How is pain measured?

Anyone who's ever dealt with pain — and that's nearly everyone — understands it exists on a spectrum. There’s minor pain, like a paper cut, and then there's severe pain, such as passing a kidney stone or childbirth. Yet within that spectrum, it becomes difficult to pinpoint. How intense is the pain you’re enduring? Does it necessitate strong painkillers, or will something milder like Tylenol suffice? Will it last a few hours or linger for months?

Pain is deeply personal and varies considerably from individual to individual. Women, for instance, are generally more sensitive to pain, as are redheads, those who are depressed, unwell, or inactive [source: Woznicki]. Countless factors influence pain, such as the fact that people tend to tolerate it better on their dominant side (right side for right-handed individuals, left for left-handed) [source: Woznicki].

Pain can manifest in various forms. For example, tissue pain, like muscle injury, usually causes a dull, aching sensation, while nerve pain often presents as a burning or shooting pain. Moreover, pain can be categorized as either acute (sharp and brief) or chronic (persistent).

Given the wide range of pain experiences, it’s no surprise that pain can be difficult to describe — and even harder for doctors to measure. This challenge has led researchers to dedicate decades to developing reliable methods for assessing pain. In the 1940s, medical scientists introduced the 'dol,' a unit used to measure a patient's reaction to having a point on their hand burned. (Interestingly, the dol was primarily tested on women in labor, a group experiencing intense pain.)

The concept of the dol was later incorporated into a device called a dolorimeter. This device would apply heat or stimulation to a patient’s skin and measure their response. A more modern version, known as a palpometer, follows the same approach, but uses pressure. These devices are still in use today, though they haven’t yet gained widespread acceptance as reliable tools for measuring pain.

Currently, the most common method of assessing pain is through self-reporting by patients. Hospitals and physician offices often use a pain identification chart to help individuals rate their pain on a scale from one to ten. When patients are unable to verbally describe their pain due to a medical condition or language barrier, medical professionals refer to a chart that pairs pain levels with facial expressions.

Naturally, the self-report method has its limitations. Pain is inherently subjective, and expressing it accurately can be difficult. Some individuals, due to cultural or social constraints, might understate their pain or fail to communicate it clearly.

Luckily, advances in medical technology hold promise for more accurate pain assessments in the future. In 2013, researchers at The University of Colorado-Boulder used brain scans to map pain. By studying how research subjects’ brains responded to different levels of heat, the researchers identified distinct neurological patterns associated with varying levels of pain. This breakthrough enabled the measurement of pain on an objective scale for what might be the first time in history.

While the use of imaging technology for everyday pain measurement is still a distant goal, it has contributed significantly to our understanding of how the human brain responds to pain, paving the way for deeper exploration and potential applications in the future.