Whether the weather influences pain? Results from the EpiFunD study in North West England

Methods. A population-based study (Epidemiology of Functional Disorders) was conducted in North West England. Subjects were mailed a questionnaire that enquired about pain on the day of completion ('any pain') and chronic widespread pain (CWP) as defined by the ACR, as well as about the potential mediating factors, sleep quality, exercise and mood, between the weather and pain. Hourly information on sunshine, precipitation, air temperature and pressure was available from a local weather station. Analysis of relationships was done by Cox regression and described as prevalence ratios (PRs) with 95% CIs. Results. Between January 2005 and December 2006, questionnaires from 2491 subjects were returned: 42% of the subjects reported 'any pain' on the day of completion, whereas 15% of the subjects had CWP. For both 'any pain' and CWP, the PR was the highest in winter (46.1 and 22.2%, respectively) followed by autumn (45.4 and 17.9%, respectively) and spring (41.9 and 14.7%, respectively) and lowest in summer (35.6 and 9.5%, respectively). Persons were less likely to report pain on days with > 5.8 h of sunshine (any pain: PR = 0.87, 95% CI 0.82, 0.93; CWP: PR = 0.56; 95% CI 0.38, 0.84) and with average temperature of > 17.5 degrees C (any pain: PR = 0.74, 95% CI 0.66, 0.83; CWP: PR = 0.40; 95% CI 0.34, 0.48). These relationships were partly explained by persons reporting taking more exercise and having better sleep quality and a more positive mood on days with sunshine and higher temperatures. Conclusions. Although a strong relationship between lack of sunshine, lower temperatures and pain reporting has been demonstrated, pain is not an inevitable consequence of such climatic conditions.