Why Pain Does Not Follow a Single Age Curve

A major new study published in Nature Medicine analyzed data from over 6.1 million people in118 countries, collected over a 35-year period (from 1990 to 2025), with the goal of mapping pain, understanding how much we experience it over the course of our lives, and how it changes with age.The key finding is that pain does not follow a single trajectory — and it does not simply worsen with age. Some types of pain become more common over time, while others peak in midlife and then decline. Patterns also vary by body region: Pain in some areas follows one course, while pain elsewhere follows another. These differences extend beyond age, with gender, place of residence, and possibly life circumstances also playing a role.This broad global picture thus leads to a deeper question: What are we really measuring when we say that a person is in pain?A Curve That Doesn’t Just RiseThe most immediate intuition is that pain must increase with aging. The body accumulates wear and tear, chronic diseases appear, and joints and muscles change. Thus, more years should mean more pain, but the data tell a more complex story.In the Nature Medicine study, the proportion of people reporting any physical pain rises from about 30% at age 5 to about 70% at age 100 and beyond. But when looking at high-intensity pain and generalized pain, the curves do not simply continue to rise: The former peaks around age 50, while the latter tends to peak later, around age 70. Average pain intensity also peaks in middle age.Patterns become more distinct when pain is examined by body region. Headache, abdominal, and facial pain tend to peak earlier in life, while musculoskeletal pain more often increases with age. Even within the musculoskeletal system, trajectories differ: Neck and shoulder pain may peak in midlife and then decline, whereas lower back, hip, and knee pain may continue to increase for longer.The first lesson, therefore, is that age is not a sufficient explanation for pain. Rather, it is one of several factors along which pain traces its course.Not Just a Sign of InjuryTo understand why this distinction is important, we need to take a step back.In 2020, the International Association for the Study of Pain revised its definition of pain for the first time since 1979. Pain is now defined as “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.” The accompanying notes emphasize a crucial distinction: Pain and nociception are not the same, and pain cannot be inferred solely from sensory neuron activity. The distinction may seem subtle, but it has important implications for how clinicians understand and care for patients.Nociception is the nervous system’s detection of potentially harmful stimuli. Pain is a distinct experience that may arise from nociception but is shaped by biological, psychological, and social factors, as well as an individual’s personal history.This does not mean that pain is imaginary when no obvious injury is found. It means the opposite: Pain is real, but its reality is not necessarily limited to the presence of an injury.When the Pain System ChangesResearch over the past few decades has shown that the nervous system is not simply a cable that faithfully transmits a signal from the tissue to the brain. It can change, become more sensitive, and alter the way it interprets and amplifies stimuli. This is one of the concepts that help us understand nociceptive plasticity.The term refers to a form of pain associated with an alteration in nociception that cannot be adequately explained by the presence of tissue damage or a lesion in the somatosensory system. It is not synonymous with “psychological pain” and does not replace other categories: nociceptive, neuropathic, and nociplastic mechanisms can coexist in the same person.People with nociplastic-related characteristics may experience pain in multiple regions of the body, sleep disturbances, fatigue, cognitive impairments, and increased sensitivity even to nonpainful stimuli. Research also points to the involvement of brain networks, immune mechanisms, and peripheral factors.Why Do Some Recover While Others Don’t?Another question arises when observing the transition from acute to persistent pain.Acute pain, in most cases, serves a protective function. It signals that something is wrong and prompts us to protect the affected area. But in some people, the pain does not go away even after the underlying cause has been resolved.What determines this transition? A systematic review of studies on the transition from acute to chronic pain found associations between chronicity and various psychosocial factors: Among those studied, depression and fear-avoidance emerge in a substantial portion of the literature.This finding, too, should be interpreted with caution: It does not mean that depression or anxiety simply cause pain. It means that the persistence of pain often stems from the interaction of multiple factors. An initial episode, individual vulnerability, sleep, physical activity, emotional state, living and work environments, and access to care can all contribute to determining the subsequent course of the condition.Women and Men Follow Different Pain TrajectoriesThe study in Nature Medicine also reveals a consistent difference between the sexes. Women report pain more frequently than men: The prevalence ratio is approximately 1.16 for any pain, 1.52 for high-intensity pain, and 1.50 for generalized pain.This is an important finding, but one that warrants careful interpretation. Experimental research on sex and gender differences in pain has produced a more complex picture than might be expected. A systematic review of more than a decade of laboratory studies found differences in some experimental settings, but no consistent pattern across all types of pain. Findings related to hormonal, psychological, and social factors have also been mixed.These findings come with an important caveat: Differences in pain between women and men do not point to a single “female biology of pain.” Rather, they may reflect the interplay of biology, exposure to different health conditions, personal history, social factors, and differences in how pain is recognized and treated.Where You Live Also MattersAfter age 40, the trajectories of bodily, joint, and lower back pain diverge much more markedly between countries with different levels of development. This is perhaps the most surprising finding of the Nature Medicine study. Among individuals aged 80 or older, the difference in prevalence between contexts with low and high Human Development Index values reaches approximately 30.6 percentage points for any type of bodily pain, 21 percentage points for joint pain, and 20.2 percentage points for lower back pain. These data invite a broader question: How much of what we describe as pain associated with aging reflects the circumstances in which a person grows older? Occupation, financial resources, access to care, physical activity, diet, comorbidities, and access to diagnosis and rehabilitation can all profoundly shape an individual’s experience over time.The literature on low back pain, for example, has found particularly strong associations with educational level and socioeconomic status. A review that pooled 41 studies involving over 2.1 million adults demonstrated just how complex the relationships between social determinants and chronic low back pain are.A meta-analysis of 45 studies involving approximately 175,000 people found that lower socioeconomic status was associated with a greater likelihood of chronic pain. The authors noted, however, that the studies were heterogeneous and called for more data, particularly from countries that have been underrepresented in the research.Pain, therefore, does not merely tell the story of a body. It can also tell the story of the conditions in which that body has lived.Low Back Pain: A Paradigm ShiftLow back pain is perhaps the most obvious example. According to estimates from the Global Burden of Disease study, in 2021 low back pain accounted for approximately 70 million disability-adjusted life years, more than any other single cause. But its significance stems not only from the number of people affected. It also serves as a model for understanding why the old framework, pain = injury = treatment of the injury, is insufficient for a significant proportion of patients.The World Health Organization’s guidelines for chronic primary low back pain emphasized that pain occurs within a personal and social context. They recommend a biopsychosocial approach that may include physical and psychological interventions, education, and, when appropriate, pharmacologic treatment.From ‘Where?’ to ‘Why?’ in Pain AssessmentThis is perhaps the most interesting conclusion that can be drawn from the large epidemiologic study and the most recent research: Pain changes over the course of a lifetime, with different trajectories depending on age, anatomic location, gender, and socioeconomic context.Neurobiological research reminds us that the experience of pain does not necessarily correspond to tissue damage and that the nervous system can alter the way it processes signals. Studies on the chronicity of pain show that persistent pain may be associated with a combination of biological, psychological, and social factors. And research on social determinants suggests that living conditions can contribute to substantial differences in the experience of pain.Clinicians have traditionally looked for pain’s source in a worn joint, damaged nerve, inflammation, or spinal problem. But these findings suggest that such explanations may not tell the whole story. As the study in Nature Medicine shows, pain is not simply a trajectory that progresses with age; it unfolds over time, shaped by the body, the brain, and the broader social environment.This story was translated from Univadis Italy, part of the Medscape Professional Network.