Dementia is a syndrome characterized by deterioration in cognition, resulting in impairment in the activities of daily living. Cognitive decline occurs in one or more cognitive domains.
The incidence of dementia doubles with every 6.3 year increase in age, from 3.9 per 1000 person-years at age 60-64, to 104.8 per 1000 person-years at age 90 and over.
The global number of individuals who lived with dementia increased from 20.2 million in 1990, to 43.8 million in 2016, and dementia was the fifth leading cause of death globally, accounting for 2.4 million deaths. It is thought that the number of people living with dementia will almost double every 20 years, reaching 75 million in 2030 and 131.5 million in 2050, with this increase predominantly affecting developing countries.
The majority of cases of dementia have degenerative and vascular causes. Other causes include infections, inflammatory diseases, neoplasm, toxic insults, metabolic disorders, and trauma.
An estimated 11% to 14% of dementias are caused by potentially reversible conditions; therefore, ruling out these conditions is of the utmost importance when considering a diagnosis of dementia.
A number of conditions can present in a similar way to dementia syndrome and need to be considered during the evaluation. These include delirium, depression, amnestic syndromes, aphasia, and normal aging.
- Mild cognitive impairment (MCI)
- Alzheimer dementia
- Vascular dementia
- Lewy body dementia
- Amnestic syndromes
- Frontotemporal dementia
- Parkinson disease
- Huntington disease
- Brain tumors
- Cushing syndrome
- Primary hyperparathyroidism
- Acute intermittent porphyria
- Primary hypothyroidism
- Wilson disease
- Vitamin B12 deficiency
- Traumatic brain injury
- Lyme disease
- Syphilis (late)
- Systemic lupus erythematosus
- Sjogren syndrome
- Medication use
- Normal pressure hydrocephalus
- Creutzfeldt-Jakob disease
Aarti Gupta, MBBS
Associate Professor of Clinical Psychiatry
AG declares that she has no competing interests.
Dr Aarti Gupta would like to gratefully acknowledge Dr Rajesh Tampi, Dr Sarper Taskiran, Dr Javier Lopez, and Dr Sunanda Muralee, the previous contributors to this topic. RT, ST, JL, and SM declare that they have no competing interests.
Kirsten Wilkins, MD
Associate Professor of Psychiatry
Yale School of Medicine
KW declares that she has no competing interests.
Daniel Kaufer, MD
Memory Disorders Program
Department of Neurology
University of North Carolina at Chapel Hill
DK has received research support, speaking honoraria, and consulting fees from Eisai, Forest Laboratories, Johnson & Johnson, Medivation, Novartis, Ortho-McNeil, and Pfizer.
Lawrence Whalley, MD, FRCP, FRCPsych
Professor Emeritus of Mental Health
University of Aberdeen Institute of Applied Health Sciences
LW declares that he has no competing interests.
Randolph Schiffer, MD
Cleveland Clinic Lou Ruvo Center for Brain Health
RS declares that he has no competing interests.
Alzheimer's disease and other kinds of dementia
Caring for someone with dementiaMore Patient leaflets
- Log in or subscribe to access all of BMJ Best Practice
Use of this content is subject to our disclaimer