Pain is a protective mechanism that serves to warn us of potential danger. Chronic pain, however, serves no purpose, is exceptionally disabling, and affects almost 1 in 5 Canadians. Not everyone experiences chronic pain the same way: pain intensity can fluctuate throughout the day in some people but remain constant in others. Our 24-hour circadian rhythms regulate the function of our nervous and immune systems, and as a result, impact our experience of pain. Our group has shown that these rhythms play an important role in the pathophysiology of chronic low back pain through a cohort study, and now seeks to expand on these findings. 

We have therefore developed a study to further explore the circadian control of chronic pain within the context of a large population sample. All Canadian adults experiencing chronic pain, regardless of condition, are eligible. With this study, we will:

1. Examine the fluctuations in pain intensity, mood, and fatigue throughout the day;
2. Determine differences between pain conditions in pain rhythmicity; and 
3. Investigate the potential association between geographic latitude and pain experience.

Our national study is composed of two main parts: (i) a baseline survey, including information on participant demographics, geographic location, sleep habits, and pain experiences, and (ii) a symptom diary, where participants rate the intensity of their pain, mood, and fatigue at three times per day (morning, afternoon, night), over seven days. We will then assess whether differing rhythmic patterns exist between various pain conditions. Finally, we will determine the prevalence of chronic pain conditions at different latitudes, and investigate the impact of day/night patterns on pain outcomes. This will help us understand whether circadian disruption, such as that experienced by those living further from the equator, plays a role in chronic pain. Future studies will include creation of a tissue biobank from participants in this study, to help us identify specific biomarkers of pain and pain rhythmicity. 

Knowledge translation is integrated into every aspect of our project. We are developing a custom-made website, which will serve as host to the survey and its publications. It will also include a plain-language blog about chronic pain with contributions from scientific writers, a forum for participants to share their own experiences with pain rhythms, and an interactive platform that will allow survey participants to access basic data visualizations of the survey results, updated continuously as the study goes on. Our patient advisory committee, which includes patient-partners from across Canada, help guide our study and project design.

Through this work, we will come to better understand how pain fluctuates throughout the day in a variety of chronic pain disorders. This knowledge will bring us closer to determining why pain occurs and help to develop more effective strategies for its management.