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Study claims Alzheimer's risk is linked to attitude

Tuesday 2 October 2007

“Being conscientious in life halves your risk of developing Alzheimer's disease” The Daily Mail reported scientists as saying. According to the paper, a study in “hundreds of nuns, monks and priests” over the age of 65, found that those who were judged to be productive, dependable or reliable were less likely to be affected by the degenerative disease. The article concludes that further research could lead to treatments for Alzheimer’s disease.

These reports are based on a 12-year study of almost 1,000 older Catholic nuns and priests in the US. Although this is a very interesting study, and was well designed and conducted, it is not possible to draw firm conclusions about the relationship between conscientiousness and risk of Alzheimer’s disease.

Alzheimer's is a slowly progressive disease that appears to be capable of affecting almost anyone and it is possible that people in the study had begun developing it without showing any signs or symptoms. Indeed, autopsies on those who died during the study found that more conscientious people were as likely to show the physical signs of dementia or Alzheimer’s as the less conscientious.

This study does not show that changing your habits to become more conscientious would reduce your risk of Alzheimer’s disease.

Where did the story come from?

Doctors Robert Wilson, David Bennett and colleagues from the Rush Alzheimer’s Disease Center and affiliated centres carried out this research. The study was funded by the US National Institute on Aging. The study was published in the peer-reviewed medical journal: The Archives of General Psychiatry.

What kind of scientific study was this?

This study reported results from a prospective cohort study called the Religious Orders Study.

Researchers enrolled 997 elderly Catholic nuns, priests, and brothers who were on average about 75 years old. According to accepted diagnostic criteria, none of the participants had dementia when they were enrolled. All the participants had a clinical evaluation, including cognitive testing, a neurological examination. They also completed a one-off questionnaire to assess how conscientious they were (higher scores indicated more conscientiousness).

The people who took part were annually assessed for Alzheimer’s disease and cognitive ability. Participants were followed for up to 12 years, with an average of about eight years. If participants died, their brains were examined to see if they had the typical physical signs of Alzheimer’s disease or other causes of dementia.

Researchers then used statistical analyses to look at whether conscientiousness affected how likely a person was to develop Alzheimer’s disease, mild cognitive impairment or to have worsening cognitive ability. These analyses took into account factors that might affect risk of Alzheimer’s, including age, gender, education, personality traits, genetic risk factors, medical risk factors and conditions such as diabetes and stroke, and cognitive and physical activity level.

What were the results of the study?

About 18% of participants (176 people) developed Alzheimer’s disease. People who had been evaluated as the most conscientious (scoring in the top 10%) were less likely to be diagnosed with Alzheimer’s disease than people who were the least conscientious (scoring in the bottom 10%).

People who were the most conscientious were also less likely to have mild cognitive impairment, and had less of a decline in their cognitive function than people who were the least conscientious.

However, autopsies on people who had died revealed that more conscientious people were just as likely to show the physical signs of dementia or Alzheimer’s disease as those who were less conscientious.

What interpretations did the researchers draw from these results?

The researchers concluded that a person’s “level of conscientiousness is a risk factor for Alzheimer’s disease”.

What does the NHS Knowledge Service make of this study?

This study was well designed and conducted. However, the relationship between the brain and our personality is a complex one that is not yet fully understood. Based on the results of this study, it would be very difficult to say that being conscientious actually prevents Alzheimer’s disease for a number of reasons.

  • Alzheimer’s is a slowly progressive disease, and it would be difficult to pinpoint the exact point when it started to develop. It is possible that although the participants did not seem to have dementia when they enrolled, the insidious process of changes in the neurons in the brain that are part of Alzheimer’s disease may already have started. If this were true, a lack of conscientiousness could be a result of early Alzheimer’s, rather than a potential cause. The authors of the study thought this to be unlikely, and pointed out that people with varying levels of conscientiousness had similar cognitive function when they were enrolled.
  • A clinical diagnosis of Alzheimer’s disease is usually made when any other psychiatric or medical cause of the signs and symptoms have been excluded. These include impaired memory, problems with facial recognition and language and difficulty performing daily tasks. The disease is also gradual in onset. Although this study reports that the diagnosis was based on clinical criteria, it is not clear whether any of these people had radiological exams while they were alive which could have identified another potential cause of the signs and symptoms, e.g. vascular dementia from a stroke.
  • A definitive diagnosis of Alzheimer’s is based upon these clinical features in addition to the results of an autopsy. It is therefore important to note that the study found that conscientiousness was not associated with Alzheimer’s in the participants who had an autopsy.
  • Rather than indicating that people do not develop Alzheimer's because they are more conscientious, it is entirely possible that they have other characteristics which could cause them to be both more conscientious and also less likely to develop Alzheimer’s disease.
  • This study included a very select group of people, who are not representative of the general population in terms of lifestyle and education. Therefore, these results cannot be extrapolated to the population as a whole.

In light of these points, it is too early to suggest that conscientiousness may help to predict a person’s likelihood of developing Alzheimer’s, or that not being conscientious is a “risk factor” for Alzheimer’s.

It is also important to note that this study is unable to say that if you change habits to become conscientious, it will reduce your risk of developing Alzheimer’s.

Sir Muir Gray adds...

Whether or not this relationship is one of cause and effect, and this has not yet been established, we have to ask what could be done if ‘not being conscientious’ were shown to increase the risk of Alzheimer’s. I cannot think of anything that an individual, or the NHS, could do.

Analysis by Bazian
Edited by NHS Website

Links to the headlines

Why a dose of self-discipline could help ward off Alzheimer's.

Daily Mail, 2 October 2007

Alzheimer's linked to behaviour study suggests.

The Telegraph, 2 October 2007

Links to the science

Wilson RS, Schneider JA, Arnold SE, et al.

Conscientiousness and the Incidence of Alzheimer Disease and Mild Cognitive Impairment.

Arch Gen Psychiatry 2007; 64:1204-1212.