Conscientiousness and Alzheimer's disease

Individuals who are more conscientious - in other words, those with a tendency to be self-disciplined, scrupulous and purposeful - appear less likely to develop Alzheimer's disease, according to a report in the October issue of Archives of General Psychiatry.

Conscientiousness refers to a person's tendency to control impulses and be goal-directed, and is also known as will, work and dependability, according to background information in the article. It has been associated with a wide range of mental and physical disorders, disability and death, suggesting it may be important for maintaining overall health.

Robert S. Wilson, Ph.D., of Rush University Medical Center, Chicago, and colleagues studied 997 older Catholic nuns, priests and brothers who did not have dementia when the study began in 1994. Participants underwent evaluations that included medical history, neurologic examinations and cognitive testing. Conscientiousness was measured with a 12-item inventory, where participants rated agreement with each item (for example, “I am a productive person who always gets the job done”) on a scale of one to five. Scores ranged from zero to 48, with higher scores indicating more conscientiousness. The researchers conducted follow-up examinations annually through 2006, with an average of 7.9 evaluations per person.

The participants had an average conscientiousness score of 34 out of 48. Through a maximum of 12 years of follow-up, 176 individuals developed Alzheimer's disease. Those who had conscientiousness scores in the 90th percentile (40 points) or higher had an 89 percent lower risk of developing Alzheimer's disease than those whose scores ranked in the 10th percentile (28 points) or lower. Controlling for known Alzheimer's disease risk factors did not substantially change these results. Conscientiousness also was associated with a slower rate of cognitive decline and a lower risk of mild cognitive impairment, a condition that may precede Alzheimer's disease.

The researchers also analyzed results from brain autopsies of 324 participants who died during the study. In these patients, conscientiousness was not linked to any of the hallmark signs of Alzheimer's disease, including brain plaques and tangles. However, conscientiousness did appear to modify the association of these brain changes with an individual's cognitive abilities before death.

There are several ways by which conscientiousness might protect against Alzheimer's disease, the authors write. First, conscientious individuals may be more likely to experience educational or occupational success, both of which have been associated with a reduced risk of Alzheimer's disease. In addition, conscientiousness has been linked to resilience and to coping actively with difficulties. “These factors might lessen the adverse consequences of negative life events and chronic psychological distress, which have been associated with risk of dementia in old age,” the authors note.

“In conclusion, level of conscientiousness is associated with incidence of mild cognitive impairment and Alzheimer's disease but not with the pathologic hallmarks of these conditions,” they continue. “Understanding the mechanisms linking conscientiousness to maintenance of cognition in old age may suggest novel strategies for delaying the symptoms of Alzheimer's disease.”