Dementia

Dementia is a syndrome, classed as a major neurocognitive disorder often associated with neurodegenerative diseases such as Alzheimer's, and characterized by a general decline in cognitive processes that affects the ability to perform everyday activities.
This typically involves problems with memory, thinking, behavior, and motor control. Aside from memory impairment and a disruption in thought patterns, the most common symptoms of dementia include emotional problems, difficulties with language, and decreased motivation. The symptoms may be described as occurring in a continuum over several stages. Dementia is an incurable, progressive disorder, with varying degrees of severity (mild to major) and many forms or subtypes. The condition has a significant effect on the individual, their caregivers, and their social relationships in general. Dementia is not the same as age-related decline in cognition and memory, with no change in intelligence.
The most common form of dementia is Alzheimer's. Dementia can be caused by brain injuries and stroke. It has also been described as a spectrum of disorders with subtypes of dementia based on which known disorder caused its development, such as Parkinson's disease for Parkinson's disease dementia, Huntington's disease for Huntington's disease dementia, vascular disease for vascular dementia, HIV infection causing HIV dementia, frontotemporal lobar degeneration for frontotemporal dementia, Lewy body disease for dementia with Lewy bodies, and prion diseases. Subtypes of neurodegenerative dementias may also be based on the underlying pathology of misfolded proteins, such as synucleinopathies and tauopathies. The coexistence of more than one type of dementia is known as mixed dementia.
Diagnosis is usually based on history of the illness and cognitive testing with imaging. Imaging can help to determine the dementia subtype, and to exclude other causes. Blood tests are usually taken to rule out other possible reversible causes such as hypothyroidism (an underactive thyroid). Fluid biomarkers detected in cerebrospinal fluid, and in blood can identify Alzheimer's disease. PET scans can detect amyloid beta and tau, the two intrinsically disordered proteins that are the hallmark features of Alzheimer's.
Although the greatest risk factor for developing dementia is aging, dementia is not a normal part of the aging process; many people aged 90 and above show no signs of dementia. Risk factors, diagnosis and caregiving practices are influenced by cultural and socio-environmental factors. Several risk factors for dementia, such as smoking and obesity, are modifiable by lifestyle changes.
As of 2025, dementia is the seventh leading cause of death worldwide and has 10 million new cases reported every year (approximately one every three seconds). In the UK it is the leading cause of death. It is one of the main causes of disabilities in those aged over 65. There is no known cure for dementia.
Acetylcholinesterase inhibitors such as donepezil are often used in some dementia subtypes and may be beneficial in mild to moderate stages, but the overall benefit may be minor. There are many measures that can improve the quality of life of a person with dementia and their caregivers. Cognitive behavioral therapy may give some benefit for treating the associated symptoms of depression.