The term "dementia" is used by the medical community to describe people with impaired intellectual capacity. Dementia is not a normal part of the aging process. Dementing conditions are caused by abnormal disease processes, and can affect younger as well as older persons.
Short- and long-term memory impairment is the most prominent symptom of dementia. It ranges from inability to learn new information, to think problems through or to complete complex tasks, to inability to remember past personal history. There may also be impairment in abstract thinking or in judgement. Dementia may disturb higher cortical function affecting language and motor activities. Personality change happens often involving either an alteration or an accentuation of paranoid, inappropriate or bizarre behaviour.
Deteriorating intellectual capacity may be caused by a variety of diseases and disorders. The major type of dementia is Alzheimer’s disease, although there are many other types, such as vascular dementia (related to vascular changes in the brain such as stroke), frontotemporal dementia (brain atrophy most pronounced in temporal and frontal cortical regions of the brain), Lewy body dementia (related to a particular protein deposit called a Lewy body) and mixed - where different types occur at the same time.
The US National Institute on Aging states that some 100 conditions which mimic serious disorders are actually reversible. These are sometimes called "pseudodementias," and are often treatable. Examples of conditions causing reversible symptoms of dementia are: (1) reactions to medications (sedatives, hypnotics, neuroleptics, antihypertensives and antiarthritic medications); (2) emotional distress (eg depression or major life changes); (3) metabolic disturbances (eg renal failure, liver failure, electrolyte imbalances, hypoglycemia, hypercalcemia, hepatic diseases or pancreatic disorders); (4) Undetected problems of vision or hearing may result in inappropriate responses, misinterpreted as dementia; (5) nutritional deficiencies; (6) endocrine abnormalities (hypothyroidism, hyperthyroidism, parathyroid disturbances or adrenal abnormalities can cause confusion which mimics dementia) (7) older persons can develop infections which produce a sudden onset of a confusional state; (8) subdural haematoma (blood clot on the surface of the brain); (9) normal pressure hydrocephalus; (10) brain tumours; (11) atherosclerosis, causing a series of small strokes occurs (multi-infarct dementia).
Late-life dementia, which is diagnosed when you are 65 years and over, is only influenced slightly by the genetics your parents passed onto you. Nine genes have been identified that either increase or decrease your risk for dementia. There is one that carries some influence: apolipoprotein E. If you have one combination (E4E4 alleles), you are at 15 times more likely to get dementia as someone with the more typical combination (E3E3). However, all other identified genes have only a small effect, with each putting you at a 20% increased or decreased risk of developing the disease. To put these genetic risks in perspective, dementia is more likely to be caused by obesity (60% more likely) or being inactive (80% more likely). These comparisons are not perfect, as it may be that genes related to dementia also relate to these lifestyle factors, but it does show how powerful lifestyle factors are.
In Australia in 2016, less than 2% of adults 65-69 years of age have a dementia diagnosis, and this rises to over 30% for those 90 years and over. The flip side of this is that nearly 70% of those aged 90 years and over don’t have dementia.
According to the Alzheimer's Association, approximately 4 million people are afflicted with Alzheimer's disease in the USA. By the year 2040, the number of persons with Alzheimer's disease may exceed 6 million.
Recent studies (reported in 2016) from Europe and the US demonstrated an individual’s risk of dementia has actually decreased over the past two decades because it appears that older adults are now more physically and cognitively healthy than their predecessors.