Surprising Risk Factors of Alzheimer’s disease
Scientists have identified factors that increase the risk of Alzheimer’s disease. The most important risk factors—age, family history and heredity—can’t be changed, but emerging evidence suggests there may be other factors we can influence.
Age:The greatest known risk factor for Alzheimer’s is advancing age. For example, while one of nine people age 65 or older has this disease, nearly one of three people age 85 or older has the disease. One of the greatest mysteries of Alzheimer’s disease is why risk rises so dramatically as we grow older.
Family history:Another strong risk factor is family history. Those who have a parent, brother, sister or child with this disease are more likely to develop the disease. The risk increases if more than one family member has the illness. When diseases tend to run in families, either heredity (genetics) or environmental factors, or both, may play a role.
Genetics (heredity):Scientists know genes are involved in Alzheimer’s. There are two types of genes that can play a role in affecting whether a person develops a disease—risk genes and deterministic genes. Alzheimer’s genes have been found in both categories.
1-Risk genes increase the likelihood of developing a disease, but do not guarantee it will happen. Scientists have so far identified several risk genes implicated in this disease.
The risk gene with the strongest influence is called apolipoprotein E-e4 (APOE-e4). Scientists estimate that APOE-e4 may be a factor in 20 to 25 percent of Alzheimer’s cases.
2-Deterministic genes directly cause a disease, guaranteeing that anyone who inherits them will develop the disorder.
Scientists have discovered variations that directly cause Alzheimer’s disease in the genes coding three proteins: amyloid precursor protein (APP), presenilin-1 (PS-1) and presenilin-2 (PS-2). When Alzheimer’s disease is caused by these deterministic variations, it is called “autosomal dominant Alzheimer’s disease (ADAD)” or “familial Alzheimer’s disease,” and many family members in multiple generations are affected. Symptoms nearly always develop before age 60, and may appear as early as a person’s 30s or 40s. Deterministic Alzheimer’s variations have been found in only a few hundred extended families worldwide. True familial Alzheimer’s accounts for less than 5 percent of cases.