Pain and Weather—A Cloudy Issue
Patients suffering from chronic pain frequently attribute their symptoms to changes in the weather. In fact, a study revealed that a surprising 92% of patients suffering from widespread chronic pain believed that their symptoms were exacerbated when the weather was humid or cold.1
This perceived correlation has even become codified in the English language with such expressions as “feeling under the weather” or being “right as rain.” However, scientific studies exploring the association between pain and meteorological phenomena have reached little consensus in results, even when studying the same type of pain caused by the same disease.2-7
The answer to such a relationship—if one exists—has important implications for both the lives of patients suffering from chronic pain and physicians in their ability to recommend and develop pain management treatments.
Much of the research that has attempted to objectively evaluate the pain-weather association has focused on how specific meteorological parameters influence various forms of arthritis. This may reflect the fact that patients with arthritis are substantially more likely to attribute pain to weather conditions than patients with any other chronic pain condition.8
Given the high proportion of chronic pain patients who attribute their symptoms to shifts in the weather, Redelmeier and Tversky looked into whether or not the intensity of arthritic pain actually matched preconceived beliefs of an association with meteorological factors. The results indicated that even among arthritis patients who contend that their well-being is influenced by the weather, self-assessed pain indices showed no relationship between pain intensity and barometric pressure, temperature, or humidity.9 The researchers hypothesized that individuals ascribe and maintain a perceived correlation where none exists due to “selective matching,” the propensity to fixate on salient coincidences.9
Investigations into the relationship between osteoarthritic pain and weather have yielded equivocal results as well. Wilder’s group at the Arthritis Research Institute in Florida found very little association between osteoarthritic pain and temperature, barometric pressure, or precipitation; increasing barometric pressure in women with hand osteoarthritis was the only variable significantly correlated with pain (P<0.001).10 This is consistent with some published results,2,9,11-13 but not with others.1,3,6,14
Conversely, analysis of patients with osteoarthritis of the hip found a more meaningful association: large increases or large decreases in atmospheric pressure were significantly correlated with increases in reported pain.15 Fifty-three participants with end-stage hip osteoarthritis (with or without pseudocysts) kept a daily record of their pain level using a visual analogue scale (VAS). The researchers then retrieved and matched the meteorological data from the nearest weather station. The results indicated that the precipitation, temperature, and presence of subchondral pseudocysts shared no link with pain severity.15
A population-based study of arthritic patients in northwest England concluded that rheumatic patients were more likely to report less pain on warmer days with more hours of sunshine than on colder days with less sunshine.16 In that study, 2,491 patients with rheumatoid arthritis returned self-report questionnaires designating the onset and degree of pain on the day of completion. The probability of reporting either “chronic widespread pain” or “any pain” was highest in winter (22.2%), followed by fall (17.9%), then spring (14.7%), and finally summer (9.5%). Likewise, the severity of self-reported pain was highest in winter (46.1 on the American College for Rheumatology score) and lowest in summer (35.6).16
However, shortening length of sunshine has been correlated with depression, somatization, and anxiety, which may influence the onset of painful episodes.17 Although the data suggested a correlation between weather and pain, the researchers cautioned against generalization of results, pointing out that the relationship did not appear direct or causal, but rather, influenced in part by lifestyle factors or moods associated with colder days and less sunshine.16 Precipitation did not affect the onset of pain in rheumatic patients.16
Previous studies have also reported a correlation between pain and temperature or barometric pressure in rheumatic patients.8,18 However, these studies either did not blind the participants to the research hypothesis, lacked a control window, or relied on memory recall ex post facto.
Why Pain Is Associated With Weather
The mechanism by which weather affects pain is not clearly elucidated, and is still avidly contested in the scientific community. However, there are several theories that may rationalize how meteorological changes influence perception of pain.
One theory states that when barometric pressure drops (as often happens before the onset of bad weather), the surrounding air pushes with less force against joints, permitting tissues to expand, which may then put pressure on the respective joints.19 This may explain aggravated joint pain in arthritis patients, but does not illustrate how pressure changes may affect other chronic pain conditions (Figure 1).
Randomized, controlled experiments at Nagoya University in Japan demonstrated in nerve-injured rats that lesion of the inner ear alleviates pain-related behavior induced by decreasing barometric pressure.20 The results indicate that the inner ear apparatus stimulates nociceptors when pressure decreases, but not when temperature decreases.20 The researchers proposed that pressure differences between endolymph and perilymph of the inner ear aggravate mechanical hyperalgesia via three primary mechanisms: control of descending nociception, hormonal changes, and sympathetic activation.20
A second theory involves dropping temperatures. A study of 200 patients with osteoarthritis of the knee concluded that each progressive 10-degree decrease in ambient temperature corresponded to an increase in knee pain of 0.1 on the Western Ontario and McMaster Universities Arthritis (WOMAC) Index. Furthermore, precipitation, low temperature, and low pressure may stimulate pain, possibly by increasing swelling in the joint capsule.7