Dementia is the name of a group of neurodegenerative disorders, of which Alzheimer’s disease is the most common type, that can cause cognitive impairment and behavioral and physical changes. Most cases of dementia are not hereditary, but in certain cases and with certain types of the disease, there are some genetic links.

Is Alzheimer’s disease hereditary?

In almost all cases, Alzheimer’s disease is not genetic, especially if the onset of the condition occurs after the age of 65, known as late onset Alzheimer’s disease. It is estimated to be inherited from a parent with the condition in under 1% of occurrences [1].

So, if you have a parent or grandparent with Alzheimer’s disease who is over this age, your risk of developing Alzheimer’s is no higher than someone who does not have a relative with the condition.

However, early onset Alzheimer’s disease, occurring between 30-65 years old, can be caused by a mutated gene. Early onset Alzheimer’s is rare and is seen in fewer than 10% of people with the condition. If you have a parent with this faulty gene, your risk of inheriting the responsible gene is 50%. For people with the mutated gene, there is a very high chance of developing Alzheimer’s [2].

Is vascular dementia hereditary?

Generally, vascular dementia cannot be passed from a parent to their child. However, certain underlying health conditions can cause or increase the risk of vascular dementia, such as diabetes, stroke, and high blood pressure. The risk of these conditions can be passed genetically, so there is a chance a parent could pass on to their child a gene that can contribute to the risk of developing vascular dementia [3].

Fortunately, the chance of these health issues occurring can be mitigated by maintaining a healthy lifestyle, so you can reduce your risk of vascular dementia by ensuring you look after your physical health [4].  

Is Lewy body dementia hereditary?

In a small percentage of cases, Lewy body dementia is hereditary, if it develops from a gene mutation. It has been found that there are 5 potential genetic mutations involved in Lewy body, some of which share similar mutations found in either Alzheimer’s or Parkinson’s disease [5].

The gene variation can be inherited from a parent, which does increase the risk of Lewy body dementia, but does not mean that the disease will definitely develop [6].

Is frontotemporal dementia hereditary?

Unlike most other types of dementia, frontotemporal dementia does have a strong genetic component [7]. Frontotemporal dementia is much less common than other forms of dementia and can develop at a slightly earlier age, between 45 and 60 years old [8].

Research suggests that between 20-50% of people with frontotemporal dementia have a family history of the disease [9], suggesting that it can be hereditary, if passed via a mutated gene. For all other cases, the cause is not known, but is not believed to be related to genetic causes.

Are any other types of dementia hereditary?

Huntington disease

Huntington disease is almost always inherited, with only very rare cases of the disease developing in a person with no familial history [10].

The disease develops from a mutation in the HTT gene, which can be passed to offspring. If one parent has a HTT gene mutation, the child has a 50% chance of inheriting this gene variation, which, if inherited, will lead to the development of Huntington disease in most cases [1].

People who have a mutation in the HTT gene but do not have Huntington disease, can still pass this gene to their offspring, who will then have an increased risk of developing the disease [10].

Prion disease

Prion disease is a very rare group of disorders that reportedly occur in just one person per million. Most forms of prion disease are not hereditary, while others, around 10-15%, are genetically inherited and are known as familial prion disease [11].

As with other hereditary neurodegenerative diseases, familial prion disease is caused by a mutated gene. If one parent has this gene mutation, their offspring has a 50% chance of inheriting this gene, and so will have an increased risk of developing prion disease [1].

How to reduce your risk of dementia

While we cannot change our genes, there are things we can do to help reduce our chances of developing certain types of dementia. There is no definitive way of preventing these diseases, but certain behaviors and actions can help to keep you healthy, thereby reducing your risk of cognitive decline and conditions that are associated with the development of dementia [12].

  • Look after your health: conditions such as high blood pressure and diabetes can considerably increase the risk of certain types of dementia, so keeping physically healthy can help to reduce these risk factors.
  • Exercise: exercise can reduce the risk of obesity, high blood pressure, and stroke, thereby reducing your dementia risk.
  • Eat healthily: eating a healthy, balanced diet can contribute to physical and mental health, both of which are important in reducing the risk of dementia.
  • Limit nicotine and alcohol: alcohol and smoking can contribute to poor physical and mental health, increasing the risk of high blood pressure, stroke, lung disease, memory impairment, and mood disorders.
  • Mental stimulation: keep your brain active to prevent cognitive decline, by reading, playing games, engaging in stimulating conversations, learning, and creating.
  • Social engagement: being socially active can help contribute to mental stimulation as well as decreasing loneliness and isolation, so having an active social life can help to reduce your risk of dementia.

Resources:

  1. Is Dementia Hereditary?(n.d). Alzheimer's Society. Retrieved from https://www.alzheimers.org.uk/about-dementia/risk-factors-and-prevention/is-dementia-hereditary
  2. National Institute on Aging. (Reviewed 2019). Causes of Alzheimer's Disease.NIH. Retrieved from https://www.nia.nih.gov/health/alzheimers-disease-genetics-fact-sheet
  3. Murray, M. E., Meschia, J. F., Dickson, D. W., & Ross, O. A. (2010). Genetics of Vascular Dementia. Minerva Psichiatrica, 51(1), 9–25. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4332411/
  4. National Institute on Aging. (n.d). What is Vascular Dementia?Alzheimers.gov. Retrieved from https://www.alzheimers.gov/alzheimers-dementias/vascular-dementia
  5. National Institutes of Health. (2021). Genetic Study of Lewy Body Dementia Supports Ties to Alzheimer's and Parkinson's Diseases.NIH. Retrieved from https://www.nih.gov/news-events/news-releases/genetic-study-lewy-body-dementia-supports-ties-alzheimers-parkinsons-diseases
  6. National Library of Medicine. (Updated 2021). Dementia with Lewy Bodies.MedlinePlus. Retrieved from https://medlineplus.gov/genetics/condition/dementia-with-lewy-bodies/
  7. Greaves, C. V., & Rohrer, J. D. (2019). An update on genetic frontotemporal dementia. Journal of Neurology, 266(8), 2075–2086. Retrieved from https://doi.org/10.1007/s00415-019-09363-4
  8. National Institute on Aging. (Reviewed 2021). What are Frontotemporal Disorders?NIH. Retrieved from https://www.nia.nih.gov/health/what-are-frontotemporal-disorders
  9. Olszewska, D. A., Lonergan, R., Fallon, E. M., & Lynch, T. (2016). Genetics of Frontotemporal Dementia. Current Neurology and Neuroscience Reports, 16(12), 107. Retrieved from https://doi.org/10.1007/s11910-016-0707-9
  10. National Library of Medicine. (Updated 2020). Huntington Disease.MedlinePlus. Retrieved from https://medlineplus.gov/genetics/condition/huntington-disease/
  11. National Library of Medicine. (Updated 2014). Prion Disease.MedlinePlus. Retrieved from https://medlineplus.gov/genetics/condition/prion-disease/
  12. National Institute on Aging. (n.d). Can I Prevent Dementia?Alzheimers.gov. Retrieved from https://www.alzheimers.gov/life-with-dementia/can-i-prevent-dementia