Genetics, Cardiovascular Health Both Contribute to Dementia Risk

Dementia-associated common gene variants or the APOE e4 genotype can more than double dementia risk, but good cardiovascular health can halve dementia risk, according to a study published in Neurology.

Researchers from Boston University School of Public Health (BUSPH) and School of Medicine (BUSM) noted that because these effects are additive, genes and cardiovascular health can independently add to or subtract from a person’s risk of developing dementia.

"Just because you have a high genetic risk of dementia doesn't mean that you can't lower your risk by adopting a healthier lifestyle," said study lead author Dr. Gina Peloso, assistant professor of biostatistics at BUSPH.

Researchers used data from 1,211 participants in the offspring cohort of the BU-based Framingham Heart Study, the longest-running cardiovascular disease study in the US. The analysis included genetic information, cardiovascular health data from 1991-1995, and data from the Framingham Heart Study’s regular dementia screenings beginning in 1998-2001.

The team found that participants with a high genetic risk score based on several common gene variants were 2.6 times more likely to develop dementia than participants with a low genetic risk score. Researchers also looked separately at the dementia-associated APOE e4 genotype, which is found in ten to 15 percent of the general population.

The results showed that participants with at least one APOE e4 allele were 2.3 times more likely to develop dementia than participants without one.

Researchers noted that previous studies have suggested that cardiovascular health affects a person’s risk of dementia and Alzheimer’s. For this study, researchers scored participants on the American Heart Association’s seven components of cardiovascular health: physical activity, cholesterol, healthy diet, blood pressure, weight, blood glucose, and smoking status.

The team found that participants with a favorable cardiovascular health score were 55 percent less likely to develop dementia than participants with an unfavorable score.

The researchers did not find any interaction between genetic risk score and APOE e4 and cardiovascular health, indicating that these risk factors independently affect dementia risk.

The results demonstrate that a person’s genetics are not the only factor that determine health and well-being.

"We have long maintained that genetics is not destiny, that the impact of your family history and genetic risk can be lowered by healthy lifestyle choices,” said study senior author Dr. Sudha Seshadri, founding director of the Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases at The University of Texas Health Science Center at San Antonio.

“This is true for persons with low genetic risk and also for persons with high genetic risk of dementia, so it is never too soon and never too late to adopt a heart-healthy lifestyle."

The team noted that the study was limited by its small sample size, and the fact that the Framingham Heart Study is composed of individuals of European descent. This means that results may not be generalizable to non-European populations. Additionally, some of the genetic markers may influence both cardiovascular health and dementia.

The group noted that more research will shed light on the impact cardiovascular health and genetics have on dementia risk.

“In a community-based sample, we observed that both genetic risk and cardiovascular health are additively associated with incident dementia. Further studies are needed to replicate these results in larger as well as ethnically diverse samples,” the team concluded.