Name: Alzheimer's Disease & Dementia -
Published: 2026-02-16T00:00:00Z

Dementia

A clinical syndrome characterized by impairment of ≥1 cognitive function that includes memory, orientation, calculation, language, judgment, executive function, visuo-spatial function and visuo-motor speed
Usually accompanied or preceded by deterioration in emotional control, social behavior or motivation and sleep disturbances
Consciousness not affected at early stage
May be due to various etiologies, such as Alzheimer’s disease, cerebrovascular disease, other neurodegenerative conditions (eg Parkinson's disease dementia [PDD], dementia with Lewy bodies [DLB]) and other diseases affecting the brain
Severity and global nature of cognitive impairment and the accompanying functional disability differentiate it from the relatively mild and variable cognitive decline associated with normal aging

Alzheimer’s Disease

Most common cause of dementia
Majority are sporadic cases which usually present at ≥65 years of age while familial types are rare and present in <65 years (early-onset dementia)
Short-term memory loss is the most common early symptom
Other spheres of cognitive impairment manifest after several years
After memory loss, loss of executive function, language dysfunction, personality and behavioral changes, increasing difficulty with activities of daily living and loss of visuo-spatial function are experienced
Neuropsychiatric symptoms (eg depression, irritability, anxiety, apathy, agitation, aggression) are common
Seizures and myoclonus may also manifest late in the disease
Sleep disturbances (eg insomnia, irregular sleep-wake rhythm disorder, restless leg syndrome, periodic limb movement disorder, rapid eye movement disorder, circadian rhythm disturbances, sleep apnea, nocturnal stridor, excessive daytime sleepiness) are common

Vascular Dementia

Reported to be the second most common cause of dementia
Dementia caused by the effects of cerebrovascular disease on cognitive functioning
May present with an abrupt onset and stepwise progression
Suspected in patients with a history of stroke or those with focal neurological signs and symptoms
Cognitive deficits will depend on what part of the brain is affected by vascular lesions
Prominent impairment of executive functions is the hallmark of the disease
May also present subacutely and insidiously with apraxia, progressive decline in gait, attention and planning in the presence of vascular pathology
Frequently coexists with Alzheimer’s disease (known as mixed dementia), characterized by a gradual progressive dementia occurring in the setting of known cerebrovascular disease
Young-onset vascular dementia may have a genetic origin

Dementia with Lewy Bodies (DLB)

Characterized by dementia and parkinsonian features (eg bradykinesia, rigidity and/or postural instability leading to frequent falls), fluctuating cognition, prominent and recurrent visual hallucinations and has more rapid evolution of symptoms than Alzheimer's disease
- Patients tend to have more problems with executive functions such as planning, prioritizing and sequencing, visuo-spatial function impairment but perform better with verbal memory
Supportive features include neuroleptic sensitivity, repeated falls and syncope or transient loss of consciousness
Onset of cognitive symptoms in relation to motor slowing is ≤1 year
Important to recognize due to high incidence of life-threatening reactions to antipsychotic medications, particularly the extrapyramidal side effects

Parkinson’s Disease Dementia (PDD)

Approximately 3 quarters of older patients with Parkinson’s disease develop dementia after 10 years
Characterized by cognitive and motor slowing, memory impairment and executive dysfunction
It is difficult to differentiate between DLB and PDD clinically
- Onset of dementia and parkinsonism in DLB must occur within a year, whereas motoric dysfunction occurs years before dementia (10-15 years) in PDD
Timing of onset of cognitive symptoms in relation to motor symptoms is >1 year
Please see Parkinson’s Disease and Parkinson’s Disease Dementia disease management chart for further information

Fronto-temporal Dementia (FTD)

Also known as fronto-temporal lobar degeneration
Patients usually present at ages 50-60 and represents a significant proportion of people who present with dementia under the age of 65
In early stages, patients present with changes in personality, deterioration of social skills, emotional blunting, early language disturbance, executive dysfunction and significant apathy
- Patients present with progressive decline in inter-personal skills, loss of emotional responsivity, and with emergence of abnormal behaviors such as disinhibition, obsessions, rituals, stereotypies, and alterations in feeding and other appetitive functions
Memory difficulties, apraxia and other features of dementia usually follow later as the disease progresses
Brain computed tomography (CT)/magnetic resonance imaging (MRI) will show frontal lobe or anterior temporal atrophy and single-photon emission computed tomography (SPECT) or positron emission tomography (PET) will show frontal hypoperfusion or hypometabolism
Course of the disease is progressive and more rapid than Alzheimer's disease

Huntington's Disease

Autosomal dominant disease affecting the basal ganglia and other subcortical structures
Manifests with motor (chorea), mood, behavioral and cognitive symptoms

Creutzfeldt-Jakob disease

An estimated 50 million people globally are living with dementia according to the World Health Organization (WHO) and projected to reach 82 million in 2030
- Estimated number of people living with dementia in Asia is 22.9 million, 9.4 million in the Americas, 10.5 million in Europe and 4 million in Africa
In most countries, the age-standardized prevalence of dementia ranges from 5-7%
- In people ≥60 years old, the estimated prevalence of dementia ranges from 4.7% in Central Europe to 8.7% in North Africa and the Middle East

Pathogenesis of Alzheimer’s disease remains unclear but it appears that there is an overproduction and/or decreased clearance of amyloid beta peptides; it also involves hyperphosphorylation of tau (a microtubule-associated protein that aids in microtubule assembly)
Extracellular beta-amyloid plaques and intracellular neurofibrillary tangles are the essential neuropathologic changes in Alzheimer’s disease

Etiology of Dementia

Irreversible causes
- Degenerative diseases (eg Alzheimer’s disease, Parkinson's disease, FTD, and DLB)
- Cerebrovascular disease (eg stroke, small-vessel disease)
- Genetic disorders (eg Down syndrome)

Alzheimer's Disease & Dementia Signs and Symptoms