More Pain, More Aging, and More Pain With Aging: Part 1
Editor’s note: This is Part 1 of PRF’s coverage of selected talks from a pre-conference workshop on pain and aging held at the 2017 International Association of Gerontology and Geriatrics (IAGG) World Congress. See Part 2 here.
In 2017, for the first time ever, the International Association of Gerontology and Geriatrics (IAGG) World Congress featured a pre-conference workshop on the topic of pain and aging. The workshop, titled “Pain and Aging: Measurement, Mechanisms, and Management,” and held July 23 in beautiful—and even sunny—San Francisco, US, featured many of the world’s leading experts on pain and aging. Eighty-six attendees from 24 countries gathered to listen to talks on pain epidemiology and assessment, biopsychosocial contributions to pain, pain and comorbidities, pain treatment, and incorporation of the social and behavioral sciences into pain research in elderly populations.
The event was led by workshop directors Roger Fillingim, University of Florida, Gainesville, US, and Cary Reid, Weill Cornell Medical College, New York, US. Sponsors included The Mayday Fund, the Translational Research Institute on Pain in Later Life (TRIPLL), Weill Cornell Medicine, the University of Florida Pain Research and Intervention Center of Excellence, the National Institute on Aging, Cornell University, the Bronfenbrenner Center for Translational Research, and the IASP Pain in Older Persons Special Interest Group.
Why hold a workshop on pain and aging? Fillingim noted during the event’s introduction that, on the one hand, chronic pain is an enormous public health challenge, affecting approximately 100 million people in the US alone at a cost of 0 billion dollars annually, according to a 2010 report from the Institute of Medicine. Chronic pain has a significant impact on function, too, with low back pain, for instance, being the leading cause of disability throughout the world. On the other hand, epidemiological studies show rapid growth in the elderly population, along with an increase in the prevalence of pain with age, though prevalence estimates do differ according to the specific pain condition under study. In short, the world is seeing more pain, more aging, and more pain with aging, making a workshop on pain in older adults timely and important.
Estimating pain prevalence: Variability is the name of the game
Stephen Gibson, Caulfield Pain Management and Research Centre, Caulfield, Australia, kicked off a session on pain epidemiology and assessment in older adults by pointing to the rapid aging of the world’s population that is expected over the next few decades. Because of improvements in public health, decreased mortality, and better management of chronic diseases, more than 30 percent of the world’s population will be in the cohort of elderly individuals by 2050. Startlingly, those living to 100 years or more are growing at a rate of 8 percent per year, and death rates in these centenarians have fallen by one-third in recent years.
In discussing the prevalence of pain throughout the lifespan, Gibson said that the underlying theme in this area of research is variability. Definitive figures are hard to come by, he stressed, considering the large range reported in the literature, and the wide range in prevalence within each age group. Nevertheless, it appears that pain prevalence increases throughout life, peaking at about 70 years of age and then plateauing or even declining. Still, pain affects about half of the older population, which is twice as many compared to younger adults.
To illustrate this variability, Gibson pointed to a literature review of studies in nursing home residents (Takai et al., 2010). The review included 27 studies with a total of more than two million residents. While the median prevalence of pain was 52 percent, estimates varied widely from less than 10 percent to more than 70 percent, likely because of differing research methods and data sources used in the studies, as well as the time frame over which pain was detected, among other factors.
Gibson also emphasized that the older population is not a single homogenous group. A 2014 study of healthy aging that looked at eight different older age groups, ranging from 51-54 all the way to 85 and older, found that many older individuals actually have good health and no health-based limitations in work or housework (Lowsky et al., 2014). This research showed that health must not be assumed to necessarily deteriorate with age. For instance, while a quality-of-life measure (incorporating mobility, self-care, activity, pain/discomfort, and anxiety/depression) did tend to worsen with age, there was nonetheless substantial variability within each age group, and only relatively small variation in median quality of life across groups.
Gibson then discussed the predictors of pain across the lifespan. Important predictors early in life include both genetics and environmental factors. For instance, in the latter case, a 2009 prospective study of childhood risk factors for later adult chronic widespread pain assessed at 45 years of age found that hospitalization following a traffic accident in childhood increased the risk of subsequent pain by 50 percent (Jones et al., 2009). Psychological factors, too, such as family difficulties and the death of one’s mother, were also significant predictors of future pain. Meanwhile, in later life, osteoarthritis is a particularly important risk factor, observable upon x-ray in the hands, knees, and feet increasing in prevalence with age.
But as yet another indication of the variability in pain prevalence, whether there is an increase in pain with aging depends on the type and location of pain. For example, Gibson said that while most locations show an increase in the prevalence of pain with age, especially the joints, legs, and feet, back pain is surprisingly different in this regard, with lifespan prevalence actually decreasing as people get older, as is the case for visceral pain. Complicating matters is that whether pain becomes more common with age also depends on the sex of study subjects, as well as the country in which they live (e.g., see Mansfield et al., 2016).
Further, all pain in the elderly is not equal regarding what these individuals need clinically to help with their pain. Here, Gibson said, the focus should be on pain that affects function. There are many ways in which pain can affect function in older individuals with pain, including the widespread prevalence (40-70 percent) of depression in this group, and an accompanying increased risk of suicide. Pain can also interfere with daily activities such as eating, dressing, going places, and doing housework, especially in those with cognitive impairment (Shega et al., 2010). Pain can also affect sleep, social relationships, finances, and cognitive performance. For instance, in the last case, pain in the elderly is associated with an increased risk of memory decline and dementia (Whitlock et al., 2017).
Nevertheless, Gibson emphasized that the literature on how pain with aging impacts function is sparse. Estimates from the limited data available suggest that about 10-20 percent of the elderly have pain severe enough to require clinical assistance, which is quite different from the overall 50 percent prevalence of pain in older people.
Gibson ended by noting a huge gap in the literature examining the prevalence of pain in the oldest old—and there isn’t a single study on those over 100 years of age. Considering how quickly this population is growing, more studies are needed in this area. Gibson’s message was clear: Don’t forget the centenarians!
Pain and depression—whom and how you measure
The relationship between pain and depression was the topic of a talk by Patricia Parmelee, University of Alabama, Tuscaloosa, US. She began by noting that depression is quite common in older people, who show a point prevalence of major depressive disorder of 3.3 percent, along with a lifetime risk of 16.5 percent, and a 19.5 percent point prevalence of less severe forms of depression (Volkert et al., 2013). Interestingly, though, and perhaps contrary to assumptions, major depression is not more common in later life, and in fact a loss of interest or pleasure in daily activities (anhedonia) is more common in older adults than depressed mood.
The relationship between pain and depression, however, is difficult to untangle because there are numerous symptoms of depression, including affective symptoms like poor mood and anhedonia, as well as vegetative symptoms like fatigue, sleep disturbances, and difficulty concentrating. Thus, Parmelee stressed, findings will depend on which specific symptoms and individuals are the focus of any particular study. With that caveat in mind, she noted the substantial comorbidity of late-life pain and depression. For instance, some studies show that 20-30 percent of older adults with chronic pain also exhibit symptoms of depression.
In terms of the direction of the relationship, Parmelee said that it goes both ways: Pain leads to depression, and depression to pain. That pain and depression track together could be due, in part, to shared neurobiological mechanisms, with many of the same brain structures implicated in each condition, as well as shared biochemical mechanisms. This could be why, Parmelee said, treating pain with antidepressants is effective. Pain is also a stressor, and pain and depression also share cognitive-behavioral linkages; catastrophizing can be a feature of both, for instance.
Parmelee then delved more deeply into the complexity of the association between pain and depression. Here she discussed two studies, one exploratory and one confirmatory, that she performed with colleagues. In the exploratory study (Parmelee et al., 1998), the researchers looked at 1,245 elderly long-term care residents, using factor analysis to identify three clusters of symptoms including depressed mood (DM), somatic symptoms (SS), and psychic anxiety (PA). Results showed that all three clusters were associated cross-sectionally with pain.
The confirmatory investigation (Parmelee et al., 2013) considered 367 older adults with knee osteoarthritis. Here, DM and SS were associated cross-sectionally with pain, but PA was not. But, for both studies, longitudinal findings showed no associations at all with pain. One key take-home message from these investigations, Parmelee said, is that pain-depression linkages are real, rather than solely the result of diagnostic confounding that can occur when looking at somatic symptoms such as fatigue or loss of appetite, which feature in many different conditions that may be comorbid in elderly people.
Further illustrative of the complexity of this area of research, Parmelee noted that associations of pain with depression vary across individuals and groups, depending on factors such as overall health, demographics, and personality. When considering effects on disability, what emerges is that pain predicts depression and disability; depression predicts pain and disability; and disability predicts pain and depression. But the exact nature of those linkages—whether pain and disability are independently associated with depression; or whether pain first leads to disability, which then leads to depression; or whether pain leads to both disability and depression—depends upon the study sample.
Finally, demographic differences among study groups, such as race, also complicate matters, as does an individual’s cognitive state—for instance, whether a person catastrophizes or not. How the experience of pain is constructed matters, too. That is, the link between pain and depression will depend on whether subjects are assessed in a momentary way—on the spot in a real, daily-life environment—or in a more conventional fashion that relies on retrospective self-report, where recall bias becomes an issue. The tools used to measure pain must also be taken into consideration.
Effects of cognitive function on pain
Miriam Kunz, University of Groningen, the Netherlands, discussed the relationship between pain and cognitive function in older adults. Like the pain-depression link, this association goes both ways: Pain affects cognitive function, and cognitive function affects pain. Kunz focused mainly on the latter relationship.
She began by discussing research in cognitively healthy older adults. A 2016 study she performed with colleagues assessed the relationship between cognitive function and pain in 51 cognitively healthy elderly people, with an average age of approximately 68 years, whose responses to mechanical pain stimulation were assessed by facial expressions and subjective reports (Oosterman et al., 2016). The Stroop task was used to assess cognitive inhibition, a measure of executive function that assesses subjects’ ability to inhibit their natural responses. Here, when subjects see the word “blue” spelled out in red letters, for instance, intact cognitive inhibition would allow them to inhibit reading the word “blue” and accurately report the color of the word as red. The study also assessed memory and attention. Results indicated that only (poor) executive function, and not memory or attention, was associated with more pain.
Another study of 44 healthy young and older adult volunteers found that analgesia from conditioned pain modulation (CPM), a measure of a person’s endogenous pain inhibition ability, was much less in the older subjects. Further, poorer CPM correlated with decreased cognitive inhibition with aging (Marouf et al., 2014).
Studies of patients with dementia also reveal the impact of cognitive function on pain. For instance, researchers used functional magnetic resonance imaging (fMRI) to examine brain responses to mechanical pressure stimulation in a study including 14 patients with Alzheimer’s disease and 15 age-matched controls (Cole et al., 2006). The Alzheimer’s patients showed increased brain activity in pain-processing areas of the brain compared to controls. In a study from Kunz’s group, dementia patients exhibited a decreased threshold to painful electrical stimulation compared to healthy controls (Kunz et al., 2009).
Other work from Kunz and colleagues has shown that pain-indicative facial responses to painful pressure stimulation were much higher in dementia patients compared to controls (Kunz et al., 2007). This effect was specific to pain, because other facial responses irrelevant to pain, such as smiling, showed no significant differences between groups. A more recent study, from other researchers, of Alzheimer’s patients replicated these findings (Beach et al., 2016). Kunz noted that such studies of facial expressions show that dementia patients can, in fact, communicate their pain, and so pain can indeed be assessed in this population, even though these patients can’t self-report pain as effectively.
Finally, to understand what aspects of cognitive function are important with regard to pain, Kunz examined different cognitive domains, including memory and executive function, in a 2015 study (Kunz et al., 2015). This work found that executive function was the best predictor of the response to pain in dementia patients (as it was in healthy older adults).
Lastly, looking in the other direction—from pain to cognitive function—Kunz said that while the former indeed affects various aspects of the latter, including attention, memory, and executive function, the impact depends on the particular chronic pain condition under consideration. For instance, stronger effects of pain on cognition are observed in fibromyalgia compared to headache.
One message from all of the studies Kunz described is the setup of a vicious cycle: Cognitive decline leads to increased pain, which in turn leads to more cognitive decline.
Read Part 2 of our meeting coverage here.
Neil Andrews is a science journalist and executive editor of PRF.
Image credit: simondannhauer/123RF Stock Photo.
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