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Younger-onset dementia is any form of dementia that strikes people under the age of 65. Dementia sometimes occurs in people in their fifties, fourties, thirties, and even earlier in life.

Younger-onset (or young-onset) dementia is a group of conditions that cause loss of memory and cognitive abilities in adults who have not reached the age of 65. Younger-onset dementia may be caused by any of the same conditions that cause major neurocognitive impairment after the age of 65, including Alzheimer's disease, ​ frontotemporal dementia, Lewy body dementia, Huntington's disease, and prion disease. It can result from Huntington's disease, or it can be a later manifestation of dementias that usually strike before adulthood such as lysosomal storage disorders, leukodystrophies, and mitochondrial diseases. Sometimes younger-onset dementia is caused by reversible conditions such as normal pressure hydrocephalus, toxic exposure, infections, and sleep apnea. But whatever the cause, younger-onset dementia tends to be hard to diagnose.

About one out of every 1500 people aged 45 to 64 suffers some form of younger-onset dementia. In people who are still in mid-life, memory loss usually isn't the first symptom. There are more likely to be depression, loss of inhibition, and psychosis. Loss of memory and cognitive abilities only comes later in the disease. Alzheimer's is the most common cause of younger-onset dementia, but it occurs in only about 34 percent of cases, compared to 80 percent of cases of later-onset dementia (after age 65). Symptoms that suggest dementia rather than a psychiatric illness include:

  • Slow appearance of symptoms,
  • Lack of a precipitating event (such as a tragic loss or a major accident), but
  • Steady worsening of symptoms over time.
Doctors don't usually know to look for younger-onset dementia without the help of an informant who sees the patient every day. Most doctors are very hesitant to give a diagnosis of younger-onset dementia because of the wide-ranging and devastating effects of the disease on the patient's life.

Needs of people with younger-onset dementia

People who are diagnosed with younger-onset dementia often are still employed, or still trying to keep a job. They have car payments, mortgages, credit cards, and children who are still in school. They often are still physically strong and healthy, but the loss of income mzy may make bucket list plans for travel and time with grandchildren impossible. This frustration is compounded by the strain on family relationships and friendships. People who have younger-onset dementia usually don't look sick. They don't get sympathy for their condition. As the dementia progresses, it becomes more and more difficult for them to maintain social relationships, and they become progressively more isolated, which aggravates the symptoms of dementia.

Younger-onset dementia usually poses a huge challenge for the patient's partner. The partner or spouse may have to take on most or all of the responsibilities for raising children and also have to get an additional job, since disability benefits can be meager. Children of an adult who has younger-onset dementia chafe from the loss of material things and support for their own life plans, and may become resentful of their parent. They usually find it increasingly difficult to talk with their sick parent, and have to deal with their own depression and loss.

Fortunately, younger-onset dementia is sometimes reversible.

Reversible forms of younger-onset dementia

Any diagnosis of younger-onset dementia is devastating, but some forms of younger-onset dementia allow for hope. These forms of the disease allow for improvement, or at least periods of remission.

  • Multiple sclerosis. More common with women than with men, multiple sclerosis can cause episodes of dementia as early as age 20. These periods of months to years are usually marked by sensory loss in the arms and legs and disturbance of vision, such as double vision. Acute episodes are treated with steroids. Maintenance therapy usually involves drugs that reduce the activity of the immune system.
  • Autoimmune encephalitis. Caused by antibodies triggered by an infection, this form of younger-onset dementia can cause seizures and personality changes. Like multiple sclerosis, short-term treatment usually involves high-dose steroids and longer-term treatment requires immunomodulatory drugs. When the antibodies are formed in response to a tumor, usually it is necessary to remove the tumor.
  • HIV encephalopathy. This form of younger-onset dementia causes mood swings and a general slowing down of muscle movements. It is treated with HAART (highly active antiretroviral therapy).
  • Whipple's disease. This bacterial infection usually causes an inability to absorb nutrients from food. In about 10 to 40 percent of people who have it, the combination of malnutrition and the direct effects of the infection cause memory loss, confusion, and altered consciousness. This infection can be treated with antibiotics, but if it is left untreated, it becomes fatal.
  • Mercury poisoning. Toxic reactions to mercury are systemic, and usually involve redness and peeling of the skin, itching, burning, pain, mood swings, impaired memory, and insomnia. Mercury poisoning can be treated by medically directed chelation therapy with dimercaptosuccinic acid (DMSA, not to be confused with the DMSO used in natural medicine) or dimercaptopropane sulfonate (DMPS), but the longer treatment is delayed, the less likely it is to be successful.
  • Malnutrition. Not getting enough B vitamins can cause a treatable form of dementia known as Wernicke-Korsakoff syndrome. Deficiencies in other nutrients sometimes show up as anterograde amnesia (an inability to recall the immediate past while memories of the distant past are intact) and a tendency toward confabulation (distorted, fabricated, or misinterpreted memories about oneself or the world). Treatment requires replacing the nutrients that have become deficient.
It's important to exhaust all the possibilities for a reversible cause of younger-onset dementia before accepting a diagnosis of an irreversible, progressive form of dementia. Timely treatment sometimes restores mental function.

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  • Photo courtesy of SteadyHealth

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