Chronic pain affects a quarter to a third of older adults and your risk rises with age.
While those medical facts may not surprise you, this one might: Chronic pain occurs even more frequently in patients with neurodegenerative disorders such as Alzheimer’s disease.
Why is this?
Researchers have a theory or two and, recently, decided to put them to the test. Here’s the story…
A number of studies have linked pain or painful chronic conditions such as osteoarthritis with cognitive decline and dementia. In fact, a review of ten studies published in 2016 found that half of dementia patients complained of pain.
The first study to demonstrate that older people with persistent pain experience faster declines in memory, and are more likely to develop dementia, was published in JAMA Internal Medicine in 2017.
Memory Declines Faster with Pain
Researchers at the University of California, San Francisco, analyzed data from 10,065 participants aged 60 and over who answered questions regarding pain and cognition in both 1998 and 2000. At these times 10.9 percent were affected by persistent pain.
After 12 years of follow up, those reporting moderate to severe pain in both interviews declined cognitively 9.2 percent faster in tests of memory function compared to those untroubled by pain.
In addition, those suffering from chronic pain also had a small but significant increase in the likelihood of developing dementia.
Is Pain Damaging Memory?
Pain might affect the brain in a way that also impacts cognitive processes. The researchers suggested pain could directly affect cognition possibly by compromising the brain’s ability to encode memories and other cognitive functions. Or the effect of cognitive decline on one or more brain regions might also bring on pain. Then again it might not be pain itself that causes cognitive changes, but the painkillers sufferers use. Another possibility arises from the emotional stress of being in pain. This activates stress-hormone pathways that have been implicated in cognitive decline. The researchers conceded that it could also be some other factor not accounted for in the study.
The first study to examine the link between pain and dementia over a much longer time frame was published in the journal Pain in May.
The new study was led by researchers at Université de Paris. They used data from the long running Whitehall II study of British civil servants. Participants were aged between 35 and 55 when they enrolled and took part in multiple surveys over 27 years.
Out of 9,046 participants, 567 developed dementia. Those diagnosed with the condition reported slightly more pain as early as 16 years before their diagnosis and significantly more pain at the time of diagnosis than those who remained dementia free.
The researchers don’t believe pain either caused dementia or increased the risk because the brain changes linked to dementia start decades beforehand. Instead, they suggest chronic pain might be an early symptom of dementia or simply correlated with dementia.
Scientists from China looked at the effect of widespread pain and its link to dementia, Alzheimer’s and stroke.
47 Percent More Likely to Have Alzheimer’s
The Chinese team drew on data from 2,464 Americans. Of these, 14 percent suffered widespread musculoskeletal pain – pain above and below the waist, on both sides of the body, the skull, backbone and ribs – while the remainder had either some joint pain or none. All were cognitively healthy when the study began.
The researchers took into account a very wide range of factors that could influence the results, such as age, general health, and lifestyle.
The findings, published in the journal Regional Anesthesia & Pain Medicine in August, found that after ten years of continuous monitoring, compared to those without widespread pain, those with pain were 47 percent more likely to have Alzheimer’s, 43 percent more likely to be diagnosed with any type of dementia, and they were also 29 percent more likely to have a stroke.
The researchers speculated that chronic pain could have a negative impact on lifestyle factors such as exercise or diet and that could increase the risk of these diseases. They also suggested that pain, and the stress it causes, might compete for resources in the brain that also deal with cognition. A third possibility is that pain could be an early indicator of dementia and Alzheimer’s.
This study, like the previous ones, is observational, so it’s not possible to determine cause and effect, but these studies do confirm a clear relationship between chronic pain and dementia. It will take a good deal of rigorous clinical work to determine what causes what and why.
As the research continues I’ll keep you updated. And I’d be surprised if they don’t find chronic inflammation as the thread tying together pain and Alzheimer’s disease. A number of studies we’ve reported on here over the years point to inflammation’s role in brain deterioration and memory loss. And of course, we all know that inflammation also plays a big role in most cases of chronic pain.