3. Vascular dementia
Vascular dementia is the second most common type of dementia. There are no known single-gene mutations for the more common forms of vascular dementia but researchers are looking for multi-gene variants or 'risk genes' for the condition.
Familial vascular dementia
Some very rare forms of vascular dementia are caused by gene mutations. Mutations in a gene called NOTCH3 cause a rare form of vascular dementia known as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). CADASIL is inherited in a simple, single-gene pattern like familial Alzheimer's disease.
Risk genes for vascular dementia
Some studies have reported links between APOE (which plays a role in Alzheimer's disease - see above) and vascular dementia, but others have not. It seems that APOE e4 may be a risk factor for vascular dementia, but a weaker one than it is for Alzheimer's disease. It is not clear whether APOE e2 is associated with lower risk of vascular dementia as it is with Alzheimer's.
In addition, researchers have found several genes that affect a person's chances of developing conditions such as high cholesterol, high blood pressure and type 2 diabetes. These conditions matter because they can significantly raise a person's chances of developing vascular dementia later in life. Similarly, a family history of stroke or heart disease - both closely linked to vascular dementia - can raise a person's risk of developing it.
Overall, however, genes seem to play a much smaller role in the development of the common forms of vascular dementia than they do in late-onset Alzheimer's disease. Lifestyle choices (eg diet and exercise) are probably even more important in vascular dementia risk than they are in Alzheimer's disease.