Dementia and Alzheimer’s Disease

Dementia and Alzheimer’s Disease

(called Major Neurocognitive Disorder in the DSM 5)

Dementia is a general term for a group of serious brain disorders. In medical terms it is a syndrome meaning it is a collection of signs and symptoms that tend to occur together. It is an umbrella term used to describe any significant and persistent decline in cognitive function. It differs from Mild Cognitive Impairment (MCI) in that there is significant functional impairment with dementia and the person is no longer able to live alone and function independently. Someone with MCI is not significantly functionally impaired and requires no assistance. However, since in many cases MCI eventually transitions into dementia, the person gradually becomes more and more functionally impaired and requires more assistance over time. In other words, a person typically does not convert from MCI to dementia overnight or over a matter of days unless there has been a significant medical event such as a stroke or head injury or perhaps a major surgery.

Age is the number one risk factor for dementia and Mild Cognitive Impairment with 95% of all cases of Alzheimer’s dementia occurring over the age of 65. Every day in this country approximately 10,000 people turn age 65.

Dementia is a neurological disorder characterized by the loss of cognitive abilities including memory, language skills, reasoning ability, abstract thinking, spatial ability and orientation along with personality and behavioral changes.  Dementia is caused by brain damage resulting from an event such as a traumatic brain injury or a stroke or from a progressive disease such as Alzheimer’s disease. The parts of the brain that are most affected are the association areas of the brain, which integrate sensory information, thought, memory, and purposeful behavior. When extensive damage to these areas occurs, the affected person will begin showing cognitive deficits, mild at first and gradually becoming more severe.

There are over sixty different causes for dementia. Most dementias begin gradually (months to years) as with Alzheimer’s disease, but may begin suddenly, as after a major stroke or traumatic brain injury.  The symptoms of dementia may be reversible as when the cause is a medication side effect or a correctible medical condition such as a thyroid disorder. Other potentially reversible causes include infections, toxins, nutritional deficiencies, metabolic disturbances, and even psychiatric conditions such as major depression.  However, most types of dementia are non-reversible and progressive such as with Alzheimer’s disease. It is worth noting that dementia is not the same as Alzheimer’s disease because a person can have dementia and not have Alzheimer’s disease as the cause. A person can have dementia due to vascular disease, for example, or as the result of a traumatic brain injury. However, if a person has been diagnosed with Alzheimer’s disease by a primary care physician or a neurologist, this means the patient has dementia, most likely due to Alzheimer’s disease. In this case all other possible causes have been ruled out if a thorough dementia evaluation has been conducted.

Types of Dementia:

  • Alzheimer’s Dementia (60 to 75%)
  • Lewy Body Dementia (10 to 20%)
  • Frontotemporal Dementia (Pick’s Disease) (8%)
  • Vascular Dementia (5 to 10%)

Other less common types/causes:

  • Dementia due to Head Trauma
  • Dementia due to HIV disease
  • Dementia due to Parkinson’s disease
  • Dementia due to Huntington’s disease
  • Alcohol-Induced Persisting Dementia
  • Dementia due to Creutzfedt-Jacob disease

While there are many causes for the symptoms of dementia, Alzheimer’s disease, Lewy Body Dementia, Frontotemporal Dementia, and Vascular Dementia account for over 90% percent of all dementias. Alzheimer’s disease accounts for approximately 60 to 75%. However, evolving research is showing that having only one type or cause of dementia is not common. Usually, there are more than one type or cause of dementia. For example, Alzheimer’s disease and vascular disease together or Lewy Body Dementia with the Alzheimer’s pathology of amyloid plaques and the neurofibrillary tau protein tangles are common.

Potentially Reversible Causes of Dementia:

  • Reactions to medications
  • Emotional distress or depression
  • Metabolic disturbances
  • Nutritional deficiencies
  • Endocrine abnormalities (e.g. thyroid dysfunction)
  • Infections (encephalitis, meningitis, etc.)
  • Normal pressure hydrocephalus
  • Brain tumor

(Hearing impairment can be mistaken for memory loss.)


Adapted from the following sources:

Agronin, Marc E. Alzheimer Disease and Other Dementias (3rd Edition), Lippincott Williams & Wilkins, USA, 2014.

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th Edition. APA: Washington DC, 1994

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th Edition. APA: Washington DC, 2013

Budson, Andrew E.  MD and Solomon, Paul R. PhD, Memory Loss: A Practical Guide for Clinicians Elsevier 2011.

Budson AE, Solomon PR. New criteria for Alzheimer disease and mild cognitive impairment: implications for the practicing clinician. Neurologist. 2012 Nov;18(6):356-63.

Cummings JL, Dubois B, Molinuevo JL, Scheltens P. International Work Group criteria for the diagnosis of Alzheimer disease. Med Clin North Am. 2013 May;97(3):363-8.

Dash, P. & Villemarette-Pittman, N. (2005) Alzheimer’s Disease. AAN

Kuhn, Daniel Alzheimer’s Early Stages: First Steps for families, Friends and Caregiver’s 2nd Edition, Hunter House Publishers, Alameda, CA 2003.

Loring, David W. (Editor) INS Dictionary of Neuropsychology and Clinical Neurosciences

2nd Edition Oxford University Press, New York, N.Y. 2015

Perry, Robert; McKeith, Ian, & Perry, Elaine, (Editors) Dementia with Lewy Bodies: Clinical, Pathological, and Treatment Issues Cambridge University Press, England, 1996.

Peterson, Ronald C. (Ed) Mild Cognitive Impairment: Aging to Alzheimer’s Disease Oxford University Press, USA, 2003.