In frontotemporal dementia, portions of the brain that lie behind the forehead and ears shrink, resulting in dramatic personality changes, socially inappropriate or impulsive behavior and emotional indifference. Movement and memory problems typically develop later in the course of the disease. According to the Mayo Clinic, frontotemporal dementia often begins between the ages of 40 and 65 and may be misdiagnosed as a psychiatric problem.
Lewy body disease is another cause of dementia in younger adults. It is associated with abnormal deposits of a protein called alpha-synuclein in the brain that affects brain chemistry and leads to behavioral, thought and movement problems. Most of the symptoms are similar to those seen in other dementias, and additional symptoms like hallucinations may resemble schizophrenia, but the decline in brain function occurs significantly faster. A distinguishing symptom of Lewy body dementia is having violent dreams and attempting to act them out, Dr. Knopman said.
Alzheimer’s disease remains the most common cause of dementia in younger as well as older adults. There is an inherited form of Alzheimer’s that typically arises at younger ages, but those cases account for fewer than 10 percent of young-onset disease. Most cases of Alzheimer’s occur sporadically, for unknown reasons, though genetic factors may increase risk.
People with Alzheimer’s typically have a buildup of abnormal substances — tau and beta-amyloid proteins — in the brain. Early symptoms include impaired memory, language problems, difficulty concentrating and finishing tasks, poor judgment and visual or spatial deficits that result in problems like driving errors and getting lost. Brain scans may show a loss of brain cells and an impaired ability to metabolize glucose that is indicative of degenerative brain disease.
Probably the most publicized factor known to increase the risk of early dementia is repeated head injuries like those experienced by professional boxers, football and soccer players, and sometimes by military veterans.
Once brain cells are injured or lost, there’s no going back. So preventing head injuries is the best possible protection at the moment.
Many parents these days try to discourage youngsters from playing sports like football, in which repeated head injuries are common. However, proper and consistent use of helmets and not heading the ball in soccer can limit their risk of head injuries. Dr. Knopman said he’s less concerned with elementary school children playing such sports; the risk of developing dementia at a young age from repeated head trauma is much greater among those who played Division 1 football or became professional boxers.