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10 Articles in Volume 16, Issue #4
Achilles Tendon Injuries
Brain Trauma in Sports
Genetic Testing: Adjunct in the Medical Management of Chronic Pain
Letters to the Editor: Sleep Apnea, SPG Blocks for Migraines, Pancreatic Pain, CDC Guidelines
Pain and Weather—A Cloudy Issue
Phulchand Prithvi Raj, MD, Pioneer in Pain Management, Dies at 84
Physical Medicine & Rehabilitation
Preventing Chronic Overuse Sports Injuries
Sports-Related Pain: Topical Treatments
The “Missing Link” in the Physiology of Pain: Glial Cells

Pain and Weather—A Cloudy Issue

Numerous peer-reviewed studies have attempted to validate a correlation between patient pain and meteorological conditions, but documenting any sort of repeatable linkage remains a scientific enigma.

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.

Patients often complain of worsening symptoms during changes in weather.The Relationship of Arthritis to Weather

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

In studying the biological effects of decreasing temperature and pressure on neuropathic or chronically inflamed rat models, Jun Sato formulated 4 mechanisms that may aggravate pain. First, low pressure directly triggers the sympathetic nervous system to stimulate chronic pain via local ischemia and vasoconstriction.21 Second, low temperatures increase heart rate, noradrenaline, and blood pressure, although the exact mechanism remains unclear.21 Third, cold temperatures trigger the release of adrenocorticotropic hormone and epinephrine, which aggravate pain via vasoconstriction, ischemia, and local decrease in temperature.21 Fourth, low temperatures can stimulate mast cells to release analgesic substances that heighten nociceptor activity.22

Alternatively, changes in barometric pressure may augment cytokine pathways. Strusberg et al demonstrated that applying hydrostatic pressure to chondrocytes increases expression of tumor necrosis factor-α and interleukin 6.1 Increased cytokine activity may damage host cells and help explain changes in perception of pain.

Canadian researchers Ngan and Toth have hypothesized that cold temperatures directly stimulate damage-sensing mechanisms via activation of voltage-gated channels.23 Others have studied transient receptor potential cation channel subfamily M member 8 (TRPM8) channels in temperature sensitivity24,25 and cold-induced ionic conduction.26 However, Ngan and Toth noted that there are likely a multitude of other factors that contribute to weather sensitivity, such as increased likelihood to remain inside on cold days.23

Alterations in barometric pressure can induce a state of transient disequilibrium that sensitizes nerve endings as well. Sensitized nerve endings may subsequently aggravate pain caused by changes in temperature or humidity. Experiments have shown that arthritic patients in climate-controlled rooms report greater pain when barometric pressure decreases and humidity increases, but not when only one of these two variables is changed.27

Other Weather-Related Associations

Different case-crossover studies evaluating the relationship between rheumatoid-type pain and weather changes have either concluded that only temperature affects middle-age patients (with no significant factors in any other age groups)28 or that high wind speeds increase risk of hip fracture without any other significant correlation to weather changes.29 A study of 2,121 patients admitted for hip fractures found increased frequencies of hip fractures on days with higher wind speeds; in fact, the windiest days had a 32% higher risk for hip fracture compared to calm days. Precipitation had no statistical correlation with hip fractures.29

A meta-analysis by Smedslund and Hagen in 2011 analyzed 9 different studies that investigated the pain-weather relationship; it concluded no correlation between rheumatoid pain and temperature, humidity, or pressure.30 However, they also concluded that statistical analyses of individual participants from 2 of the 9 studies uncovered that these 3 meteorological factors do influence pain in about 25% of rheumatoid patients. The data suggests that a minority of those suffering from rheumatoid arthritis may be more sensitive to meteorological changes, at least in regard to how these shifts stimulate rheumatoid pain. 30

Barometric Pressure

The way changes in atmospheric pressure aggravate joint pain deserves special attention, not only because it is more consistently tied to onset of pain than other meteorological parameters, but also because of its unobservable quality to the patient. As Brennan et al keenly note, despite the prevailing myth that rheumatoid patients can predict rainfall by the “aches in their bones,” most studies exploring the relationship conclude no correlation exists between arthritic pain and precipitation.2,9-13,15,16,28,31

Conversely, a handful of studies have connected changes in barometric pressure­—a parameter not consciously discerned—to onset of pain2,6-8,10-13,18 even though the extent of correlation has been contested. Controlled studies on neuropathic and rheumatoid-like rat models similarly indicate that drops in barometric pressure or temperature aggravate mechanical allodynia and hyperalgesia.21 This points to a physiological mechanism rather than a psychological process linking arthritic pain to barometric pressure.

Nonetheless, studies have produced mixed results regarding whether or not barometric pressure affects joint pain. Some researchers have found that increasing barometric pressure aggravates arthritis pain; in a 2007 study, researchers found a positive correlation tying temperature and pressure change to pain severity in osteoarthritic patients (Ppressure = .02, Ptemperature = .004).7 Other studies have reported that women are more sensitive than men to changing meteorological parameters (62% vs. 37%);6 yet others concluded that no such association exists between arthritis pain and barometric pressure.9

Other Types of Pain

Comparatively less research has been devoted to studying the link between weather and other sources of chronic pain, including fibromyalgia, sickle cell disease, migraines, lower back pain, and temporomandibular joint disorders. What little data is available may not accurately reflect the complex interactions that aggravate pain in these cases.

Sickle Cell Pain

Molokie, Wang, and Wilkie have proposed that nervous system overstimulation and damage from sickle cell disease result in neuropathic pain that manifests as both allodynic and hyperalgesic.32 However, the notion that sickle cell patients experience neuropathic pain has not been widely accepted by the medical community.32

As with arthritis, sickle cell disease (SCD) studies have reached contradictory conclusions. Experiments conducted in Georgia and London both report no association between temperature and frequency of hospital admissions.33,34 These results contrast studies done in Virginia, Canada, and France, which indicate a statistical significance between lowering temperature and pain35,36 or that high or low temperatures increase emergency room visits for SCD patients.37 Yet other studies have correlated sickle cell pain with certain meteorological factors, such as wind speed, but not others.5,6

A comprehensive meta-study that assessed the results and merit of several dozen SCD studies contended that overall, the connection between cold temperatures and wind speed with hospital admissions had significant outcomes for SCD patients.38 However, the researchers noted that no clear link has causally tied these environmental factors to pain, since few robust studies have demonstrated the mechanisms that aggravate sickle cell pain.38 The exact effects of cold and windy weather on SCD are thus difficult to discern, given the multivariable interaction of numerous other factors, including socioeconomic status, climate, physical activity, and likelihood of infection.38

Neuropathic Pain

Among patients who suffer from neuropathic pain, Ngan and Toth concluded that Chinook winds (winds that undergo adiabatic warming across the western North American prairies) had very little relationship with pain.23 In fact, the presence of Chinook winds was found to actually be neuroprotective, although the mechanism by which Chinooks alleviated neuropathic pain was unknown. Only when external temperatures plummeted below -14 degrees Celsius was neuropathic pain exacerbated by Chinook winds.23 This may support a hypothesis that only extreme weather conditions are correlated to specific pain conditions.

Migraine Pain

Another Canadian-based study exploring the relationship between pain and migraine headaches concluded that the presence of Chinook winds increased the likelihood of a migraine by about 3%.39 This correlation was especially prevalent in patients over age 50. However, the study only included 13 subjects and utilized self-report headache diaries, so the internal validity may be disputed.39

Migraineurs also frequently attribute the onset of headaches to specific environmental triggers, including bright sunlight, air quality, pressure change, and even certain odorants. But can migraines be predicted by the weather? A German study investigated this question and examined the prevalence and intensity of migraine attacks in 100 patients. The researchers then correlated the attacks with temperature, humidity, and atmospheric pressure over a 1-year period. They found that although no meteorological variables established a significant association with migraine onset or severity, statistical analyses of individual participants revealed that pressure, temperature, and humidity did influence migraines in approximately 13% of migraineurs (P<0.001).40 As in the meta-analysis study by Smedslund and Hagen, the results imply that some individuals are more weather sensitive than others. These findings may clarify why studies that have explored the pain-weather phenomenon have yielded equivocal and contradictory results—some participants may respond differently to changes in weather parameters than others.40

Investigations have also explored phenotypic changes that may explain why being exposed to cold external temperatures with wet hair causes posterior eye pain and sinus headaches. Normally, hair protects against heat loss, but wet hair in hypothermic environments may accelerate heat loss. Cooled venous blood from the head and nasal mucous membranes drains into intracranial dural sinuses—a process known as “selective brain cooling.”41 In order to mitigate brain cooling, mucus accumulates as sinus ostiums close, thus reducing air flow through paranasal sinuses; combined with vasomotor changes, blood and cerebral spinal fluid (CSF) are cooled. Excessive CSF cooling may hinder neuron function and lead to sinus headaches.41

Fibromyalgia Pain

Unlike most sources of chronic pain, research investigating the association between fibromyalgia pain and weather has reached more consistent conclusions. Smedslund et al evaluated the meteorological and psychological factors that may influence fibromyalgia pain in women.42 Only rising barometric pressure was significantly correlated with increasing pain; humidity, temperature, solar flux, and psychological variables had no impact on reported pain.42 The researchers concluded that the evidence for the association between weather and pain from fibromyalgia was limited at best.42

This is consistent with findings by Fors and Sexton, who found no relationship between fibromyalgia pain and changes in temperature, barometric pressure, sunlight, cloudiness, or humidity in 55 female patients previously diagnosed with fibromyalgia.43

Dutch researchers at Utrecht University similarly investigated how temperature, pressure, precipitation, humidity, and sunshine were tied to fibromyalgia pain.44 The results indicated that higher pain scores were weakly tied with days of higher humidity or less sunshine, but this correlation was very weak; for example, days with a full hour of extra sunshine corresponded to a 0.005 decrease in pain on a 5-point pain scale.44 Thus, at least with regard to fibromyalgia, shifting weather conditions appear to have very little, if any, effect on chronic pain.

Back Pain

A pilot study by Falkenbach, Schuh, and Wigand concluded in 1998 that even though pain worsened in 73% of patients suffering from ankylosing spondylitis as a result of changes in the weather, there was little uniform consistency in which changes elicited pain.45 Notably, the researchers only interviewed patients at one particular spa location, and asked them if they believed weather influenced their pain, and which weather conditions did so. Without a control group, few clinically meaningful conclusions can be drawn.

A more robust, comprehensive case-crossover study of 993 Australian patients evaluated the onset of lower back pain to 7 common meteorological factors—precipitation, humidity, barometric pressure, gust speed, wind speed, wind direction, and temperature.31 Of the 7 factors studied, only 2—high wind speed and gust speed—were weakly correlated with onset of lower back pain, but not deemed great enough to be clinically relevant. The pressure, precipitation, humidity, temperature, and wind direction shared no relationship with back pain onset.31

TMJ Disorders

In patients with temporomandibular joint (TMJ) disorders, a 2012 pilot study by Edefonti et al indicated that alterations in temperature, relative humidity, and barometric pressure influenced pain in 5 out of 7 patients.46 Although only 7 female subjects were included in the sample, each participant was outfitted with a data logger that recorded the temperature, pressure, and humidity; similar to the case-crossover method, this approach provided more accurate meteorological parameters at the time of pain onset rather than relying on local weather station data.46 A search of PubMed did not find any follow-up studies to confirm these findings.

What to Conclude?

With such seemingly conflicting results, can any conclusions be drawn? First, as with investigating the cause of any complex phenomenon, it is especially important to note the experimental design each researcher employed when weighing the merit of respective studies.

Using conventional research designs makes studying the influence of weather on pain methodologically challenging given the transient nature and brief induction time of weather changes. For this reason, the case-crossover method may provide useful information in future studies about how subtle shifts in the weather influence pain.

Rather than collecting data retrospectively from a weather station, the case-crossover method records the weather parameters within individual microclimates. Participants function as their own controls by recording the case window (meteorological variables at the time of pain onset) and the control window (weather variables one week earlier and one month earlier); consequently, the case-crossover method mitigates the time-invariant
factors that may confound other research methods.31

Second, it seems that overall, weather has little deterministic impact on widespread chronic pain, at least as a phenomenon that can be generalized to chronic pain caused by any number of changing meteorological variables. Studies that typically report the strongest correlation between meteorological phenomena and onset of pain are often poorly designed, utilizing self-report mail surveys and small sample sizes, not blinding participants to the research hypotheses, or relying on subjective memory recall.8,18,45,47 More robust studies often report either no association between weather and pain,9,28 or if such an association exists, it is only under specific conditions.10,15,23,29,31,42

Third, the debate over the extent to which weather affects pain intensity is far from over. Many experts who have devoted decades of work to medical climatology attest that certain meteorological factors—such as changing barometric pressure or temperature—do aggravate pain, including Dr. Robert Jamison, Harvard Medical School’s professor of anesthesiology and psychiatry.19 Other experts, however, including renowned cognitive psychologist and Nobel Prize laureate Amos Tversky, doubt a physiological basis linking weather to chronic pain.9

If such a relationship does exist, it is likely not directly causal, but may reflect a complex, multifactorial interaction of other variables. At the same time, there may be some credence to the claim that some individuals with chronic pain are more sensitive to meteorological changes than others.30

Fourth, it is clear that more research is required to clarify the inconsistency of the data and explore other medical conditions that elicit chronic pain. Few, if any, peer-reviewed published journals have reported how weather may affect pain caused by systemic lupus erythematosus, carpal tunnel syndrome, diabetic neuropathy, advanced stage cancers, or endometriosis. Further research with a focus on wider populations and utilizing the case-crossover methodology may help define which types of weather factors are deterministically correlated to specific medical conditions.

Last updated on: May 17, 2016
Continue Reading:
Letters to the Editor: Sleep Apnea, SPG Blocks for Migraines, Pancreatic Pain, CDC Guidelines

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