Although many patients worldwide report increased joint sensitivity in the summer months each year, research on environmental effects on arthritis has not reached a definitive conclusion [1, 2]. This article will analyze various studies that have addressed this question in an attempt to consolidate results and point towards future research.
Over the last two decades, one prominent line of research about environmental effects on arthritis investigated the influence of vitamin D levels on arthritis incidence. Several experiments from the last two decades seemingly demonstrated that lower vitamin D levels (typically associated with lower levels of sunshine and fewer hours of daylight) were associated with higher incidences of rheumatoid arthritis (RA) [3]. However, other studies, such as Yazmalar et al., were not able to find a correlation between vitamin D levels and disease activity in RA patients [4, 5].
Given this discrepancy, researchers have looked into other components of seasonal weather fluctuations to explain claims that the environment affects arthritis symptoms. Another recent area of inquiry followed metrics such as minimum and maximum temperature, atmospheric pressure, and humidity that, together, distinguish each season from the others [5, 6]. A longitudinal analysis of 133 people with RA tracked each patient’s Disease Activity Score-28 (DAS-28) at five time points [6]. During those time points, the researchers tracked various weather conditions to identify potential correlations [6]. Savage et al. noted that RA disease activity lowers in sunnier and less humid conditions, while temperature has no significant correlation with a patient’s DAS-28 score [6]. Because the summer is the hottest and most humid time of the year, these findings cannot fully explain arthritis patients’ increased summer sensitivity.
In 2020, Azzouzi and Ichichou implemented an experiment focused on answering this question from a more direct route by centering their analysis on seasonal changes [5]. Using a retrospective longitudinal study conducted in Oujda City, Morocco, they measured the DAS-28 of 177 patients across 346 consultation days during three seasons (summer, winter, and spring) [5]. Meteorological parameters for each of those consultation days were recorded and analyzed alongside patients’ DAS-28 [5]. The results suggested that weather influences RA pain, with increased precipitation correlating with exacerbated pain in the summer months and increased humidity producing a similar effect during the winter [5]. These results are not without a caveat–a prior study could not demonstrate a correlation between RA flair-ups and the onset of the winter–but still sheds more light on the research question [7].
Azzouzi and Ichichou’s isolation of two different correlations between weather factors and DAS-28 scores may explain why prior studies were contradictory. The experiment was attentive to specificities relating to geography, seasonal variation, and other factors that were not major considerations in the other studies [5]. Future research on environmental effects on arthritis may benefit from greater specificity and detail to elucidate the relationship between these phenomena.
References
[1] F. Liu et al., “Seasonality of Ankle Swelling: Population Symptom Reporting Using Google Trends,” Annals of Family Medicine, vol. 14, no. 4, p. 356-358, July 2016. [Online]. Available: https://doi.org/10.1370/afm.1953.
[2] L. Abasolo et al., “Weather conditions may worsen symptoms in rheumatoid arthritis patients: The possible effect of temperature,” Reumatología Clínica, vol. 9, no. 4, p. 226-228, July-August 2013. [Online]. Available: https://doi.org/10.1016/j.reumae.2013.03.002.
[3] A. Watad et al., “Seasonality and autoimmune diseases: The contribution of the four seasons to the mosaic of autoimmunity,” Journal of Autoimmunity, vol. 82, p. 13-30, August 2017. [Online]. Available: https://doi.org/10.1016/j.jaut.2017.06.001.
[4] L. Yazmalar et al., “Seasonal disease activity and serum vitamin D levels in rheumatoid arthritis, ankylosing spondylitis and osteoarthritis,” African Health Sciences, vol. 13, no. 1, p. 47-55, March 2013. [Online]. Available: https://doi.org/10.4314/ahs.v13i1.7.
[5] H. Azzouzi and L. Ichichou, “Seasonal and Weather Effects on Rheumatoid Arthritis: Myth or Reality?,” Pain Research Management, vol. 2020, p. 410-417, September 2020. [Online]. Available: https://doi.org/10.1155/2020/5763080.
[6] E. M. Savage et al., “Does rheumatoid arthritis disease activity correlate with weather conditions?,” Rheumatology International, vol. 35, no. 5, p. 887-890, October 2014. [Online]. Available: https://doi.org/10.1007/s00296-014-3161-5.
[7] D. P. C. de Rooy et al., “Does the season at symptom onset influence the long-term severity of radiographic joint destruction in rheumatoid arthritis?,” Rheumatology International, vol. 71, no. 12, p. 2055-2056, December 2012. [Online]. Available: https://doi.org/10.1136/annrheumdis-2012-201565.