High Conscientiousness Linked to Decreased Risk for AD

October 11, 2007 — Being conscientious — having the ability to control impulses and to be goal directed — may provide some protection against developing Alzheimer's disease (AD), according to a new study published in the October issue of the Archives of General Psychiatry.
The study suggests that conscientiousness may be a subtle early indicator of AD, a result that could pave the way for developing novel strategies to delay the symptoms of this disease, the study authors believe.
The study also linked conscientiousness with a lower risk for mild cognitive impairment, a condition that in many cases precedes the onset of AD. However, it did not find an association between conscientiousness and the hallmark signs of AD such as brain plaques.
"This is the first evidence that this trait of conscientiousness has anything to do with Alzheimer's disease," said Robert S. Wilson, PhD, professor of neuropsychology at Rush University in Chicago and lead author of the study. The essential feature of conscientiousness, he noted, is impulse control.
"People who are high on this trait are able to delay gratification; they're self-disciplined rather than impulsive," Dr. Wilson told Medscape Psychiatry. "They tend to be dutiful and reliable and they follow rules. There's also an achievement aspect to this; people high on this trait tend to be goal-directed and organized."
Cognitive Testing
For the study, researchers observed 997 older Catholic clergy (nuns, priests, and brothers) from 1994 until 2006. On enrollment, participants underwent a clinical evaluation that included cognitive testing. None of the participants had dementia when the study began.
Conscientiousness was measured at the beginning of the study with use of a 12-item inventory for which participants rated their agreement with various statements (eg, "I am a productive person who always gets the job done") on a scale of 1 to 5. Higher scores indicated more conscientiousness. Total scores for participants ranged from 11 to 47, with the average score being 34. Scores on conscientiousness were not related to age but were higher in women. The study also measured other personality traits including neuroticism, extraversion, agreeableness, and openness. Annual cognitive tests included measurements of episodic memory, semantic memory, working memory, and perceptual speed.
During the course of the 12-year study, 176 participants developed AD. Those whose scores on conscientiousness were 40 or higher had an 89% lower risk of developing AD than those whose scores were 28 or lower. Neuroticism — but not extraversion, openness, or agreeableness — was also associated with an increased risk for AD.
The link between conscientiousness and AD persisted even after controlling for several risk factors. "We controlled for how physically active, how socially active, how mentally active people were," says Dr. Wilson. In addition, they adjusted for apolipoprotein genetic status; depressive symptoms; and vascular factors, including smoking.
The finding that women were more likely to be conscientious does not conflict with the perception that women are at increased risk for AD because there is no clear evidence that this increased risk actually exists, says Dr. Wilson. "Prior to the age of 85, there's no really good evidence overall that women are at increased risk," he said.
Plaques and Tangles "Not the Whole Story"
During the study, 383 participants died. Brain autopsies on 324 of these participants showed that conscientiousness was not associated with protein plaques and tangles in the brain.
"It's not clear why conscientiousness is linked to AD but not to these hallmark AD lesions," says Dr. Wilson. Plaques and tangles are clearly "not the whole story. There is more than one way to develop dementia in old age, with underlying pathology being just one way."
"The correlation between those pathological lesions and whether or not you develop dementia is far from perfect," he added. Indeed, "many people die with enough plaques and tangles to qualify for the pathologic diagnosis of AD and yet they had no or very few cognitive problems before they died." Something else seems to be determining how vulnerable a person is to these brain lesions, said Dr. Wilson. "Some other factors may increase the likelihood that those plaques and tangles, when they develop, will lead to dementia."
Just how might being conscientious, also described as being purposeful or having a will, alter risks for AD? Conscientiousness may increase the chances of higher academic and occupational achievement, both of which are proved to lower the risks for AD, the study authors note. As well, conscientiousness has been linked with resilience and with the ability to cope with difficulties. These characteristics might lessen the consequences of difficult life events and chronic stress, which have also been linked to dementia in old age, the study authors write.
The National Institute on Aging supported this research. The study authors have disclosed no relevant financial relationships.
Arch Gen Psychiatry. 2007;64:1204-1212.