Complex and Alarming Links Between Chronic Pain and Dementia 2023

Chronic pain is known to be associated with dementia, and many studies have explored the connection. For example, a large study published in 2021 looked at data from 9,000 patients, going back in some cases as long as 27 years. The researchers found that people with dementia reported slightly more chronic pain as long as 16 years before the dementia diagnosis, as well as increasing pain intensity over the years, as compared to people who did not develop dementia.¹

Complicating the experience of pain in individuals with dementia is their frequent inability to express that pain and get relief, added Jennifer Winegarden, DO, MS, senior associate consultant in palliative medicine at Mayo Clinic Health System in Wisconsin, who has written about dementia-related pain. The usual manifestations are not there, she said. “You won’t always see a lot in the face [to suggest pain].” For those who claim pain is a result of inactivity, Dr. Winegarden said that is not true. “It boils down to neuroinflammation. Physicians have to be aware this exists, it’s part of the process and you are going to see a pathologic overlap [between the two conditions].”

More Pain Sites, Greater Dementia Risk

“Multisite chronic pain may lead to up to 8 years of accelerated hippocampal aging, an effect that may underlie a series of cognitive burdens,” explained Dr. Tu.

For the longitudinal, cross-sectional study, Dr. Tu and colleagues analyzed data from 354,943 patients, ages 39 to 82 years old, in the UK Biobank cohort to determine which participants developed dementia. MRI data and cognitive testing from a subset of participants were also analyzed.³

The team found that patients with multisite chronic pain had a significantly increased risk of dementia, more rapid cognitive decline, and greater hippocampal atrophy than did patients with no pain and patients with single-site chronic pain. The detrimental effects of multisite chronic pain on dementia risk and hippocampal volume were found to be worse as the number of chronic pain sites increased.

The effect on hippocampal volume was marked as well. For example, single site chronic pain was associated with a 9.795 mm³ reduction in the volume in the left hippocampus and 8.272 mm³ in the right. When the pain was in three sites, the reduction was 33.255 mm³ in the left and 36.042 mm³ in the right. For five sites or more, the reduction was 100.330 mm³ in the left and 87.522mm³ on the right.

Still More Questions

“Unfortunately, pain is a part of aging,” Dr. Kaye said, pointing out that some studies have suggested that 70% to 75% of the elderly population may have chronic pain. This study adds to the weight of evidence that pain is a common complaint for dementia patients, he said, but more work needs to be done to determine how specific it is to dementia. The research, he noted, did not focus on the mechanism of how chronic pain might lead to hippocampal volume loss. Nor did the researchers examine the causes of the chronic pain. For example, inflammation can cause pain, and inflammation has been implicated in the pathophysiology of Alzheimer’s disease.

For Dr. Winegarden, this means that it’s always crucial to consider pain in adults with dementia. “Keep a very high index of suspicion that a person with moderate to severe dementia has a pain they cannot communicate.” Clinicians, she said, as well as families, often overlook the probability of pain. “This is a very, very serious issue,” she said. “We are talking about 5 to 6 million, just in the US [with dementia]. Chronic pain can worsen their cognitive, functional, and emotional behaviors.” She also advises clinicians (and family members) to monitor the effect of any pain medication being used as it can lose effectiveness over time.

Added Dr. Kaye, the increased risk of dementia in those with chronic pain is yet another reason to effectively treat pain, said Dr. Kaye. Although he noted the many challenges to treating chronic pain, particularly in the elderly. “There’s still a lot of work to do on the mechanistic links [between pain and dementia] as well as on the practical part of treating chronic pain.”