Ongoing stress is blamed for contributing to an array of health problems - from depression to high blood pressure. Now researchers say it's also linked with a type of memory decline that's often a prelude to Alzheimer's disease.
In the new study of older adults, feeling stressed out increased the likelihood that people would go on to develop a form of mild cognitive impairment (MCI), according to scientists at Albert Einstein College of Medicine and Montefiore Health System. People with MCI face a greater risk of eventually developing Alzheimer's.
The researchers analyzed data from an ongoing study of adults age 70 and over from Bronx County, New York. All were dementia-free at the start of the study.
The participants were followed for an average of 3.6 years, and over the course of the study, 71 of the 507 were diagnosed with amnesiac mild cognitive impairment (aMCI), the most common form of the condition.
The greater a participant's stress level - which was measured using standardized stress tests - the greater their risk for developing cognitive impairment, the researchers reported. An MCI diagnosis was based on standardized clinical criteria including the results of memory recall tests and reports of forgetfulness from the participants or others.
High levels of stress were associated with a 30 percent greater risk of cognitive impairment, the authors reported in Alzheimer Disease & Associated Disorders.
"Our study provides strong evidence that perceived stress increases the likelihood that an older person will develop aMCI," said Dr. Richard Lipton, senior author of the study and vice chair of neurology at Einstein and Montefiore, in a press statement.
Keith Fargo, the Director of Scientific Programs and Outreach at the Alzheimer's Association, said it's important to note that the study did not look at Alzheimer's disease dementia.
"Instead, the authors measured new cases of amnestic mild cognitive impairment (aMCI), a condition characterized by a decline in memory that is measurable and noticeable but not severe enough to disrupt basic activities of daily living. In many people, aMCI appears to lead up to dementia, but in other people aMCI remains stable or even reverts to normal cognition," Fargo said.
A few other studies have measured stress and risk for aMCI and found results that are similar to this new research, Fargo said.
"According to the scientific literature, there appears to be some kind of connection between high levels of stress and later developing dementia due to Alzheimer's disease," said Fargo. But he explained that it is not yet clear whether the stress causes Alzheimer's, whether the decline into Alzheimer's disease is what causes the high levels of stress, or if both issues are involved.
Fargo said, "This observational study can only tell us whether there is an association between stress and later being diagnosed with aMCI. It cannot tell us whether stress or perceived stress cause aMCI."
Because stress is treatable, the authors said the results suggest that detecting and treating stress in older people might help delay or even prevent the onset of MCI and perhaps Alzheimer's.
"Fortunately, perceived stress is a modifiable risk factor for cognitive impairment, making it a potential target for treatment," Lipton said. "Stress management techniques ... could include physical activity, meditation, yoga."
Fargo said more research is needed to determine whether interventions aimed at modifying stress can delay or potentially even prevent cognitive decline. But because high stress can lead to a host of health problems, it's important people learn to manage it.
"In people with Alzheimer's dementia and their caregivers, symptoms such as anxiety and depression can be particularly debilitating, so stress management may be even more important for them and their caregivers," Fargo said.
He noted that there is strong evidence showing regular physical activity and management of cardiovascular risk factors - especially diabetes, obesity, smoking and high blood pressure - can reduce the risk of cognitive decline as people age and may also reduce the risk of dementia.
"Given that physical activity can have beneficial effects on stress levels and also helps control cardiovascular risk factors, keeping an eye on stress levels is likely to be beneficial to our cognitive health as we age," Fargo said.