Relationship of regional ultraviolet index data with rash and systemic disease activity in youth with childhood-onset systemic lupus: results from the Childhood Arthritis and Rheumatology Research Alliance Registry.

Objective: To investigate the association between ultraviolet light index (UVI), as a marker for UV exposure, and seasonality with rash and systemic disease activity in youth with childhood-onset systemic lupus (cSLE) from the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry.

Methods: We reviewed data on rash and disease activity from Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2 K) scores from cSLE CARRA Registry participants with visits between 2010 and 2019 and obtained zipcode level UVI data from the National Oceanic and Atmospheric Administration (NOAA). Our main exposures were UVI and season during the month of visit and one month prior to visit. We used mixed-effects logistic regression models to examine associations between regional UVI (by zipcode)/season and odds of rash and severe SLEDAI-2 K score (≥ 5 vs. 0-4), adjusting for age, sex, race and income.

Results: Among 1222 participants, with a mean of 2.3 visits per participant, 437 visits (15%) had rash and 860 (30%) had SLEDAI-2 K score ≥ 5. There were no associations between UVI during the month prior to visit or the month of the visit and odds of rash or elevated systemic activity. However, fall season was associated with increased odds of rash (OR = 1.59, p = 0.04), but not increased disease activity.

Conclusion: This study found no association between UVI and rash or UVI and disease activity. However, further studies directly measuring UV exposure and accounting for patient-level protective behavioral measures may help to better understand the complex relationship between sun exposure and SLE disease activity.