Yes, Alzheimer’s disease can run in families. Studies have shown that people who have a family history of the disease may be at an increased risk of developing it themselves.
There is also a genetic component to the disease, with certain genetic mutations identified that increase a person’s risk of developing Alzheimer’s.
Two categories of genes influence whether a person develops a disease: (1) risk genes and (2) deterministic genes. Researchers have identified hereditary Alzheimer’s genes in both categories.
Risk genes increase the likelihood of developing a disease but do not guarantee it will happen. Researchers have found several genes that increase the risk of Alzheimer’s. APOE-e4 is the first risk gene identified and remains the gene with strongest impact on risk. Researchers estimate that between 40-65% of people diagnosed with Alzheimer’s have the APOE-e4 gene.
APOE-e4 is one of three common forms of the APOE gene; the others are APOE-e2 and APOE-e3. We all inherit a copy of some form of APOE from each parent. Those who inherit one copy of APOE-e4 from their mother or father have an increased risk of developing Alzheimer’s. Those who inherit two copies from their mother and father have an even higher risk, but not a certainty. In addition to raising risk, APOE-e4 may tend to make symptoms appear at a younger age than usual.
An estimated 20-30% of individuals in the United States have one or two copies of APOE-e4; approximately 2% of the U.S. population has two copies of APOE-e4.
Deterministic genes directly cause a disease, guaranteeing that anyone who inherits one will develop a disorder. Scientists have found rare genes that cause Alzheimer’s in only a few hundred extended families worldwide. These genes, which are estimated to account for 1% or less of Alzheimer’s cases, cause familial early-onset forms in which symptoms usually develop between a person’s early 40s and mid-50s. The vast majority of individuals with Alzheimer’s have late-onset disease, occurring at age 65 or later.
However, it is important to note that having a family history of the disease does not necessarily mean that a person will develop it themselves.
Additionally, environmental factors and lifestyle habits may also play a role in the development of the disease.