Nursing care plans for Dementia, Dementia is a chronic disturbance involving multiple cognitive deficits, including memory impairment. Dementia is characterized by chronicity and deterioration of selective mental functions. Onset is insidious over months to years in most cases. Dementia is usually progressive, more common in the elderly, and rarely reversible even if underlying disease can be corrected. Dementia can be classified as cortical or subcortical.