Etiologies and risk factors for dementia

Dementia is understood as a clinical syndrome characterized by impairment in memory impairment along with cognitive deficits in other domains. Over the years, understanding about the causes of dementias has improved. Broadly, dementias can be classified as irreversible degenerative dementias and reversible dementias. Alzheimer′s disease is the prototype of degenerative dementias and is characterized by the accumulation of beta-amyloid protein (called as amyloid plaques) outside the neurons and accumulation of tau protein (called tau tangles) inside the neurons. Vascular dementias are characterized by cerebrovascular insults which lead to pathological brain changes that impair cognition. The pathological hallmark of Lewy body dementia is the presence of α-synuclein neuronal inclusions, also known as Lewy bodies, accompanied by neuronal loss. Frontotemporal dementias are characterized by abnormal deposits of the microtubule-associated protein tau, the trans-activation response TAR DNA-binding protein with molecular weight 43 kDa (TDP-43), and the fused in sarcoma protein. Reversible dementias are characterized by the primary illness and may not present with characteristic brain deposits as seen with many degenerative dementias