MedicalResearch.com Interview with:
Susanna C. Larsson, PhD
Associate Professor, Karolinska Institutet,
Institute of Environmental Medicine,
MedicalResearch.com: What is the background for this study?
Response: The causes of Alzheimer’s disease are largely unknown and there are currently no medical treatments that can halt or reverse its effects. This has led to growing interest in identifying risk factors for Alzheimer’s that are amenable to modification. Several observational studies have found that education and various lifestyle and vascular risk factors are associated with the risk of Alzheimer’s disease, but whether these factors actually cause Alzheimer’s is unclear.
We used a genetic epidemiologic method known as ‘Mendelian randomization’. This method involves the use of genes with an impact on the modifiable risk factor – for example, genes linked to education or intelligence – and assessing whether these genes are also associated with the disease. If a gene with an impact on the modifiable risk factor is also associated with the disease, then this provides strong evidence that the risk factor is a cause of the disease.
MedicalResearch.com: What are the main findings?
Response: Our results, based on aggregated genetic data from 17 000 Alzheimer’s disease patients and 37 000 healthy controls, revealed that genetic variants that predict higher education were clearly associated with a reduced risk of Alzheimer’s disease. A possible explanation for this link is ‘cognitive reserve’, which refers to the ability to recruit and use alternative brain networks or structures not normally used to compensate for brain ageing. Previous research has shown that high education increases this reserve.
We found suggestive evidence for possible associations of intelligence, circulating vitamin D, coffee consumption, and smoking with risk of Alzheimer’s disease. There was no evidence for a causal link with other modifiable factors, such as vascular risk factors.
MedicalResearch.com: What should readers take away from your report?
Response: Our study provides further evidence that higher education may lower the risk of Alzheimer’s disease.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: Research is needed to elucidate whether cognitive reserve can be increased by cognitive and social activities in later life and whether such activities reduce the risk of Alzheimer’s disease.
Larsson SC, Traylor M, Malik R, Dichgans M, Burgess S, Markus HS; CoSTREAM Consortium, on behalf of the International Genomics of Alzheimer’s Project. Modifiable pathways in Alzheimer’s disease: Mendelian randomisation analysis. BMJ 2017;359:j5375.
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