High or moderate personal exposure to intense environmental ultraviolet radiation has been linked to the development of dermatomyositis, compared with other types of myositis, according to research results published in Arthritis Care & Research.
Researchers sought to determine the role of individual determinants of ultraviolet exposure before dermatomyositis diagnosis. They evaluated whether differences in sunburn and personal sun exposure in the year prior to dermatomyositis diagnosis were associated with the condition. Data were collected from a national registry of myositis patients in the United States between 2010 and 2012.
Participants (n=9211) were sent a questionnaire that collected demographic data, disease-related information, environmental exposures, and questions about work and hobbies. In total, 22% of participants (n=1956) returned the completed questionnaire, and 1806 met either probable or definite Bohan and Peter criteria for dermatomyositis or polymyositis or the Griggs’ criteria for possible inclusion body myositis.
Overall, study respondents who reported sunburn were younger, regardless of idiopathic inflammatory myopathy phenotype. Sunburn was more common in women with dermatomyositis; participants who reported sunburn were more likely to report having a fair skin tone and a tendency to experience severe sunburn, regardless of idiopathic inflammatory myopathy phenotype.
Compared with 28% of patients with polymyositis or inclusion body myositis, 42% with dermatomyositis reported sunburn in the year prior to diagnosis. Investigators found that the association was “somewhat stronger” for those reporting 2 or more sunburns (odds ratio [OR], 1.77; 95% CI, 1.28-2.43; P =.0005), but was both elevated and statistically significant for 1 sunburn (OR, 1.44; 95% CI, 1.06-1.95; P =.018). Data from adjusted models indicated an elevated but not statistically significant association between dermatomyositis and high or moderate level occupational sun exposure (OR, 1.36; 95% CI, 0.96-1.93) compared with low or no exposure. However, recreational sun exposure was common (67% of study patients with dermatomyositis) and significantly associated with dermatomyositis (OR, 1.34; 95% CI, 1.05-1.73).
Sex-based differences in the dermatomyositis phenotype were not statistically significant, but there was a more apparent association of dermatomyositis with sunburn history in women with 2 or more sunburns (OR, 1.98; 95% CI, 1.36-2.89) vs those with none; occupational sun exposure was associated with dermatomyositis primarily in men (OR, 1.70; 95% CI, 1.00-2.90).
No overall difference was noted when comparing the prevalence of sunburn reported in the year prior to diagnosis in registry participants with population rates gathered from the Behavioral Risk Factor Surveillance System, however, women with dermatomyositis had a higher age-adjusted prevalence of sunburn compared with women in the survey population (30.7% vs 23.5%; P =.015).
Study limitations included the use of a volunteer-based registry, which may not accurately reflect the number of idiopathic inflammatory myopathy cases in the general population, and the use of self-reported data. Findings could also have been subject to exposure misclassification bias.
“Our findings provide preliminary evidence that an individual’s exposures to [ultraviolet] radiation through job- and hobby-related sun exposures may influence the risk of developing [dermatomyositis],” the researchers concluded. “Further research is needed on the role of individual susceptibility and sun [protective behaviors in the risk of [dermatomyositis], and to compare patients [with dermatomyositis] with [a control group].”
Parks CG, Wilkerson J, Rose KM, et al. Association of ultraviolet radiation exposure with dermatomyositis in a national myositis patient registry [published online September 3, 2019]. Arthritis Care Res. doi:10.1002/acr.24059