Among participants with, both, a high genetic risk and an unfavorable lifestyle, 1.78% (95% CI, 1.38%-2.28%) developed dementia compared to 0.56% (95% CI, 0.48%-0.66%) of participants categorized as having a low genetic risk and favorable lifestyle (HR, 2.83; 95% CI, 2.09-3.83).
Investigators from the University of Exeter found that risk of dementia was 32% lower in people with a genetic risk but healthy lifestyle and that patients with a high genetic risk and an unfavorable lifestyle were almost 3 times as likely to develop dementia.
The underlying mechanisms aren't entirely clear, though there are several plausible hypotheses, Llewellyn said from Los Angeles, where he presented his group's work at the Alzheimer's Association International Conference. Genetic information from the UK Biobank was available for the 196,383 adults in this study who were of European ancestry, at least 60 years old and without dementia at the study baseline.
The adults who took part in the study joined it from 2006 to 2010 and researchers followed up with them until 2016 to 2017.
The brain also has to clear away debris and protein abnormalities that, in large enough amounts, can be toxic and lead to the tangles and plaques linked to Alzheimer's disease.
Participants with high genetic risk and a bad lifestyle were nearly three times more likely to develop dementia compared to those with a low genetic risk and favourable lifestyle, according to the study. Each genetic risk factor was weighted according to the strength of its association with Alzheimer's disease. Studies have combined lifestyle factors to create a composite lifestyle score to investigate the relationship between lifestyle factors and other health conditions, such as cardiovascular disease and diabetes. These were based on a self-reported survey on their diet, exercise, alcohol consumption, and smoking.
To assess lifestyle, the researchers looked at the participants' self-reported diet, physical activity, smoking and alcohol consumption. But, as the old saying goes, "Genetics loads the gun; lifestyle pulls the trigger".
"However, it appears that you may be able to substantially reduce your dementia risk by living a healthy lifestyle".
She said: "Our findings are exciting as they show that we can take action to try to offset our genetic risk for dementia. Sticking to a healthy lifestyle was associated with a reduced risk of dementia, regardless of the genetic risk", Elzbieta Kuźma, a research fellow at the University of Exeter Medical School, said in a statement.
There are some limitations to the study.
This means the benefit of adopting a healthy lifestyle is likely to be highest for those with the worst genes.
The findings challenge the often fatalistic view of the memory-robbing illness, researchers said, and add to emerging theories that whatever is good for the heart is most probably good for the brain.
The signs and symptoms of Alzheimer's disease (AD) may manifest in a person's mid-60s.
According to a 2019 report by the Alzheimer's Association, there are now 5.8 million Americans living with Alzheimer's, and this number is expected to more than double by 2050. Alzheimer's is the sixth leading cause of death in the United States and the number of cases is increasing.