It is one of the most common causes of disability among the elderly but can develop before the age of 65 when it is known as early-onset dementia or presenile dementia. Less than 1% of those with Alzheimers have gene mutations that cause a much earlier development of the disease, around the age of 45, known as early-onset Alzheimers disease. More than 95% of people with Alzheimers disease have the sporadic form (late onset, 80–90 years of age). Worldwide the cost of dementia in 2015 was put at US$818 billion. People with dementia are often physically or chemically restrained to a greater degree than necessary, raising issues of human rights. Social stigma is commonly perceived by those with the condition, and also by their caregivers. History
Until the end of the 19th century, dementia was a much broader clinical concept. It included mental illness and any type of psychosocial incapacity, including reversible conditions. Dementia at this time simply referred to anyone who had lost the ability to reason, and was applied equally to psychosis, "organic" diseases like syphilis that destroy the brain, and to the dementia associated with old age, which was attributed to "hardening of the arteries". Dementia has been referred to in medical texts since antiquity. One of the earliest known allusions to dementia is attributed to the 7th-century BC Greek philosopher Pythagoras, who divided the human lifespan into six distinct phases: 0–6 (infancy), 7–21 (adolescence), 22–49 (young adulthood), 50–62 (middle age), 63–79 (old age), and 80–death (advanced age).
Mixed dementia can mean that symptoms onset earlier, and worsen more quickly since more parts of the brain will be affected.Genetics
Although it is not very common to inherit dementia from a parent or grandparent, there are genetic linked causes of dementia. These are only a small overall portion of the overall cases of dementia, but it is possible. Other
Chronic inflammatory conditions that may affect the brain and cognition include Behçets disease, multiple sclerosis, sarcoidosis, Sjögrens syndrome, lupus, celiac disease, and non-celiac gluten sensitivity. These types of dementias can rapidly progress, but usually have a good response to early treatment. This consists of immunomodulators or steroid administration, or in certain cases, the elimination of the causative agent. A 2019 review found no association between celiac disease and dementia overall but a potential association with vascular dementia. A 2018 review found a link between celiac disease or non-celiac gluten sensitivity and cognitive impairment and that celiac disease may be associated with Alzheimers disease, vascular dementia, and frontotemporal dementia. A strict gluten-free diet started early may protect against dementia associated with gluten-related disorders.Cases of easily reversible dementia include hypothyroidism, vitamin B12 deficiency, Lyme disease, and neurosyphilis. For Lyme disease and neurosyphilis, testing should be done if risk factors are present. Because risk factors are often difficult to determine, testing for neurosyphilis and Lyme disease, as well as other mentioned factors, may be undertaken as a matter of course where dementia is suspected. : 31–32 Many other medical and neurological conditions include dementia only late in the illness.