The most common cause of dementia is Alzheimer’s disease (AD). AD is a progressive and irreversible brain disorder. The actual cause of AD is unknown. AD slowly damages, and then destroys, a person’s memory, judgment, reasoning skills, personality, autonomy, and bodily functions.
The disease specifically affects several components of the brain. These include:
- a gradual loss of brain cells, called neurons
- damage to neurons so they no longer function properly
- the loss of neural connections—called synapses— where messages are passed from neuron to neuron
Forgetfulness: A Normal Part of Aging?
It’s normal to sometimes forget things, but as we age, it often takes longer to learn new skills or remember words, names, or where we left our glasses. Of course, this does not mean an individual has dementia. In fact, scientists have found that healthy older adults perform just as well as their young counterparts on complex and learning tests—if given extra time to complete.
However, there’s a difference between occasional forgetfulness and behavior that may be cause for concern. Not recognizing a familiar face, trouble performing common tasks (such as using the telephone or driving home); or being unable to comprehend or recall recent information are all red flags that need to be checked by a medical professional.
Who Gets AD?
Also known as late-onset Alzheimer’s disease, AD is primarily a disease of the elderly. The first noticeable symptoms can occur as early as age 60.
When AD runs in families, it’s called familial Alzheimer’s disease (FAD).
AD sometimes can affect people as young as 30. This type of AD is called early-onset AD. It is rare and affects less than one out of every 1,000 people with AD.
The underlying cause or causes of AD, and specific risk factors, remain unclear. Yet experts believe AD is likely due to a combination of environmental and genetic factors. Lifestyle choices, such as diet, exercise, and staying mentally active like learning new skills, also are factors.
About 5.3 million Americans have AD, according to the National Institutes of Health (NIH). That number will only climb as the elderly population rises.
AD is the sixth leading cause of death in the U.S. and the fifth leading in Americans age 65 and older. Worldwide, approximately 24 million people have AD.
What’s Being Done?
Scientists are working to better understand AD in order to create more effective early diagnostic tools, improve treatments, and perhaps even discover a cure. In terms of what’s immediately available, there are numerous reputable resources and services for people who suffer with AD and their loved ones and caregivers. Some current treatment options even may slow the progression of AD, however, their effectiveness varies and diminishes over time.
Intellectual activities such as playing chess or regular social interaction have been linked to a reduced risk of AD in epidemiological studies, although no causal relationship has been found.
At present, there is no definitive evidence to support that any particular measure is effective in preventing AD. Global studies of measures to prevent or delay the onset of AD have often produced inconsistent results. However, epidemiological studies have proposed relationships between certain modifiable factors, such as diet, cardiovascular risk, pharmaceutical products, or intellectual activities among others, and a population's likelihood of developing AD. Only further research, including clinical trials, will reveal whether these factors can help to prevent AD.
Although cardiovascular risk factors, such as hypercholesterolaemia, hypertension, diabetes, and smoking, are associated with a higher risk of onset and course of AD, statins, which are cholesterol lowering drugs, have not been effective in preventing or improving the course of the disease. The components of a Mediterranean diet, which include fruit and vegetables, bread, wheat and other cereals, olive oil, fish, and red wine, may all individually or together reduce the risk and course of Alzheimer's disease. The diet's beneficial cardiovascular effect has been proposed as the mechanism of action. There is limited evidence that light to moderate use of alcohol, particularly red wine, is associated with lower risk of AD.
Reviews on the use of vitamins have not found enough evidence of efficacy to recommend vitamin C, E, or folic acid with or without vitamin B12, as preventive or treatment agents in AD. Additionally vitamin E is associated with important health risks. Trials examining folic acid and other B vitamins failed to show any significant association with cognitive decline. Docosahexaenoic acid, an Omega 3 fatty acid, has not been found to slow decline.
Long-term usage of non-steroidal anti-inflammatory drug (NSAIDs) is associated with a reduced likelihood of developing AD. Human postmortem studies, in animal models, or in vitro investigations also support the notion that NSAIDs can reduce inflammation related to amyloid plaques. However trials investigating their use as palliative treatment have failed to show positive results while no prevention trial has been completed. Curcumin from the curry spice turmeric has shown some effectiveness in preventing brain damage in mouse models due to its anti-inflammatory properties. Hormone replacement therapy, although previously used, is no longer thought to prevent dementia and in some cases may even be related to it. There is inconsistent and unconvincing evidence that ginkgo has any positive effect on cognitive impairment and dementia, and a recent study concludes that it has no effect in reducing the rate of AD incidence. A 21-year study found that coffee drinkers of 3–5 cups per day at midlife had a 65% reduction in risk of dementia in late-life.
People who engage in intellectual activities such as reading, playing board games, completing crossword puzzles, playing musical instruments, or regular social interaction show a reduced risk for Alzheimer's disease. This is compatible with the cognitive reserve theory, which states that some life experiences result in more efficient neural functioning providing the individual a cognitive reserve that delays the onset of dementia manifestations. Education delays the onset of AD syndrome, but is not related to earlier death after diagnosis. Learning a second language even later in life seems to delay getting Alzheimer disease. Physical activity is also associated with a reduced risk of AD.
Two studies have shown that medical marijuana may be effective in inhibiting the progress of AD. The active ingredient in marijuana, THC, may prevent the formation of deposits in the brain associated with Alzheimer's disease. THC was found to inhibit acetylcholinesterase more effectively than commercially marketed drugs. A recent review of the clinical research has found no evidence that cannabinoids are effective in the improvement of disturbed behaviour or in the treatment of other symptoms of AD or dementia.
Some studies have shown an increased risk of developing AD with environmental factors such the intake of metals, particularly aluminium, or exposure to solvents. The quality of some of these studies has been criticised, and other studies have concluded that there is no relationship between these environmental factors and the development of AD.
While some studies suggest that extremely low frequency electromagnetic fields may increase the risk for Alzheimer's disease, reviewers found that further epidemiological and laboratory investigations of this hypothesis are needed. Smoking is a significant AD risk factor. Systemic markers of the innate immune system are risk factors for late-onset AD.