Causes of Alzheimer’s
Taken from the National Institute of Health-National Institute on Aging
Scientists don’t yet fully understand what causes Alzheimer’s disease in most people. In people with early-onset Alzheimer’s, a genetic mutation is usually the cause. Late-onset Alzheimer’s arises from a complex series of brain changes that occur over decades. The causes probably include a combination of genetic, environmental, and lifestyle factors. The importance of any one of these factors in increasing or decreasing the risk of developing Alzheimer’s may differ from person to person. Educate yourself about the healthy lifestyle factors that can reduce your risk of Alzheimer’s.
The Basics of Alzheimer’s
Scientists are conducting studies to learn more about plaques, tangles, and other biological features of Alzheimer’s disease. Findings from these studies will help in understanding the causes of Alzheimer’s and make diagnosis easier.
One of the great mysteries of Alzheimer’s disease is why it largely strikes older adults. Research on normal brain aging is shedding light on this question. For example, scientists are learning how age-related changes in the brain may harm neurons and contribute to Alzheimer’s damage. These age-related changes include atrophy (shrinking) of certain parts of the brain, inflammation, production of unstable molecules called free radicals, and mitochondrial dysfunction (a breakdown of energy production within a cell).
Most people with Alzheimer’s have the late-onset form of the disease, in which symptoms become apparent in their mid-60s. The apolipoprotein E (APOE) gene is involved in late-onset Alzheimer’s.
Also, scientists have identified a number of regions of interest in the genome (an organism’s complete set of DNA) that may increase a person’s risk for late-onset Alzheimer’s to varying degrees.
Early-onset Alzheimer’s occurs in people age 30 to 60 and represents less than 5 percent of all people with Alzheimer’s. Most cases are caused by an inherited change in one of three genes, resulting in a type known as early-onset familial Alzheimer’s disease, or FAD. For others, the disease appears to develop without any specific, known cause, much as it does for people with late-onset disease.
Most people with Down syndrome develop Alzheimer’s. This may be because people with Down syndrome have an extra copy of chromosome 21, which contains the gene that generates harmful amyloid.
Health, Environmental, and Lifestyle Factors
Research suggests that a host of factors beyond genetics may play a role in the development and course of Alzheimer’s disease. There is a great deal of interest, for example, in the relationship between cognitive decline and vascular conditions such as heart disease, stroke, and high blood pressure, as well as metabolic conditions such as diabetes and obesity. Ongoing research will help us understand whether and how reducing risk factors for these conditions may also reduce the risk of Alzheimer’s.
A nutritious diet, physical activity, social engagement, and mentally stimulating pursuits have all been associated with helping people stay healthy as they age. These factors might also help reduce the risk of cognitive decline and Alzheimer’s disease. Clinical trials are testing some of these possibilities.
Treatment of Alzheimer’s Disease
Alzheimer’s disease is complex, and it is unlikely that any one drug or other intervention can successfully treat it. Current approaches focus on helping people maintain mental function, manage behavioral symptoms, and slow or delay the symptoms of disease. Researchers hope to develop therapies targeting specific genetic, molecular, and cellular mechanisms so that the actual underlying cause of the disease can be stopped or prevented.
Maintaining Mental Function
Several medications are approved by the U.S. Food and Drug Administration to treat symptoms of Alzheimer’s. Donepezil (Aricept®), rivastigmine (Exelon®), and galantamine (Razadyne®) are used to treat mild to moderate Alzheimer’s (donepezil can be used for severe Alzheimer’s as well). Memantine (Namenda®) is used to treat moderate to severe Alzheimer’s. These drugs work by regulating neurotransmitters, the chemicals that transmit messages between neurons. They may help maintain thinking, memory, and communication skills, and help with certain behavioral problems. However, these drugs don’t change the underlying disease process. They are effective for some but not all people, and may help only for a limited time.
Common behavioral symptoms of Alzheimer’s include sleeplessness, wandering, agitation, anxiety, and aggression. Scientists are learning why these symptoms occur and are studying new treatments—drug and non-drug—to manage them. Research has shown that treating behavioral symptoms can make people with Alzheimer’s more comfortable and makes things easier for caregivers.
Looking for New Treatments
Alzheimer’s disease research has developed to a point where scientists can look beyond treating symptoms to think about addressing underlying disease processes. In ongoing clinical trials, scientists are developing and testing several possible interventions, including immunization therapy, drug therapies, cognitive training, physical activity, and treatments used for cardiovascular and diabetes.