Are All Dementias the Same?
Alzheimer’s disease is the most common form of dementia. Approximately two out of every three cases of dementia is related to Alzheimer’s disease. Other common dementias include: vascular dementia (up to 20% of patients with dementia), dementia with Lewy bodies (approximately 15% of all dementia cases), and frontotemporal dementia (less than 5% of dementia cases).37 In many cases the diagnostic criteria for these dementias overlap and patients may present with symptoms for multiple forms of dementia.10 Further, dementia may be a comorbidity with other diseases.10 Finally, a small number of dementia cases are associated with less common underlying causes. These may include Parkinson’s Disease Dementia, Huntington’s Disease, Creutzfeldt-Jakob Disease and other Prion Diseases, Dementia in HIV/AIDS, Traumatic Brain Injury, and Wernicke-Korsakoff Syndrome, which includes dementia from alcohol abuse.38
Dementia generally does not have one distinct cause. It is well-established that dementias, especially the most common forms, have a variety of risk factors and that these risk factors may vary throughout life. Educational attainment in childhood and early adulthood, is protective against dementia, i.e., patients with higher levels of education demonstrated delayed dementia onset once they are of older age.39 Additionally, hypertension, type 2 diabetes mellitus, hyperlipidemia, decreased cognitive activity, social isolation, lack of exercise, alcohol use, dietary factors, and smoking have also been associated with dementia development.39,40 Late-onset Alzheimer’s is the most common form of dementia. This dementia is considered to be multifactorial with disease development due to genetic, lifestyle, and environmental factors. Several genes and genetic polymorphisms have been identified as playing a role in the development of Alzheimer’s Disease. Such genes may convey an increased risk through mechanisms that include: increasing the production of presenilin and b-amyloid precursor protein (BAPP) and enhancing the deposition of b-amyloid protein in brain tissue.41 In addition to these genetic risk factors, environmental/lifestyle factors may induce epigenetic alterations of the genome (modification of the genome to turn genes off), which could increase risk for dementia development in some patients.42 Lastly, destruction of the blood-brain barrier may result in increased permeability which can lead to introduction of neurotoxic substances, including bacteria and bacterial byproducts, into brain tissues which have the potential to contribute to neurodegenerative diseases.43