By Dr. Lynn Webster, PNN Columnist
In 2017, JAMA Internal Medicine published a study that found older people with chronic pain experience faster declines in memory and are more likely to develop dementia. While prior research had shown a link between chronic pain and brain damage, this was one of the first studies to specifically suggest that chronic pain can cause dementia.
The authors reported that people aged 60 and over with persistent pain experienced a 9.2% more rapid decline in memory score when compared to people of the same age without chronic pain. This means that people with chronic pain may experience more difficulty in managing their finances, medications and social connections.
Dementia is a chronic condition of the brain that involves memory, personality and judgment. It is not a disease; it is a symptom of one or more diseases.
There are many types of dementia. Alzheimer’s disease is considered to be the most common.
Dementia usually worsens over time if the underlying disease remains static or progresses, as is the case with many chronic pain conditions.
There are an estimated 20 million Americans with high impact (the most severe) chronic pain who may be experiencing accelerated decline in cognition due to their pain. The amount of dementia appears to be associated with the severity and duration of chronic pain. Undertreated or untreated chronic pain may accelerate dementia.
Chronic pain affects an even larger percentage of elderly adults (one in three) than the general population. Since the prevalence of chronic pain increases with age, the probability of experiencing dementia increases as well. However, the reasons for that go beyond aging itself.
Seniors are more likely to take multiple medications that can contribute to mental confusion. On average, elderly people take five or more prescriptions. They may also use over-the-counter medications, which adds to potential drug-associated mental compromise.
Opioids, in particular, have been implicated in cognitive impairment. However, a study published in 2016 suggests there is no difference in cognitive decline between people on opioids and those on nonsteroidal anti-inflammatory drugs. The study's implication is that pain, not opioids, leads to cognitive impairment.
Chronic pain appears to affect the function and structure of the hippocampus. This is the region of the brain that involves learning, memory, and emotional processing.
One explanation for the mental decline associated with chronic pain is that various areas of the brain compete for attention. Attentional impairment compromises memory by diverting attention to the areas of the brain processing pain. In effect, the brain is multi-tasking and favoring the processing of pain over cognition. This may, in part, explain the clinical phrase “brain fog.”
The Australian Broadcasting Company's "All in the Mind" website explains that pain damages the brain in several ways, including a change in the size of the thalamus and a decrease in the amount of a neurotransmitter (gamma-aminobutyric acid) the brain produces. In other words, chronic pain changes the brain structurally and functionally.
The prefrontal cortex is the part of the brain responsible for executive functions, such as cognition, social behavior, personality, and decision-making. It is also the part of the brain that modulates pain.
According to "All in the Mind," some researchers believe that chronic pain decreases the volume of the prefrontal cortex. Over time, brains damaged by pain lose the ability to handle pain — along with some of the personality attributes that make us who we are.
Brain Damage Can Be Reversed
The good news is that the brain damage caused by chronic pain can be reversed, at least to some extent. Unfortunately, the elderly are less likely to recover from dementia caused by chronic pain as compared with younger patients.
If pain is adequately treated, the brain may be able to regain its ability to function normally. A 2009 study of patients with chronic pain due to hip osteoarthritis showed reversal of brain changes when their pain was adequately treated.
People who don’t have their acute pain managed are more likely to develop chronic pain. It is postulated that the changes in the brain that occur with chronic pain begin with the onset of acute pain. There is also some evidence that an individual’s genes may influence who is at greatest risk for developing brain damage from chronic pain and who is least likely to recover from it.
Many people have criticized the concept of assessing pain as the 5th vital sign, and have called it a contributing factor for the opioid crisis. As I have said, pain may not be a vital sign, but it is vital that we assess it. Asking patients about their pain is critical to providing interventions that can mitigate the consequences of undertreated pain, including dementia.
Lynn R. Webster, MD, is a vice president of scientific affairs for PRA Health Sciences and consults with the pharmaceutical industry. He is author of the award-winning book, “The Painful Truth,” and co-producer of the documentary, “It Hurts Until You Die.” You can find him on Twitter: @LynnRWebsterMD.
The information in this column is for informational purposes only and represents the author’s opinions alone. It does not inherently express or reflect the views, opinions and/or positions of Pain News Network.