - Aging Research Centre

Anton Lager

Karolinska Institutet - Aging Research Centre

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Abstract

Background: Education is related to dementia risk. Researchers in public health often treat education as a modifiable risk factor, implying that prolonging education may reduce dementia incidence. This reasoning rests on the largely untested assumption that education has causal effects on dementia risk.    

Methods: We used variance in education induced by a compulsory schooling reform, which extended Swedish primary school (Folkskola) from 6 to 7 years as a tool for studying direct causal effects of education on dementia risk. The reform was implemented gradually in school districts and had minor spillover effects. We studied 18 birth cohorts (1920-1937), excluding individuals with unknown reform status, those who died, emigrated, or received dementia diagnosis prior to 65 years of age. The outcome was dementia diagnosis in the National Inpatient and Cause of Death Registers. The reform allowed us to study direct effects of prolonged education with high validity and statistical precision. In the main analyses, we employed sex-stratified Cox survival models with stratified baseline hazards at the school-district level, used chronological age as the time scale, and dummy-coded cohort effects.    

Findings: 1,341,842 individuals were included. The reform did not affect the risk of dementia diagnosis in a statistically significant way. The estimates and associated confidence intervals (women: HR = 1.01; 95% CI = 0.97-1.04; men: HR = 1.02; 95% CI = 0.99-1.06; all: HR = 1.01; 95% CI = 0.98-1.04) indicate that any direct effect is likely of a negligible or very small magnitude. Sensitivity analyses targeting pre-post changes, differences in healthcare-seeking behavior, and impact of exposure misclassification left results essentially unaltered.    

Interpretation: Longer education, at least in the absence of sizable spillover effects to adult socio-economic factors, cannot be uncritically assumed to substantially reduce the risk of moderate to severe dementia.  

Funding Statement: FORTE (2013-2277) and Swedish Research Council (446-2013-7189) to ML.

Declaration of Interests: The authors declare no competing interests.

Ethics Approval Statement: The study was approved by the Regional Ethical Review Board in Stockholm (Case number: 2010/1185-31/5).

Suggested Citation

Seblova, Dominika and Fischer, Martin and Fors, Stefan and Johnell, Kristina and Karlsson, Martin and Nilsson, Therese and Svensson, Anna Christina and Lövdén, Martin and Lager, Anton, Is There a Direct Causal Effect of Education on Dementia? A Swedish Natural Experiment on 1.3 Million Individuals (January 14, 2019). Available at SSRN: https://ssrn.com/abstract=3320156 or http://dx.doi.org/10.2139/ssrn.3320156

Dominika Seblova (Contact Author)

Karolinska Institutet - Aging Research Centre ( email )

Tomtebodavägen 18A, plan 9
Solna, 171 65
Sweden

Martin Fischer

Research Institute of Industrial Economics (IFN) ( email )

Box 55665
Grevgatan 34, 2nd floor
Stockholm, SE-102 15
Sweden

Karolinska Institutet - Aging Research Centre ( email )

Tomtebodavägen 18A, plan 9
Solna, 171 65
Sweden

Stefan Fors

Karolinska Institutet - Aging Research Centre

Tomtebodavägen 18A, plan 9
Solna, 171 65
Sweden

Kristina Johnell

Karolinska Institutet - Aging Research Centre

Tomtebodavägen 18A, plan 9
Solna, 171 65
Sweden

Martin Karlsson

University of Duisburg-Essen - CINCH ( email )

Universitätsstraße 2
Essen, 45141
Germany

Therese Nilsson

Lund University - Department of Economics ( email )

P.O. Box 7082
S-220 07 Lund
Sweden

Anna Christina Svensson

Karolinska Institutet - Department of Public Health Sciences

Stockholm
Sweden

Martin Lövdén

Karolinska Institutet - Aging Research Centre

Tomtebodavägen 18A, plan 9
Solna, 171 65
Sweden

Anton Lager

Karolinska Institutet - Aging Research Centre

Tomtebodavägen 18A, plan 9
Solna, 171 65
Sweden

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