Memory and cognitive dysfunction resulting in memory loss may have different causes, some of them reversible; others like in the case of Alzheimer’s disease are not reversible. Most of the reversible memory loss presentations are secondary to treatable medical conditions. The following are some of the most frequently diagnosed non reversible disorders: 

• Alzheimer’s disease 
• Vascular / Multi infarct Dementia
• Parkinson Dementia
• Lewy Body Dementia 
• Pick’s Disease / Fronto-Temporal Dementia (FTD).

Memory and cognitive dysfunction can occur when specific parts of the brain become impaired manifesting as a decline in memory and a reduction in cognitive abilities, including: 

• Executive functioning
• Problem-solving / reasoning and decision making
• Speech/communication skills
• Social behavior

These symptoms can also range in severity with less severe conditions, such as Mild Cognitive Impairment (MCI) presenting with milder deficits and sometimes progressing slowly to more severe forms over time as in the case of Alzheimer’s disease. 

The cause of memory and cognitive function may vary from person to person; but a number of factors may contribute to the decline including: Age, Genetics, Family History, Substance and alcohol use, Cerebrovascular abnormalities, Untreated diabetes , other metabolic disorders, Cardiovascular disorders, Vitamin deficiencies (B12), Trauma, Brain tumors, Overuse of NSAIDS, Unhealthy diet, etc.

Common symptoms of Memory loss include:

• Memory loss
• Repeating conversations or questions
• Difficulty with communication/problems with language (verbal and written)
• Difficulty with complex tasks such as money management
• Misplacing items
• Unable to retain newly learned material
• Difficulty with planning and/or problem solving
• Confusion / Disorientation
• Paranoia / Changes in personality or mood
• Wandering/getting lost
• Taking longer to complete well known duties

Of all the factors potentially contributing to the development of memory loss particularly Alzheimer’s disease without disregarding the others, perhaps the three more important are: 

• Age 
• Family history 
• Genetics

All 3 are closely related. There are 4 known genes that have been linked to older patients with a family history of Alzheimer’s disease: APO-E4, Amyloid Precursor Protein (APP), Presenilin 1 (PSEN1) and Presenilin 2 (PSEN2). The best known and better understood however is the APO-E4 gene. 

In addition, there is considerable evidence that accumulation of the Amyloid and Tau protein in the Brain, Which are related to Chromosome 21, are implicated in memory loss and the development of Alzheimer’s disease. See the section on Down Syndrome and Alzheimer’s for more information.