Many people with a family history of memory problems wonder whether they will also experience memory problems (beyond those associated with normal aging). Although there are multiple considerations in determining the hereditary risk of memory problems, two questions provide some guidance:
1. What type of memory problems does your family member have?
Because memory problems can have many underlying causes, the first step is to determine whether there is an identified reason for your family member’s memory problems. Memory problems related to a sudden medical event (such as a stroke, traumatic brain injury, or infection) or to potential reversible factors (such as depression, sleep disorders, vitamin deficiencies, or thyroid issues, among others) are generally not highly hereditary unless the underlying condition that caused the memory problems is inherited. However, memory problems related to Alzheimer’s disease, or memory problems without a clear cause and with concerning symptoms (such as forgetting well-known information, difficulty performing well-known tasks, and progressive worsening) may be more hereditary.
2. Is your family member a first- second- or third- degree relative?
A 2019 study showed that people with one first-degree relative (a parent, sibling, or child) with Alzheimer's had nearly twice the risk of developing Alzheimer's. Having two first-degree relatives was linked to a nearly 4 times greater risk, and having four first-degree relatives was linked to a 15 times greater risk. As the degree of relation becomes more distant, the hereditary risk is lower (and thus requires that more relatives have memory problems to increase your risk). For example, people with three or four second-degree relatives (grandparents, grandchildren, aunts, nieces, and nephews) with Alzheimer's were more than twice as likely to develop the disease. People with the lowest risk had no family history of the disease or only one or two third-degree relatives with the disease.
Why might a family history of Alzheimer's increase the hereditary risk of memory problems?
There is no direct genetic cause for 99 percent of cases of Alzheimer's. However, the Apolipoprotein (APOE) gene on chromosome 19 has been linked to an increased risk of Alzheimer's. The APOE gene assists with cholesterol transport and helps clear beta-amyloid protein from the brain. (Beta-amyloid protein is naturally occurring in the brains of all individuals, but has been linked to Alzheimer’s when it clumps together abnormally.)
The APOE gene has two alleles, or genetic sequences: one inherited from each parent. One of the alleles—“e4" or “epsilon 4”—is linked to a higher risk of Alzheimer's, and is present in about 20% of the population. Having one copy of the APOE e4 allele increases the risk of developing Alzheimer's two to five times, and having two copies of the allele (one from each parent, which is present in about 2% of the population) increases the risk 9 to 12 times.
However, about 50 percent of individuals with one copy of APOE e4 do not go on to develop Alzheimer’s. Conversely, the absence of genetic risk factors or a family history of memory problems isn’t a guarantee of protection against Alzheimer's. About 60 percent of people with Alzheimer's do not have a genetic risk and about 75% do not have a family history of the disease.
The fact that Alzheimer's is linked to several non-genetic factors is one of many reasons that the Alzheimer's Association does not support genetic testing to determine risk for the disease. In fact, the Alzheimer’s Association recommends, “A person genuinely concerned about their dementia risk, or the risk of a loved one, based on family history, should consider making lifestyle changes regardless of genetic status. Growing evidence indicates that people can reduce their risk of cognitive decline by adopting key lifestyle habits.”
You can minimize your risk of Alzheimer's regardless of your heredity
A recent groundbreaking randomized controlled trial—the FINGER study (the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability)—has added to a growing body of research showing that a healthy lifestyle can reduce the risk of Alzheimer's, regardless of heredity or family history. The FINGER study showed that a combination of exercise, a brain-healthy diet, cognitive training, and vascular risk management (such as improving blood pressure and cholesterol) resulted in a 30% reduction in cognitive decline after just two years. Those benefits continued for two more years after the study, and are still being tracked. Even more exciting, FINGER showed that people with the APOE e4 gene had the same level of reduced cognitive decline as those who did not have a genetic risk for Alzheimer's.
Given that the cellular changes related to Alzheimer's can develop 30 years or more before symptoms begin, it has become increasingly clear that we are unlikely to successfully treat it with a medication that is administered decades after the disease has taken hold. Years of research shows that a proactively healthy lifestyle holds the greatest promise in reducing risk of the disease. However, the vital role of lifestyle factors does not mean that people who develop Alzheimer's somehow failed to live a healthy life or are to blame for the disease. Lifestyle factors are only one piece of the Alzheimer's puzzle. In fact, there is strong evidence that individuals with Alzheimer's who had healthy habits may have delayed the expression of their symptoms, sometimes by several years.
The top 5 lifestyle factors that optimize memory
The five lifestyle factors with the greatest ability to reduce the risk of Alzheimer's include cardiovascular exercise (which not only grows new neurons, but can improve "vascular risk factors" for Alzheimer's including blood pressure, cholesterol, blood sugar, and weight), a brain healthy diet, cognitive and social engagement, lowering stress, and enhancing sleep. Individuals with a family history of memory problems or Alzheimer's may especially benefit from proactively integrating these factors to decrease the likelihood of developing a future memory problem. At first blush, these factors might seem like obvious components for any health-related plan, but the reason they are essential to highlight in the context of brain health is three-fold:
1. Identifying these factors saves you time and money by allowing you to direct your efforts toward proven strategies, and steer clear of the rapidly growing number of products and strategies that are unproven (such as brain health supplements, restrictive “brain health” diets, and most online brain games), or minimally helpful (unidimensional tools such as crosswords or sudoku puzzles that are used in lieu of other more effective lifestyle factors). This guidance can prevent a false sense of security and save years of lost time that could be spent truly improving brain health.
2. Alzheimer's is devastating, and there is no cure for the disease. Lifestyle factors offer vital hope, and are the only proven way to reduce the risk of developing Alzheimer's and/or delay the onset of symptoms. Knowing which of dozens of lifestyle factors to prioritize is key to your success.
3. The knowledge that lifestyle factors are equally as powerful for individuals with a family history of memory problems and/or a genetic risk for Alzheimer's is a game changer. This information provides hope and guidance in the context of myths that overemphasize the impact of heredity on memory.
As 2021 begins, let’s refresh our motivation to engage in a brain-healthy lifestyle, empowered by the knowledge that it is never too early and never too late to build a healthy brain, regardless of our heredity.
Cannon-Albright, L. A. Foster, N. L., Schliep, K., et al. (2019). Relative risk for Alzheimer disease based on complete family history. Neurology 92(15): e1745-53.
Rosenberg, A., Ngandu, T., Rusanen, M., et al. (2018). Multidomain lifestyle intervention benefits a large elderly population at risk for cognitive decline and dementia regardless of baseline characteristics: The FINGER trial." Alzheimer's and Dementia 14(3): 263-70
Solomon, A., Turanen, H., Ngandu, T., et al. (2018). Effect of the apolipoprotein E genotype on cognitive change during a multidomain lifestyle intervention: A subgroup analysis of a randomized clinical trial. JAMA Neurology 75(4): 462-70.
Younes, L., Albert, M., Moghekar, A., Soldan, A., Pettigrew, C., & Miller, M. I. (2019) Identifying change points in biomarkers during the preclinical phase of Alzheimer's disease. Frontiers in Aging Neuroscience 11:74.