People who say their lives have a purpose are less likely to develop Alzheimer's disease or its precursor, mild cognitive impairment, a new study suggests.
As the population ages and dementia becomes a more frequent diagnosis, there's increasing impetus to determine the causes of the disease, associated risk factors and how to prevent it, explained study coauthor Aron S. Buchman, MD, an associate professor in the department of neurological sciences at Rush University Medical Center in Chicago.
"There has been a lot of interest in psychosocial factors and their association with cognitive decline and dementia in later life," he said.
The study looked at the positive aspects of life and their possible effect on keeping dementia at bay, "looking at happiness, purposefulness in life, well-being and whether those kind of concepts are associated with a decreased risk of dementia," Dr. Buchman explained.
For the study, published in the Archives of General Psychiatry, Dr. Buchman and his colleagues collected data on 951 older people without dementia who participated in the Rush Memory and Aging Project. The participants were asked to respond to statements such as: "I feel good when I think of what I have done in the past and what I hope to do in the future," and "I have a sense of direction and purpose in life."
After an average four years of follow-up, 16.3% of the people in the study developed Alzheimer's disease. Taking into account other factors that could account for Alzheimer's, the researchers found that people who responded most positively to statements about their lives were the least likely to develop the condition. Also, people who said they had more purposeful lives were less likely to develop mild cognitive impairment and had a slower rate of cognitive decline.
People who scored 4.2 out of 5 on the purpose-in-life measure were about 2.4 times less likely to develop Alzheimer's disease compared with people who scored 3.0, the study found.
It's not known whether there is a biological reason for this finding, the researchers noted.
"One possibility is that truly, somebody with high purpose in life might have a lower risk of developing dementia because of what's involved in purpose in life," Dr. Buchman said.
"The importance of the study," he added, "is this doesn't prove anything, but it points researchers in the direction of a link between purpose in life and cognition in late life. And now we have to find out what the biological basis is."
Still, the researchers think these findings could have implications for public health.
"More social activity, more physical activity, higher cognitive activities, high purpose in life—all these psychosocial factors seem to be linked with longer life, decreased mortality, decreased disability and provide important clues to a public health approach to try to increase independence in older people in later life," Dr. Buchman said.
Greg M. Cole, PhD, a neuroscientist at the Greater Los Angeles VA Healthcare System, wondered if the study is really measuring depression, not a purposeful life.
"I am unclear about how low scores on the purpose-in-life measures can be separated from mild depression," Dr. Cole said. "Depression has been repeatedly associated with increased Alzheimer's disease risk. So psychiatrists can make a distinction, but they seem likely closely related.
"One wonders whether this is a treatable psychiatric condition contributing to risk or an early symptom of decline," he added.
William H. Thies, PhD, chief medical and scientific officer at the Alzheimer's Association, said the new study "contributes to the literature that says there is a linkage between behavior and disease."
The question is do more people lack a sense of purpose and develop Alzheimer's disease or is lacking a sense of purpose an early, subtle, sign of dementia, he said.
"As we get better and better at having biological measures of the disease, we will shed a lot of light on these kinds of studies and whether these behaviors are simply a symptom or they are a place where you can intervene," Dr. Thies said.