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Mounting evidence indicates that chronic exposure to emotional stressors, such as anxiety or fear, can make a person more susceptible to Alzheimer's disease. The latest study comes from a team at the Salk Institute for Biological Studies in San Diego that replicated the body's reaction to mild stress by physically restraining mice for half an hour. The incident modified the tau protein, which gives neurons structural support, rendering it unable to fulfill its role. “This conversion is a key event in the development of Alzheimer's,” says Robert A. Rissman, lead author of the study. After a single stress episode, tau morphed back into its original state within 90 minutes. When the team induced stress every day for two weeks, however, tau remained in its modified state long enough to allow the individual protein molecules to clump together. These protein heaps are the first step toward neurofibrillary tangles, one of the hallmarks associated with Alzheimer's.
Simply being prone to worry and tension can cause memory problems in old age, another recent study shows. Robert Wilson and his colleagues at Rush University Medical Center in Chicago evaluated the distress susceptibility of more than 1,000 elderly people by rating their agreement with statements such as “I am often tense and jittery.” Over a period of up to 12 years, volunteers who were anxiety-prone had a 40 percent higher risk of developing mild cognitive impairment than more easygoing individuals did. Mild cognitive impairment is thought to be a precursor for Alzheimer's.
Brain autopsies on participants who have died did not turn up evidence of neurofibrillary tangles or any of the other known features indicative of Alzheimer's, Wilson says. But he thinks it is possible that chronic distress gradually compromises memory systems, ultimately rendering a person more vulnerable to the physical changes in the brain associated with Alzheimer's.