Self-perceived weather sensitivity and joint pain in older people with osteoarthritis in six European countries: results from the European Project on OSteoArthritis (EPOSA)

Osteoarthritis (OA) is a degenerative joint disease, which is mainly characterized by damage and loss of articular cartilage and changes in adjacent bone, including osteophytes and subchondral bone sclerosis [1, 2]. OA is the most common cause of chronic pain in older persons and the leading cause of disability [3]. People with OA frequently report that the severity of their pain is influenced by weather conditions [4]. The impairment of well-being and/or incidence of symptoms or exacerbations of diseases related to weather is termed weather sensitivity [5]. Research on the effect of self-perceived weather sensitivity on joint pain in people with OA is scarce. Knowledge gained on the perceived influence of weather on joint pain in older people with OA could be applied in the development of coping strategies for dealing with joint pain and climatologic conditions in this disease group. The present study aims to examine whether there are differences in joint pain between older people with OA who reported to be weather-sensitive and those who did not in six European countries with different climates.

Research on the perceived influence of weather on pain is mainly conducted in chronic pain patients and diagnostic differences in subgroups of patients are rarely examined [6, 7]. Jamison et al. [6] investigated the differences in the perceived influence of weather on pain among 558 chronic pain patients, living in four different climates in the United States of America (USA). The most frequent complaints in this group were lower back pain and arthritis. Cold and damp weather conditions were perceived to influence pain most. The weather-sensitive and non-weather-sensitive chronic pain patients did not differ in self-reported pain intensity. Notably, chronic pain patients who had been told that they had arthritis tended to report greater weather sensitivity to weather changes. However, the diagnoses were based solely on self-report, without objective medical confirmation.

In an Australasian study, Ng et al. [8] found that the majority of OA-patients reported weather sensitivity. Various physiological and psychological explanations have been offered for the greater sensitivity to weather in OA-patients [6, 8‐10]. It has been suggested that because tendons, muscles, bones and scar tissues are of varied densities, differential expansions and contractions due to atmospheric changes results in pain at sites of microtrauma [6, 8]. In addition, alterations in temperature may increase stiffness in the joints and may trigger subtle movements that can heighten a nociceptive response [6, 9]. It has also been suggested that weather affects mood, resulting in an alteration of pain perception [6, 8‐10]. Negative mood is associated with high levels of pain in people with OA [11, 12]. Rainy weather conditions may adversely affect mood and thus may indirectly affect pain perception.

The specific objectives of the present study are: (1) to examine whether there are differences in perceived joint pain between weather-sensitive and non-weather-sensitive people with OA in six European countries with different climates; and (2) to identify characteristics of older persons with OA that are most predictive of perceived weather sensitivity.

The mean age of all 712 participants with OA was 73.5 (SD = 5.5) years. Of all participants, 484 (72.0%) were female and 469 (67.2%) participants reported that weather affects their joint pain.

The characteristics of weather-sensitive and non-weather-sensitive participants are presented in Table 1. The weather-sensitive participants were more often female and lower educated. They had a lower sense of mastery and were more anxious and depressed compared to the non-weather-sensitive participants. The weather-sensitive participants used additional pain medication on more days than the non-weather-sensitive participants. Weather-sensitive and non-weather-sensitive subjects did not differ in age, partner status, BMI, number of chronic diseases and outdoor physical activity.

This study aimed to examine whether there are differences in perceived joint pain between weather-sensitive and non-weather-sensitive people with OA in six European countries with different climates and to identify characteristics of older persons with OA that are most predictive of self-perceived weather sensitivity. The results confirmed that weather-sensitive older people with OA experience more joint pain than their non-weather-sensitive counterparts. Women and more anxious people were more likely to report weather-sensitivity. The results also revealed that older people with OA from Spain and Italy were more likely to report weather-sensitivity compared to those from Sweden.

Our study showed that weather-sensitive people with OA reported more pain than non-weather-sensitive persons with OA. After adjusting for several confounding factors, the association between self-perceived weather sensitivity and self-reported joint pain remained present. Previous research in chronic pain patients revealed conflicting results concerning differences in experienced pain between weather-sensitive and non-weather-sensitive patients [6, 7]. In these studies, self-perceived weather sensitivity in subgroups of chronic pain patients was not examined. This study focused especially on older people with OA and confirmed that self-perceived weather sensitivity is related to pain perception in this specific group.

Our study further showed that approximately two thirds of the participants indicated themselves as weather-sensitive. Most of the weather-sensitive people with OA reported damp/rainy and/or cold weather as affecting their pain. Hot weather conditions were less frequently reported as influencing pain. Similar results have been found in previous studies with chronic pain patients and rheumatology patients [6, 8]. Several explanations have been suggested to account for the effects of damp/rainy, cold and hot weather conditions on pain [6, 8‐10]. Changes in temperature and humidity may influence the expansion and contraction of different tissues in the affected joint, which may elicit a pain response [6, 8]. In addition, low temperatures may increase the viscosity of synovial fluid, thereby making joints stiffer and perhaps more sensitive to the pain of mechanical stresses [6, 9]. Another postulation is that weather affects mood, resulting in an alteration of pain perception [6, 8‐10]. This suggestion is not supported by our findings. The weather-sensitive people with OA were more anxious than those who were non-weather-sensitive. However, the association between self-perceived weather sensitivity and self-reported joint pain was still present after correcting for several confounders, including anxiety and depression. This suggests that emotional distress does not confound or mediate the association between self-perceived weather sensitivity and joint pain in older people with OA.

Although most weather-sensitive older people with OA reported to be sensitive to damp/rainy and/or cold weather, the common belief that joint pain in OA becomes worse by living in a cold and damp climate is not supported by our results. Our findings showed that weather-sensitive older people with OA in a cold and wet climate reported even lower pain intensity levels than those in a warm and wet or warm and dry climate. Jamison et al. [6] found that chronic pain patients in a colder climate did not report more pain than patients in warmer climates and suggested that the body establishes an equilibrium in relation to the local climate so that changes in weather trigger an increase in pain regardless of the prevailing meteorological conditions. Weather (in)stability might be an explanation for the differences in experienced joint pain between the three local climate types, however this was not assessed in this study.

Our findings showed that sex, country and anxiety are independent predictors of self-perceived weather sensitivity in older people with OA. It was found that women were more likely to report weather sensitivity than men. This seems to be in line with the findings of Von Mackensen et al. [5]. They found that women in the general population report a strong influence of weather on their health more often than men. Our results showed that more anxious people were more likely to indicate themselves as weather-sensitive persons. Possible explanations could be that poor mood might increase subjective complaints of pain or more anxious people with OA might tend to blame their symptoms on something they can understand but cannot control more than less anxious people with OA [9]. However, our findings showed that mastery is not an independent predictor of self-perceived weather sensitivity in older people with OA. The disease course of OA is often characterized by the alternation of stable periods of varying length, characterized by a low level or absence of symptoms with periods of flare-up or exacerbation [22]. The uncertainty about the recurrence of pain may lead to anxiety in people with OA and this might encourage the desire to have an explanation for the worsening of their pain. As a consequence, more anxious people with OA might be more likely to report weather as a pain-generating factor than less anxious people with OA.

Our findings also revealed that older people with OA from Spain and Italy were more likely to report weather sensitivity compared to older people with OA from Sweden. The climates in both Mediterranean countries are warmer compared to the climate in Sweden [21]. As a result, older people with OA in Italy and Spain may be more often outside compared to those in Sweden and the degree of exposure to the weather may vary between these people. As a consequence, they may be more aware of the effect of weather on their pain and are more likely to report weather sensitivity.

Another possible explanation might be differences in weather (in)stability between both Mediterranean countries and Sweden. Weather changes may have a greater impact on joint structures and pain perception in people from Southern Europe than in people from Northern Europe. As a result, people from Spain and Italy may be more aware of the effect of weather changes on their pain and are more likely to report weather sensitivity than people from Sweden.

There are several strengths in this study. To our best knowledge, the present study is the first large-scale study that examines self-perceived weather sensitivity and joint pain in older people with OA in Europe, correcting for a wide range of confounding factors. Prior studies were performed in the USA and Australasia and were mainly focused on self-perceived weather-sensitivity and pain in less specific groups [6‐8]. The current study used a population-based approach and focused on one disease group. The assessment of clinical OA was standardized across countries using the ACR classification criteria. The current study increased insight into the characteristics profile of weather-sensitive people with OA in a general population of older persons across Europe. This may help to identify weather-sensitive older people with OA. Early treatment of weather-sensitive individuals with OA using cognitive and psychological interventions may reduce suffering and may help them to maintain a functionally effective lifestyle [23].

Some limitations of this study have to be acknowledged. Participants were considered as weather-sensitive persons, when they indicated that damp/rainy, cold, and/or hot weather affected their joint pain. If subjects noted that their joint pain was not affected by one of these weather conditions, they were considered as non-weather-sensitive persons. This classification method did not take into account whether participants’ joint pain could be affected by other weather conditions, such as changes in barometric pressure [6]. Furthermore, it is important to acknowledge some caveats with regard to the use of three local climate types. Two local climate types were only based on one country each. Spain represented a warm and dry climate and Sweden represented a cold and wet local climate. Only a warm and wet climate was represented by more than one country. Differences in experienced joint pain between the three climates may be due to other country-related factors. For example, differences in socio-cultural factors across countries may play a role [24, 25].

Future research is needed to investigate actual versus perceived effects of weather on pain in weather-sensitive and non-weather-sensitive people with OA. In particular, longitudinal, prospective studies are needed to evaluate the relation of daily climatologic conditions to pain in older people with OA. The use of objective weather data may increase insight into the seasonal effects on joint pain in people with OA and the differences between countries.

In conclusion, this study showed that the majority of older people with OA in the general population believe that weather affects their pain. Weather-sensitive older people with OA experience more joint pain than non-weather-sensitive older people with OA. Women and more anxious people are more likely to consider themselves as weather-sensitive. Older people with OA from Italy and Spain were more likely to report weather sensitivity than those from Sweden. Weather changes may have a greater impact on joint structures and pain perception in people from Southern Europe than in people from Northern Europe. The current results emphasize the importance of considering weather sensitivity in daily life of older people with OA and may help to identify weather-sensitive older people with OA.