Patients who maintain a greater sense of purpose in life as they age may have greater protection against Alzheimer's disease, researchers have found.
Those with a purpose had more than a 50 percent reduced risk of the disease, Dr. Patricia A. Boyle of Rush University Medical Center in Chicago and colleagues reported in the March issue of the journal Archives of General Psychiatry.
"The tendency to derive meaning from life's experiences and to possess a sense of intentionality and goal directedness are associated with a substantially reduced risk of Alzheimer's disease and a less rapid rate of cognitive decline in older age," the researchers wrote.
Some data have suggested that psychological factors such as extraversion and neuroticism, as well as experiential factors including social networks, are associated with risk of Alzheimer's disease.
Purpose -- which the researchers define as a "psychological tendency to derive meaning from life's experiences and to possess a sense of intentionality and goal directedness that guides behavior" -- has long been thought to protect against adverse health outcomes. For example, it was recently reported to be associated with longevity, they noted.
But there was little information on the association of purpose with Alzheimer's disease.
So the researchers conducted a study of 951 community-dwelling older patients without dementia who participated in the Rush Memory and Aging Project.
Each had a baseline evaluation about purpose in life, which incorporated a 10-item scale that included agree/don't-agree 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 enjoy making plans for the future and working them to a reality."
Patients were followed for up to seven years, with an average follow-up of about four years. During that time, 155 patients developed Alzheimer's disease.
The researchers found that those who developed the disease were older and reported lower purpose in life than those who did not.
Greater purpose in life was associated with a 52 percent reduced risk of Alzheimer's, and those with a high score on the purpose-in-life measurement were 2.4 times more likely to remain disease-free than low-scorers.
The association persisted after controlling for several factors, including depressive symptoms, neuroticism, social network size, and number of chronic medical conditions, the researchers found.
Similarly, those who developed mild cognitive impairment (MCI) were older and reported lower purpose in life scores than those who were not impaired. They also had a higher number of depressive symptoms.
There were other benefits as well. Having a greater sense of purpose was associated with reduced heart attack risk of almost 30 percent, as well as a 1.5-fold increased likelihood of remaining heart attack-free, compared to low scorers.
Researchers aren't sure of the biological mechanisms involved in the association, but other studies have found sense of purpose to be associated with lower levels of immune markers, including the stress hormone cortisol and inflammatory hormones.
Sense of purpose also has been positively associated with high-density lipoprotein -- the type of cholesterol known as HDL or "good" cholesterol. Additionally, it has been negatively correlated with waist-hip ratios -- in other words, high-purpose people look slimmer.