"Dementia" is a general term that refers to decline in multiple areas of thinking and/or memory while an individual is awake and alert; the decline is enough to interfere with normal daily functioning, whether on the job or at home.
The term "young-onset dementia" refers to dementia that begins before the age of 65, sometimes as early as the 30s and 40s. This is to be differentiated from "early stage dementia," which has nothing to do with age. Rather, it refers to the beginning of a dementia syndrome regardless of the age at which it starts.
Young-onset dementia can be caused by frontotemporal lobar degeneration (FTLD), Alzheimer's disease (AD), cerebrovascular conditions (e.g., multi-infarct disease, stroke), Parkinson's disease, Huntington's disease, prion diseases (e.g., Creutzfeldt-Jakob disease), and other conditions.
These early dementias are devastating neurological conditions that exact a tremendous emotional and financial toll on patients and their families and present a host of challenges never envisioned by the young patients. The condition causes a unique problem not only because it is so unexpected but because most of the potentially helpful programs and services that a younger patient needs have all been carefully designed and targeted for much older people.
One of the major problems with young-onset dementia is that it cuts down a person in their prime wage-earning years. While most older people with dementia are retired, many people with young-onset dementia are still working when they are diagnosed.