Alzheimer disease is the most common cause of dementia, responsible for 60-80% of all dementias. The prevalence is strongly linked to age, with >1% of 60-64-year-old patients being diagnosed with the condition, compared to 20-40% of those over 85-90 years of age.
Epidemiological risk factors have been identified, including:
- advanced age
- female gender
- apolipoprotein E (APOE) e4 allele carrier status
- current smoking
- a family history of dementia
- mutations of amyloid precursor protein
- Down syndrome
It should also be noted that in addition to the genetic and environmental factors above, the age of an individual's presentation will also be influenced by socio-economic factors such as:
- fewer years of formal education
- lower income
- lower occupational status
- smaller social network/family support
It is not so much that these factors are risk factors to the underlying pathology but rather that individuals with pre-morbid higher function/supports are able to compensate for early disease changes to a greater degree, and thus present later. This is supported by the fact that these high functioning individuals when they eventually present, tend to have more marked morphological changes.