Rising Temperatures Associated With Uveitis Onset

BEIJING, CHINA – AUGUST 01: A man covers his head against the heat while walking at Chang’an Avenue on August 1, 2018 in Beijing, China. The highest temperature on Wednesday has reached 37 Celsius degrees in Beijing. (Photo by Visual China Group via Getty Images)
Investigators reviewed 12 years worth of climate data and uveitis prevalence from mainland China to evaluate whether a connection exists.

In a first-of-its-kind study, research published in the British Journal of Ophthalmology shows  rising temperatures can affect large-scale uveitis onset.

The investigation used data collected from 12,721 patients from 631 counties (from 31 provinces) of mainland China with uveitis reporting to the First Affiliated Hospital of Chongqing Medical University. All participants had onset dates between January 2006 and December 2017, and data was extracted that included the month and location of the onset. 

Climate data was matched from the nearest meteorological station to create the climate-uveitis panel data.  

Between 2006 and 2017, the researchers found that a monthly increase in temperature of 1° C was associated with a rise in approximately 2 uveitis reports per 1000 individuals (95% CI 0.00059 to 0.0029). They also observed a clear 0 to 3 months of cumulative lagging effect across all types of uveitis, with the strongest effect for non-infectious uveitis (0.0067, 95% CI 0.0041 to 0.013).

“There were positively significant associations between temperature and uveitis for each province. The strength of temperature–uveitis association ranged from 0.0011 to 0.072 (95% CI ranged 0.00037 to 0.10) in provinces of mainland China. Furthermore, we found that the association between temperature and uveitis became stronger in the course of our study period,” according to the investigators.

Also, the results indicated that risks from abnormal temperature exposure are higher for male individuals and people between 20 years and 50 years old than for other groups.

Prior to this study, environmental influences on uveitis have not been extensively studied, though they have been implicated in the development of uveitis.

 While “some uveitis subtypes and related inflammatory factors have certain seasonal patterns,” the investigators report “no studies have determined whether the patterns are caused by seasonally varying temperatures, or by other seasonally varying climatic factors (such as precipitation, humidity, and sunlight). It is important to determine whether uveitis is associated with climate, because it helps us understand this disease burden brought by changes in climate.” 

The study, the largest to ever investigate the association between uveitis and climate, was focused on China because the country both has the largest population in the world and is the largest emitter of greenhouse gases, according to the research. 

The study is limited in that, while a clear association between temperature and the onset of uveitis exists, the specific mechanisms behind that association remain unclear. Also, since the climate data came from China, the findings of this study may only be most relevant for areas with similar climate and infrastructure. 

The investigators are hopeful that their study will help create more awareness around the disease caused by global warming and aid in implemented policies to mitigate future temperature increases. 

Tan H, Pan S, Zhong Z, et al., Association between temperature changes and uveitis onset in mainland China. Br J Ophthalmol. Published online October 14, 2020. doi:10.1136/bjophthalmol-2020-317007