Dementia is caused by a variety of diseases that may result in an irreversible, gradual decline in cognitive functioning. Early diagnosis and treatment can help slow the disease’s progression.

Dementia, characterized by impairment of overall intellectual functioning, is a chronic condition and is distinct from the normal cognitive decline observed with old age. Dementia is a clinical syndrome or group of symptoms that are the outcome of disease rather than being a disease itself. Dementia is caused by a variety of diseases, with Alzheimer’s disease and vascular dementia (caused by pathologies of blood vessels in the brain) being the most common.

What is Dementia?

Dementia is defined by the loss of intellectual or cognitive abilities that are severe enough to impair social and occupational functioning. Dementia is characterized by deficits in memory, decision making, planning, and the ability to orient oneself.

Symptoms of Dementia

Symptoms of dementia appear gradually and the early signs of dementia tend to be subtle and difficult to detect. Early recognition of dementia symptoms may allow for treatment to slow down the rate of cognitive impairment.

Early signs of dementia include:

  • Memory loss: increased forgetfulness, inability to remember recent events or frequently misplacing objects
  • Reduced concentration: easily distracted
  • Difficulty communicating: trouble finding the right words
  • Difficulty following a plan or complex instructions
    Difficulties in problem-solving
  • Changes in mood or personality: increased suspiciousness, signs of confusion, depression

These early dementia symptoms become more noticeable and prominent as dementia progresses. The expression of some of the symptoms by dementia patients may differ depending on the subtype of dementia and the underlying neurobiological defects.

Cognitive Signs

Dementia is characterized by chronic symptoms of cognitive decline that worsen over time. These cognitive symptoms include:

  • Memory loss
  • Difficulty performing complex tasks involving planning and following instruction
  • Difficulties executing motor functions
  • Impairments in problem-solving and reasoning
  • Disorientation and confusion

Psychological Signs

Psychological symptoms of dementia include:

  • Agitation
  • Depression
  • Hallucinations and delusions
  • Apathy
  • Aggression

Stages of Dementia

Most types of dementia are progressive in nature with symptoms worsening over time, and can thus be categorized into different stages depending upon the deterioration of symptoms. There are a variety of different scales or rating systems used by clinicians to determine the degree of cognitive impairment in patients living with dementia.

One of the commonly used assessment scales is the Global Deterioration Scale (GDS) developed by Barry Reisberg. The Global Deterioration Scale provides the clinician with a global overview of the impairment caused by dementia in terms of cognitive decline, functional abilities and behavioral symptoms, and divides the progression of dementia into seven stages.

The Functional Assessment Staging Test (FAST) is another assessment scale that is commonly used but is solely based on the individual’s ability to function in daily life and perform various basic activities. Although both the GDS and the FAST describe the progression of dementia in seven stages, a patient classified as belonging to a specific stage in GDS may belong to a different state according to FAST. The seven stages of dementia according to the GDS are:

No Dementia

The first three stages of the GDS scale are pre-dementia stages with the third stage characterized by mild cognitive impairment.

  • Stage 1: Normal. This stage is characterized by the absence of any symptoms of cognitive or functional impairment. Mentally healthy individuals belong to this stage.
  • Stage 2: Very mild cognitive decline. This stage is characterized by complaints of being unable to remember locations of objects and recall names.
  • Stage 3: Mild cognitive decline. This stage is characterized by learning and memory deficits that become recognizable by people closely associated with the individual. This stage is characterized by functional impairments involving deficits in executive functioning, resulting in poor job performance and difficulty learning new skills.

Early Stage

Deterioration beyond the mild cognitive impairment observed in stage 3 marks the onset of dementia. Cognitive deficits become objectively recognizable at this stage.

  • Stage 4: Mild dementia. Individuals begin to show deficits in short-term memory with lapses in the ability to recall major events or the day of the week. However, in this stage of mild dementia, individuals are still able to recall their address and family names. Functional deficits also began to emerge in the ability to manage finances, pay rent and write checks correctly.


Mid-stage dementia involves a progression to moderate to moderately severe symptoms.

  • Stage 5: Moderate dementia. At this stage of moderate dementia, individuals are unable to survive independently and require assistance with daily activities like managing finances and cooking. They also start showing deficits in the ability to perform basic activities such as choosing the appropriate attire. In terms of cognitive ability, individuals at this stage are unable to recall simple details like their address or phone number of many years, but are still able to recall some major events and know the names of their spouse and children.
  • Stage 6: Moderately severe dementia. At this stage of moderately severe dementia, individuals are unable to perform even basic activities independently and show deficits in daily hygiene such as brushing teeth and bathing. Loss of bladder and bowel control also arise at this stage. Individuals with dementia require constant supervision at this stage and may require professional help. Cognitive function declines even further with a decreased ability to recall family names and recent events and experiences in their life. Emotional changes also become apparent in the form of agitation, anxiety and occasional aggression.

Late Stage

This is the final stage of the disease and involves stages leading to the death of the patient.

  • Stage 7: Severe dementia. The final stage of dementia involves speech becoming limited to a single intelligible word. This stage also involves an inability to walk and even sit independently without falling over. Dementia patients at this stage need assistance to perform all basic activities.

Causes of Dementia

Symptoms of dementia arise from damage to neurons or nerve cells in certain brain regions. This also results in aberrant communication between brain regions. Although there are a wide variety of causal factors responsible for dementia, Alzheimer’s disease, vascular dementia and dementia with Lewy bodies constitute the major forms of progressive dementia. The symptoms of dementia may vary depending upon the location of neuronal damage in the brain. Dementia may also occur due to traumatic injuries, substance abuse and nutritional deficiency.

Types of Dementias

Dementia is a clinical syndrome, generally resulting from an underlying disease. The symptoms of a particular type of dementia depend on the damage to specific brain regions that accompany the disease responsible for dementia. Although most types of dementia are progressive and irreversible, some caused by nutritional deficiencies, substance use or cerebrospinal fluid accumulation tend to be reversible.

Progressive Dementias

Progressive dementia is characterized by the continued deterioration of functional and cognitive abilities. Alzheimer’s disease is the most common form of this type of dementia.

  • Alzheimer’s Disease: Alzheimer’s disease is the most common form of dementia that is irreversible. Alzheimer’s disease involves the formation of clumps or plaques by the ?-amyloid proteins in the space between neurons in certain brain regions, as well as the formation of neurofibrillary tangles made up of the tau protein inside the neurons. The formation of these amyloid plaques and neurofibrillary tangles is toxic to neurons, resulting in the degeneration of neurons and disrupting the connections between neurons. Alzheimer’s disease is characterized by cognitive impairment involving memory loss, paranoia, hallucinations, loss of motor control and loss of speech.
  • Vascular Dementia: Vascular dementia or vascular cognitive impairment is caused by a reduction or blocking of blood supply to cerebral regions by blood vessels. This results in the deprivation of oxygen supply to brain cells, and subsequent cell death. Vascular cognitive impairment may occur due to multiple infarcts (or strokes) that individually do not result in recognizable damage, but collectively result in brain damage and dementia. Vascular dementia may also result from brain hemorrhages caused by the bursting of arteries, or after a single stroke caused by cardiovascular disease. Symptoms of vascular dementia vary according to the region damaged by cerebrovascular disease and are often similar to Alzheimer’s disease. Besides cognitive impairment, vascular dementia may involve confusion, unsteady gait, urinary incontinence and mood changes.
  • Lewy Body Dementia: Lewy body dementia is characterized by the presence of abnormal deposits of the protein α synuclein, called Lewy bodies, in neurons. Lewy bodies are often found in the neurons that produce the neurotransmitter dopamine and can impair the functioning of these neurons. Dopamine is involved in motivated behaviors, cognition and control of movement. Formation of Lewy bodies in these neurons can cause loss of dopamine neurons and disrupt these behaviors.
  • Frontotemporal Dementia: Frontotemporal dementia is marked by the degeneration of neurons in the frontal and temporal lobes of the brain. Frontotemporal dementia may arise due to neuronal damage in either lobe or both lobes and is initially restricted to these brain regions. The frontal lobe is involved in executive functions like planning and decision making, impulse control and control of voluntary movements, whereas the temporal lobe is involved in the integration of memories, processing of emotions and language. The initial symptoms of frontotemporal dementia involve problems with decision making and planning, disinhibited social behavior, impulsive behavior and speech-related symptoms. As the neuronal degeneration spreads beyond the frontotemporal lobes, the symptoms also become more varied.
  • Mixed Dementia: Mixed dementia is characterized by the presence of more than one of the above diseases that result in dementia. Alzheimer’s disease and vascular dementia are the most common forms of dementia that occur at the same time.

Other Disorders Linked to Dementia

Besides the aforementioned types of dementia, other disorders can result in neuronal damage as well as dementia.

  • Huntington’s Disease: Huntington’s disease is caused by a mutation in a single gene that codes for the protein huntingtin. Huntington’s disease is characterized by atrophy of the subcortical brain region called the basal ganglia, which is involved in movement control. The extent of neuronal degeneration also includes other regions, resulting in deficits not only in movement control, but also encompassing cognitive abilities like attention, planning, problem solving and visuospatial abilities.
  • Traumatic Brain Injury (TBI): The most frequently observed cases of traumatic brain injury occur due to falls, car crashes or impact of an object. Traumatic brain injury can result in cognitive deficits related to learning and memory, speech deficits and motor problems. Besides causing these deficits, moderate and severe TBI is associated with dementia and can increase the risk of late-life dementia by two to four times. TBI can also result in the accumulation of amyloid plaques and tau neurofibrillary tangles that are observed in Alzheimer’s disease.
  • Parkinson’s Disease: Parkinson’s disease is characterized by a loss of dopamine neurons in brain regions that are involved in motor control. The initial symptoms are mostly related to motor movements including difficulty performing movements, terminating movements once started, tremors while at rest and muscle stiffness. However, Parkinson’s disease in the later stages involves neuronal damage in other areas, causing dementia.
  • Normal Pressure Hydrocephalus: Normal pressure hydrocephalus involves the accumulation of excessive cerebrospinal fluid (CSF) in the brain ventricles. The excessive amount of CSF exerts pressure on the surrounding brain tissue and can cause damage resulting in cognitive and motor deficits similar to Alzheimer’s disease.
  • Creutzfeldt-Jakob Disease: Creutzfeldt-Jakob disease is caused by the abnormal folding of the prion protein that is predominantly expressed in the central nervous system. In many cases, how the disease is acquired remains unknown. However, in a relatively small number of cases, it is caused by genetic factors or by exposure to medical devices or meat-related products that contain the misfolded prion. Creutzfeldt-Jakob disease results in dementia that progresses very quickly and results in a decline in cognitive function and involuntary muscle movements.
  • Wernicke-Korsakoff Syndrome: Wernicke-Korsakoff syndrome is characterized by dementia caused by vitamin B1 or thiamine deficiency. Thiamine is necessary for neurons to utilize sugar and its deficiency can lead to neuronal damage. Although thiamine deficiency is mostly related to alcohol abuse, it is also observed as a result of certain cancers, chronic infection and malnutrition. Symptoms include difficulties in learning new information, memory deficits and confabulation.

Risk Factors for Dementia

Studies over the years have identified a number of factors that increase the likelihood of dementia. Some of these factors cannot be controlled and include:

  • Age: The likelihood of occurrence of dementia increases significantly after reaching 65 years of age, with age being the strongest risk factor for dementia. The chances of dementia also tend to double every 5 years after the age of 65.
  • Family History: Studies have shown that possessing certain genes increases the risk of Alzheimer’s disease and other types of dementia. Although a genetic component is involved in the causation of dementia, many individuals with a family history of Alzheimer’s disease do not develop dementia and vice-versa. In other words, except for a small number of cases where genes play a causal role (less than 5%), the presence of certain genes can increase the risk of the disease but are not sufficient to cause dementia.
  • Down Syndrome: Individuals with Down syndrome are born with an extra copy of chromosome 21. This chromosome carries the gene that codes the amyloid precursor protein that is involved in the formation of β- amyloid plaques observed in Alzheimer’s disease. Down syndrome and dementia can happen because the presence of the extra chromosome may result in over-expression of this gene and thus increase the risk of Alzheimer’s disease. Most individuals with Down syndrome show accumulation of amyloid plaques and tau neurofibrillary tangles associated with Alzheimer’s disease by the time they reach 40.

Preventing Dementia

Besides risk factors that cannot be modified, other factors, including lifestyle and health choices, may influence the risk of cognitive impairment and dementia in later life.

  • Cardiovascular factors: Various factors such as smoking, hypertension and diabetes, that affect cardiovascular health, are associated with a higher risk of dementia. The risk of dementia is higher in individuals with systolic blood pressure higher than 160mm Hg relative to those with normal blood pressure (110-139 mm Hg).
  • Oral Health: Poor oral health leading to tooth loss may result in impaired ability to chew. This may result in the intake of a low-fiber diet rich in saturated fats and cholesterol and lacking essential micronutrients. A high-fat and high-sugar diet is associated with cognitive impairment, and oral health may thus indirectly contribute to dementia. Periodontitis involves inflammation of the gums and other tissue surrounding teeth that results in tooth loss. Periodontitis is known to result in an inflammatory response in the entire body that may contribute to cognitive decline.
  • Physical Exercise: Regular physical exercise in mid-life is associated with a reduced risk of Alzheimer’s disease and other dementias. Physical exercise, especially aerobic exercise, is associated with improved cognitive functioning in adults with mild cognitive impairment.
  • Diet: Eating a healthy diet over a long period of time is associated with a lower risk of dementia. A Mediterranean diet is rich in vegetables, fruits, legumes and cereals with a moderate intake of oily fish and dairy and is low in saturated fat and sugar intake. Higher adherence to a Mediterranean diet is associated with a reduced risk for cognitive impairment. Dietary supplements may also modestly lower the risk of dementia. For example, a higher intake of foods rich in vitamin E and greater fish and omega-3 fatty acid intake has been reported to lower the risk of cognitive decline. However, conflicting reports suggest minimal benefits from such supplements.
  • Cholesterol: Mid-life, but not late-life, serum cholesterol levels are associated with an increased risk for Alzheimer’s disease and other dementias. Higher serum cholesterol levels are associated with cardiovascular diseases that can increase the risk of dementia.
  • Diabetes: Prediabetes and diabetes are associated with a higher risk of cognitive impairment and dementia. Strict diabetic control may help prevent or postpone the onset of dementia. However, the mechanism by which diabetes has an impact on the cognitive decline is poorly understood.
  • Smoking: Smoking may increase the risk of cardiovascular diseases, which is associated with a higher risk of dementia. Studies show that current smokers are at a higher risk of Alzheimer’s disease.
    Alcohol Use: Heavy alcohol use is associated with direct neurotoxic effects on the brain that could result in cognitive impairment. Although heavy alcohol use may increase the risk of dementia, low-level alcohol consumption may have a protective effect and is associated with a lower risk of dementia than those who abstain.

Diagnosing Dementia

Diagnosis of dementia requires that the individual shows cognitive decline along with impairment in social and occupational functioning. These deficits should not be explained by alternative causes including depression, abnormal thyroid function, normal pressure hydrocephalus and vitamin deficiency. Other causes are generally ruled out by taking into account the individual’s use of medications, conducting blood test (to rule out the role of the thyroid gland or vitamin deficiencies) and brain imaging scans (to rule out other causes like tumors).

Diagnosis of dementia may be difficult during the initial stages. Diagnosis involves the use of a variety of assessment tools to determine changes in cognitive functioning, functional abilities and behavioral changes. One of the most widely used assessment scales is the Mini-Mental State Examination (MMSE), which measures various cognitive capacities involving memory, attention and language. Despite its widespread use, the MMSE is considered to take too long and be too difficult to interpret, besides suffering from educational and cultural biases. Many general practitioners are especially reluctant to use such scales due to the time required and their complexity.

There has been an emphasis in recent years for the development of assessment scales for use by general practitioners since individuals with cognitive impairment are most likely to address such problems to their general practitioners. The General Practitioner Assessment of Cognition (GPCOG) and the MiniCognitive Assessment Instrument (Mini-Cog) are new assessment scales that are easier to administer and are less influenced by biases. After the initial assessment, brain scans in the form of computed tomography and magnetic resonance imaging may provide further information regarding the nature of dementia. Cerebrospinal fluid and neuropsychological testing may also help determine the nature of the disease, especially in the case of Alzheimer’s disease.

Dementia Statistics

Over 46 million people in the world were estimated to live with dementia in 2015 and this number is predicted to reach 115 million by 2050. A U.K. study shows that among the different types of dementia, Alzheimer’s disease is the most prevalent, accounting for 66% of all cases, followed by vascular dementia at 20%. Around 15% live with Lewy body dementia, whereas less than 5% have frontotemporal dementia. Alzheimer’s disease is the 6th leading cause of death in the United States. Around 5.8 million Americans of all ages suffer from Alzheimer’s disease, with 5.6 million of these individuals aged over 65 according to a 2019 estimate. An older study (based on a 2005 survey) reports that around 6.4% of North Americans over the age of 60 live with dementia.

Dementia Treatment

There is no cure for dementia, but treatment is available for the management of its symptoms. There are some medications available that can help slow the rate of cognitive decline, such as cholinesterase inhibitors. Other medications, such as antipsychotics, antidepressants and sedatives are used for the treatment of psychological symptoms of depression, anxiety, paranoia and agitation. Many of the medications used for the psychological and behavioral symptoms of dementia have side effects.

Non-pharmacological approaches, such as physical therapy and music therapy, may also be effective for addressing symptoms of dementia. Cognitive training and cognitive rehabilitation are other non-pharmacological approaches being considered to ameliorate the cognitive impairments observed in dementia. These approaches involve practicing tasks that engage various cognitive capacities involved in memory, attention and problem solving carried out under appropriate guidance. This technique has promise, but the evidence of improvement in cognitive functioning is limited.

Prognosis and Life Expectancy

The course of dementia often depends on the extent of the underlying neuronal damage. With the absence of a cure and the progressive nature of the condition, dementia tends to be a terminal condition (except for reversible dementia). The average life expectancy after the initial diagnosis of Alzheimer’s disease and Lewy body dementia ranges between 8 and 10 years. The life expectancy for vascular dementia is much more variable depending on the extent of the damage caused by cerebrovascular disease. Frontotemporal dementia tends to progress relatively quickly and individuals with frontotemporal dementia may have a life expectancy anywhere between less than 2 years to 10 years.

Individuals with substance use disorders are often at an increased risk of developing dementia. Some individuals may thus simultaneously suffer from dementia and substance use disorder. In addition, family members of an individual with dementia may turn to substances to deal with the stress of caring for their loved one. If you or a loved one suffers from a substance abuse disorder, The Recovery Village can help. The Recovery Village specializes in the treatment of addiction along with co-occurring mood disorders. Call today to learn more about treatment options for addiction and co-occurring disorders.

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Editor – Renee Deveney
As a contributor for Advanced Recovery Systems, Renee Deveney is passionate about helping people struggling with substance use disorder. With a family history of addiction, Renee is committed to opening up a proactive dialogue about substance use and mental health. Read more
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Medically Reviewed By – Dr. Deep Shukla, PhD, MS
Dr. Deep Shukla graduated with a PhD in Neuroscience from Georgia State University in December 2018. Read more

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Medical Disclaimer

The Recovery Village aims to improve the quality of life for people struggling with substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare providers.