Pernicious anemia is due to lack of vitamin B12, which causes progressive nerve damage, forgetfulness, loss of ability to concentrate and abnormal sensations such as burning, itching and loss of feeling. However, many people with pernicious anemia do not have abnormally low blood levels of vitamin B12.

A study in the Journal of the American Geriatrics Society shows that older people have lower blood levels of a chemical called homotranscobalamin II that carries vitamin B12 into the cells, so they need higher blood levels to have normal tissue levels.

Since low-normal blood level of vitamin B12 do not rule out B12 deficiency, the diagnosis of pernicious anemia is often made late in the course of the disease after many people have suffered permanent nerve damage. According to a report in the Archives of Internal Medicine, two percent of Americans over 60 have low blood levels of vitamin B12, but the incidence of vitamin B12 deficiency causing nerve damage in older people is much higher than that, sometimes as high as 50 percent. Therefore, many older people who are diagnosed with senility actually suffer from lack of vitamin B12 which can be cured by taking vitamin B supplements.

Lack of vitamin B12 also can cause heart attacks, so all people over 60 should be screened with blood tests for vitamin B12 and those with normal levels of B12 and symptoms of nerve damage or arteriosclerosis should also get a blood test called homocysteine.

Many people cannot correct their B12 deficiency with diet because they cannot absorb enough B12 from their food. Almost always, those with a deficiency can a cured by taking a 1000 microgram pill of vitamin B12 once a day. They usually do not need to take injections. Low levels of B12 are also associated with stomach diseases and infections such as Helicobacter pylori.