Alzheimer's disease is by far the most common dementia

The word dementia is derived from the Latin words de ("out of") and mens ("the mind") but is now defined as a brain disorder that includes memory loss, deficits in cognition (thinking, planning, and organizing abilities), a decline in emotional control or motivation, and changes in social behavior (such as increased irritability, apathy, or problems interacting with other people).

Alzheimer's disease (also referred to as dementia of the Alzheimer's type), which affects roughly 5 million Americans and more than 35 million people around the world, is by far the most common dementia. About 50 percent to 56 percent of people with dementia are diagnosed with Alzheimer's, while another 13 percent to 17 percent carry that diagnosis plus a related disorder, vascular dementia.

Here's a brief review of the most common dementia syndromes in the elderly:

ALZHEIMER'S DISEASE

Alzheimer's is distinguished from other dementias by the presence of beta-amyloid plaques outside neurons and neurofibrillary tangles within neurons. Although such lesions may be present in any aging brain, in people with Alzheimer's these lesions tend to be more numerous and accumulate in areas of the brain involved in learning and memory.

The leading theory is that the damage to the brain results from inflammation and other biological changes that cause synaptic loss and malfunction, disrupting communication between brain cells. Eventually, the brain cells die, causing tissue loss. In imaging scans, brain shrinkage is usually first noticeable in the hippocampus, which plays a central role in memory function.

The hallmark symptom of Alzheimer's is difficulty in recalling new information. As Alzheimer's progresses, memory loss disrupts daily life (for example, the person may get lost in a previously familiar neighborhood). The patient may also experience a decline in cognitive ability (finding it hard to make decisions, solve problems, or make good judgments), and may undergo significant changes in mood and personality (such as becoming more irritable, hostile, or apathetic). Alzheimer's is severely debilitating, and death usually occurs within three to nine years after diagnosis.

Five drugs have been approved for treating Alzheimer's, but they alleviate symptoms only slightly when used alone. Four are cholinesterase inhibitors that correct a neurotransmitter deficiency that may contribute to memory problems; donepezil (Aricept), galantamine (Razadyne), rivastigmine (Exelon), and tacrine (Cognex). (The last one is rarely used because it may cause severe liver problems.) The fifth drug is memantine (Namenda), which blocks the action of glutamate, a neurotransmitter that usually activates neurons but in excessive amounts can destroy them.

A 2008 study suggested that combining one of the cholinesterase inhibitors with memantine may work better than a cholinesterase inhibitor alone, though the benefits remain modest. A patient with Alzheimer's may also benefit from drugs to treat anxiety, agitation, or depression, depending on which symptoms are present.

VASCULAR DEMENTIA

This second most common type of dementia develops after one or more ischemic strokes -- blockages of blood vessels in the brain -- deprive brain cells of oxygen and cause infarcts, areas of dead tissue. Symptoms at onset depend on the type of stroke.

In the most common type of vascular dementia, brain damage results from a series of minor strokes (affecting small blood vessels) that may occur unobserved by the patient, family, or friends. The mental deterioration usually proceeds in a "stepwise" pattern, in which a person experiences a cognitive decline, seems to stabilize, then further deteriorates after another stroke. Specific symptoms may include confusion, slurred speech, or impaired thinking. This type of vascular dementia is also known as multi-infarct dementia.

Less often, vascular dementia develops after a person experiences a major stroke (one that blocks a large blood vessel and causes significant brain damage). This may cause an abrupt mental change, sometimes accompanied by paralysis or slurred speech.

Symptoms depend on the area and extent of brain damage. Thus, the cardinal feature of Alzheimer's -- memory loss -- may or may not be present in someone with vascular dementia. Likewise, specific thinking deficits may appear (such as difficulties calculating), while others (such as ability to plan) remain stable.

Once vascular dementia develops, treatment options are limited. Drugs available for Alzheimer's are sometimes prescribed but offer at best temporary and modest protection of cognition. The emphasis is therefore on preventing vascular dementia by preventing stroke. This means reinforcing healthy behaviors (avoiding smoking and limiting alcohol intake) and keeping blood pressure levels, weight, blood sugar levels, and cholesterol within healthy ranges.

In April 2010, an independent panel of experts convened by the National Institutes of Health (NIH) issued a discouraging report about whether it is possible to prevent the most common type of dementia, Alzheimer's disease. After reviewing the scientific literature and hearing presentations by researchers, panelists could not find hard evidence that any modifiable factor -- such as diet, medications, exercise, or social activity -- reduces risk of developing Alzheimer's.

Observational studies have long suggested that people who adopt heart-healthy lifestyles, such as getting regular physical activity and keeping blood pressure and cholesterol in the normal ranges, might lower their risk of Alzheimer's. But the NIH panel noted that the associations between lifestyle habits and Alzheimer's risk are weak -- and in any event do not address the crucial issue of cause and effect. As in the classic chicken-and-egg dilemma, it's hard to determine whether people remain mentally sharp as they age because they are physically healthy and socially active -- or whether those who are lucky enough to avoid Alzheimer's are therefore able to remain active as they age.

The panel has recommended more randomized controlled trials and more robust epidemiological research to provide better evidence about how to reduce risk of Alzheimer's.

MIXED DEMENTIA

A patient with mixed dementia has dementia of the Alzheimer's type plus another type of dementia, most often vascular dementia. The fact that Alzheimer's and vascular dementia often co-occur makes sense, given that atherosclerosis and vascular disease contribute to the development of both types of dementia. Unfortunately, when both occur together, the brain damage and resulting mental deterioration may be particularly severe.

Symptoms vary. They may be more typical of Alzheimer's or of the co-occurring dementia. Mixed dementia is most likely in a patient with cardiovascular disease, such as someone with high cholesterol levels, high blood pressure, or evidence of atherosclerosis, who also develops dementia.

Two cholinesterase inhibitors, galantamine and rivastigmine, have been tested in patients with mixed dementia. These drugs produced modest benefit.

LEWY BODY DEMENTIA

Lewy bodies, named for the scientist who discovered them, are abnormal deposits of alpha-synuclein -- a protein whose function is unknown -- within neurons. These lesions are also found in some patients with Alzheimer's and in those with Parkinson's disease, but are the hallmark of Lewy body dementia.

Lewy body dementia can be confirmed only through autopsy. Clinicians diagnose the condition on the basis of characteristic symptoms, including visual hallucinations, fluctuating levels of alertness during the day, and movement disorders reminiscent of Parkinson's, such as stiffness, shuffling gait, balance problems that cause falls, and lack of facial expression.

About half of those affected also have a rapid-eye-movement (REM) sleep disorder in which they thrash about while dreaming or act out their dreams. Patients may also have symptoms similar to those of Alzheimer's, such as memory problems, confusion, and other cognitive impairments.

Lewy body dementia is progressive, but patients may respond to the cholinesterase inhibitors approved for Alzheimer's. Antipsychotics are not recommended, as patients with Lewy body dementia are sensitive to them and at greater than average risk for severe side effects.

FRONTOTEMPORAL DEMENTIA

This condition develops when brain damage occurs in the front of the cerebral cortex (the frontal lobes) and the sides (the temporal lobes). The source of the damage remains unclear, although autopsies have revealed abnormal lesions known as Pick bodies that develop in the brain (a subtype known as Pick's disease). In most cases, the frontal and temporal lobes shrink as the disease progresses.

This dementia tends to have a rapid onset; symptoms appear more suddenly than in Alzheimer's or some other dementias. The disease then progresses steadily, usually first causing changes in personality and behavior. A previously polite person may start making rude remarks, for example, or a conservative spender may suddenly splurge on a questionable purchase.

The disorder may cause apathy and impair judgment or the ability to gauge other people's reactions. Memory and awareness of surroundings, however, often are spared. No treatments are available to slow progression of this dementia, and treatments available for Alzheimer's don't help. - Harvard Mental Health Letter

Available at Amazon.com:

The Most Effective Ways to Live Longer: The Surprising, Unbiased Truth About What You Should Do to Prevent Disease, Feel Great, and Have Optimum Health and Longevity

Save Your Brain: The 5 Things You Must Do to Keep Your Mind Young and Sharp

The Paleo Diet: Lose Weight and Get Healthy by Eating the Food You Were Designed to Eat

The Paleo Diet for Athletes: A Nutritional Formula for Peak Athletic Performance

 

 

(c) 2010 U.S. News and World Report