Professor of psychiatry at the University of Gothenburg, Dr. Ingmar Skoog, and colleagues conducted a study which showed that women with certain personality traits at middle age were twice as likely to develop Alzheimer's 40 years later.
The study involved 800 women between the ages of 38 and 54 (in the year of 1968), in which the women filled out personality questionnaires and their cognitive skills were periodically evaluated. The personality spectrum ranged from neuroticism—women who reacted more emotionally to events, worried more, and had lower self-esteem—and extraversion—women who showed higher levels of trust and fewer emotional imbalances.
Four follow-ups in the study were made over the next 38 years, at which the women reported their stress levels. Women who had higher neuroticism scores also had higher stress levels, and vice versa for women who had lower neuroticism scores.
Dr. Skoog believes that stress may be the primary correlation between personality and the chance of developing Alzheimer's later in life, and that characteristics of neuroticism are very intertwined with high stress levels. Prior studies have also supported that higher stress levels can lead to dementia.
Although Skoog doesn't believe that altering one's stress patterns or negative emotions can entirely prevent Alzheimer's or dementia, he says that the connection is a productive one: “It’s important to try to find as many factors as you can that contribute to common disorders. The more factors we can do something about, the more we can reduce risk quite substantially.”