CHICAGO: People who lead a good clean life - those who are conscientious, self-disciplined and scrupulous - appear to be less likely to develop Alzheimer's disease, US researchers said on Monday.

The finding is the latest from a long-running study of nearly 1,000 Catholic nuns, priests and brothers by Robert Wilson of Rush University Medical Center in Chicago. The study appeared in the Archives of General Psychiatry .

Wilson and colleagues defined conscientiousness in the study as people who control their impulses and are goal-directed. These people are often considered dependable. People in Wilson's study did not have dementia when the study started in 1994.

The researchers asked the volunteers to rank themselves on a five-point scale according to a 12-item inventory, with questions such as "I am a productive person who always gets the job done." From this, they derived a conscientiousness score, based on a scale of 0 to 48. The average score was 34.

They were also given various medical and neurological exams, including cognitive testing. Follow-up tests were done each year through 2006. A total of 176 people developed Alzheimer's disease during the study.

People who were highly conscientious - those in the 90th percentile with scores of 40 or higher, had an 89% lower risk of developing Alzheimer's disease than those who ranked in the 10th percentile.