Researchers at the University of California, San Francisco, have found that older people with persistent pain show quicker declines in memory as they age and are more likely to have dementia years later.
Published this week in JAMA Internal Medicine, findings from their study, which appears to be the first to make this association, indicate that chronic pain could somehow be related to changes in the brain that contribute to dementia.
The researchers analyzed data from 10,000 participants aged 60 and up over a 12-year period.
The participants who said they were persistently troubled by moderate or severe pain in both years 1998 and 2000 declined 9.2 percent faster in tests of memory function over the next 10 years than those who said they were not troubled by pain.
Those who complained about persistent pain also had a small but significantly increased likelihood of developing dementia overall.
Elizabeth Whitlock, a postdoctoral fellow in the UCSF Department of Anesthesia and Perioperative Care and the first author of the study, said the findings point toward new ways of thinking about how to protect older people from the cognitive insults of aging.
"Elderly people need to maintain their cognition to stay independent," she said. "Up to one in three older people suffer from chronic pain, so understanding the relationship between pain and cognitive decline is an important first step toward finding ways to help this population."
The research suggests three potentially overlapping reasons for the association between chronic pain and dementia: an increased dementia risk could be caused by painkillers, such as opioids; it could be that the experience of pain somehow compromises the brain's ability to encode memories and other cognitive functions; finally, it could be due to some other factor that was not measured in the study.
But even if this is the case, Whitlock said, the findings remain clinically relevant, because pain could be used as a marker for increased risk of future cognitive decline even if the biological basis of the association is still unclear.
People who suffer from chronic pain tend to have diminished attentional capacity and impaired memory, particularly when pain is severe or causes patients to ruminate, as it could divert enough attention to interfere with the consolidation of memory.
Another possibility, Whitlock was quoted as saying in a news release from UCSF, is that the emotional stress of being in pain activates stress-hormone pathways in the body that have been implicated in cognitive decline.
If either is the case, she noted, then effectively treating the pain could protect cognition.
Doctors often struggle to manage their patients' pain, since current therapies for patients in the United States, in addition to being addictive, do not always work.
However, Whitlock said that even those patients who continue to suffer, and may be experiencing a more rapid cognitive decline as a result, can still be helped with assistive devices, physical and occupational therapy, or strategies.