What effect does leading a healthy lifestyle have on people with a genetic predisposition to develop dementia?Researchers Elżbieta Kuźma and David Llewellyn from the University of Exeter Medical School (UK) set out to answer this question. Their results appear in the magazineJAMAand also presented the findings in theInternational Conference of the Alzheimer’s Association 2019, which took place in Los Angeles, California.
In their study, the authors explain that while scientists know that genes and lifestyle significantly affect the risk of Alzheimer’s and the likelihood of other types of dementia, they still do not know to what extent choosing healthy lifestyles can offset the genetic risk.
For example, research has shown thatthe E4 variant of the gene that codes for apolipoprotein E increases the risk by three times if a person inherits one copy and up to 15 times if they have two copies of the gene.
However, a significant body of research also points to the fact that non-smokers are physically active, only consume alcohol in moderation, and eat a healthy diet.have a lower risk of dementia.
Therefore, to discover how lifestyle may influence genetic risk, experts examined data from196,383 participantsof European descent aged at least 60 years who did not have dementia at baseline.
Lifestyle assessment and genetic risk
Participants had been enrolled in the UK Biobank study in 2006-2010, and they were followed clinically by researchers until 2016-2017. The scientists calculated the polygenic risk score for each person. The score “captured the individual burden of common genetic variants associated with Alzheimer’s disease and dementia risk.”
The researchers considered all the genetic risk factors for dementia that studies have confirmed so far and calculated the risk according to how strongly these factors correlated with Alzheimer’s disease.
Then they divided the participants into those with “low risk (lowest quintile), intermediate (quintiles 2 to 4) and high risk (highest quintile) of dementia.
To assess the participants’ lifestyle, the researchers calculated a “weighted healthy lifestyle score” that included smoking status, exercise, diet, and alcohol consumption. The score helped classify participants into “favorable, intermediate, and unfavorable lifestyles.”
Clear conclusion: Genetics don’t make dementia inevitable
Throughout the follow-up period,1,769 cases of dementia occurred. In general,research showed that leading a healthy lifestyle was associated with a lower risk of dementia across the board, regardless of genetic risk levels.
However, eIn the high genetic risk group specifically, 1.13% of the participants with a favorable lifestyle developed dementia compared to 1.78% of those with an unfavorable lifestyle.This translates into an “absolute risk reduction for dementia from a favorable lifestyle compared to an unfavorable lifestyle of 0.65%”.
“This risk reduction implies that, if the lifestyle is causal, one case of dementia would be avoided for every 121 people for every 10 years with high genetic risk by improving their lifestyle from unfavorable to favorable,” the authors explain.
“This is the first study to look at the extent to which you can offset your genetic risk for dementia by living a healthy lifestyle.”says co-lead author Kuźma.
“Our findings are exciting as they demonstrate that we can take steps to try to offset our genetic risk for dementia. Maintaining a healthy lifestyle was associated with a reduced risk of dementia, regardless of genetic risk,” he continues.
“This research delivers a really important message that undermines a fatalistic view of dementia.Some people believe that they will inevitably develop dementia due to their genetics. However, it appears that you may be able to substantially reduce your risk of dementia by living a healthy life, “concludes Llewellyn.
What the scientific community thinks
Jessica Teeling, Professor of Experimental Neuroimmunology, University of Southampton, who was not involved in the study, commented:
“Research shows that people at high risk of developing dementia, depending on their genetics, can reduce their risk of decreasing clinical symptoms by leading a healthy lifestyle. These findings may be partly explained by anti-inflammatory effects, which support previous studies that have identified inflammation as a key factor in dementia. A critical point to note is that this is a retrospective study in people of European descent and the lifestyle score is based on self-information. Dementia is the result of a progressive neurological disease that develops over many years.This study does not tell us whether an early or later healthy lifestyle determines a reduced risk.It also doesn’t tell us whether exposure to other factors, such as chronic gum disease, influences the risk of developing dementia. Longitudinal follow-up studies are needed to address these questions. “
Tara Spiers-Jones, Program Leader at the UK Dementia Research Institute, and Deputy Director of the Center for Brain Science Discovery at the University of Edinburgh, who was not involved in the study, said:
“This study indicates that a healthy lifestyle can offset the genetic risk of developing dementia. This is a large and well-conducted study that adds to previous evidence suggesting that leading a healthy lifestyle can reduce the risk of dementia. While this well-conducted study adds to data suggesting that a healthy lifestyle can help prevent dementia in many people,it is important to remember that some people will develop dementia no matter how healthy their lifestyle is. We need more research on the brain changes that cause the diseases that underlie dementia symptoms to develop effective preventions and treatments for all people affected by dementia. “
Carol Routledge, Research Director at Alzheimer’s Research UK who was also not involved in the study, clarified:
“These important findings suggest that lifestyle changes can benefit everyone, regardless of a person’s genetic risk for Alzheimer’s disease.A healthy lifestyle includes staying physically active, eating a healthy diet, drinking within recommended guidelines, and not smoking. This is further evidence that there are things we can all do to reduce our risk of developing dementia; however, research suggests that only 34% of adults think this is possible.
“Unfortunately, since genetics still play a role in influencing the risk of Alzheimer’s disease, there will always be people who address many or all of these lifestyle factors and still develop the disease. While we cannot change genes that we inherit, this research shows that changing our lifestyle can still help stack the odds in our favor. “
Referencia: Association of Lifestyle and Genetic Risk With Incidence of Dementia Ilianna Lourida,; Eilis Hannon; Thomas J. Littlejohns; et al Kenneth M. Langa,; Elina Hyppönen,; Elżbieta Kuźma; David J. Llewellyn. JAMA. Published online July 14, 2019. DOI: doi:10.1001/jama.2019.9879
