Painstaking measurements

A short history of how we measure pain.

Pain has long perplexed scientists and medical professionals—it is a physiological process, but still stubbornly subjective. Only you can feel your pain, but how do you describe it?

There have been many attempts to measure pain; most of them failed. In the first half of the 19th century, Marc Colombat de l’Isere, a French doctor specialising in speech and “all diseases of the voice”, studied the pitches and rhythms of patients’ cries of pain. In the 1940s, doctors at Cornell University tried to find an objective measurement of pain by applying heat to the subject’s forehead for three seconds at a time. By noting increases or decreases in reaction, they derived a 21-point scale measured in ‘dol’ units.

Other attempts to understand pain were based on self-reporting. Such subjective reports remain the most common method of measuring pain today. The 1-10 scale can be traced back to British cardiologist Kenneth Keele, who in 1948 asked his patients to choose a score between 0, being no pain, and 3, severe pain. In the 1950s, Canadian psychologist Ronald Melzack treated a woman suffering from phantom limb pain, a condition where an amputated limb leaves behind vivid sensations, as though still attached. Melzack recorded how the patient described her pain, cateogrising these descriptions to cover all dimensions of pain.
The McGill Pain Questionnaire evovled from these categories, developed by Melzack and Torgerson at McGill University in 1971. This questionnaire presented subjects with a list of 78 words divided into four categories: sensory (throbbing, flashing, burning, etc.), affective (suffocating, frightful, cruel), evaluative (annoying, troublesome, miserable), and miscellaneous (tight, numb, freezing). After the publication of the McGill Questionnaire, descriptions of phantom limb pain changed drastically, notes sociologist Cassandra Crawford in her 2014 study, implying that the questionnaire began to influence the pain it was initially meant to measure.

Self-reported descriptions of pain can be ambiguous and difficult to understand. As essayist Elaine Scarry writes in her book The Body in Pain, “To have great pain is to have certainty; to hear that another person has pain is to have doubt.” Yet the self-reporting of pain gives insight not only into an individual’s own sensation, but the cultural and social influences that shape it. Some cultures may expect loud displays of shock and emotion in the face of pain. Others might value stoicism or, conversely, boasting of a higher pain thresholds.

A 1995 study by Fillingim and Maixner suggested that women have a lower pain threshold. However, the study identified several factors contributing to the variance: the type of stimulus, the dimensions of pain measured, individual traits of the subject, as well as the gender of the researcher inflicting pain. In a 2002 study, Fillingim et al. proposed that stereotypical gender roles tend to shape a subject’s preconception of their own ability to handle pain.

According to some studies, ethnicity can also affect the intensity of pain. A 2000 study by Sheffield et al. showed that African-Americans displayed more sensitivity to stimuli than Caucasians. In 2003, Carey and Garett found that black patients recorded worse disability than white patients. These studies are doubted by more recent research, but minorities are treated differently when it comes to pain management—a 2016 study by Singhal et al. showed that black patients are half as likely to be prescribed opioid medicines than white patients for non-definitive conditions (toothache, back pain, abdominal pain). Researchers from the University of Pennsylvania found that women are also less likely to receive opioids for pain.

A step towards a more objective measurement of pain, functional magnetic resonance imagery (fMRI) first appeared in 1991 as a grainy video of brain activity measured by changes in blood flow, translated into images. While fMRI can only objectively measure thermal pain in a controlled lab setting, not at the exact time of a broken leg on a football field, the technology highlights the location, intensity, and anxiety of pain by observing which parts of the brain ‘light up.’ fMRI results also affirm that social, cultural, and gender factors affect physiological reactions—a 2009 study by Irene Tracey, for example, found that when devout Catholics were shown an image of the Virgin Mary during periods of inflicted pain, they rated their discomfort almost a point lower than the atheists did. When shown a secular painting, their responses remained the same, suggesting that religious faith influences neurological responses.

Earlier this month, a team of researchers from the University of Pittsburgh developed ‘Painimation,’ an app that uses animations to help patients assess the type, intensity, and location of pain. This allows patients to communicate their pain without the limits of language or numerical scales. The results, published in the Journal of Medical Internet Research, showed that 80 per cent of subjects enjoyed using the scale and would continue using it.

Pain is a demanding experience, both for the sufferer and the medical industries that try to relieve it. While there are still many developments to be made, the increasingly objective measurement of pain will hopefully begin to explain the cultural and personal factors that shape a person’s experience of pain. Ultimately, this will help reduce the burden of trying to communicate pain, and ensure that the pain is properly managed.