Association of Ultraviolet Radiation Exposure With Dermatomyositis in a National Myositis Patient Registry.

OBJECTIVE: Dermatomyositis (DM) has been associated with geospatial differences in ultraviolet (UV) radiation, but the role of individual determinants of UV exposure prior to diagnosis is unknown. The objective was to examine the role of those individual determinants. METHODS: We analyzed questionnaire data from 1,350 adults in a US national myositis registry (638 with DM, 422 with polymyositis [PM], and 290 with inclusion body myositis [IBM] diagnosed at ages 18-65 years), examining the likelihood of DM compared with PM and IBM diagnosis, in relation to self-reported sunburn history and job- and hobby-related sun exposures in the year prior to diagnosis. We estimated odds ratios (ORs) and 95% confidence intervals (95% CIs) using logistic regression adjusted for age, skin tone, and sex, to determine the association of individual UV exposures with DM diagnosis. We also evaluated the proportion of DM by maximum daily ambient UV exposure, based on UVB erythemal irradiances for participant residence in the year prior to diagnosis. RESULTS: DM was associated with sunburn in the year before diagnosis (2 or more sunburns OR 1.77 [95% CI 1.28-2.43] versus PM/IBM; 1 sunburn OR 1.44 [95% CI 1.06-1.95]) and with having elevated job- or hobby-related sun exposure (high exposure OR 1.64 [95% CI 1.08-2.49] or moderate exposure OR 1.35 [95% CI 1.02-1.78] versus low or no exposure). Ambient UV intensity was associated with DM in females (ß = 3.97, P = 0.046), but not overall. CONCLUSION: Our findings suggest that high or moderate personal exposure to intense sunlight is associated with developing DM compared with other types of myositis. Prospective research on UV exposure as a modifiable risk factor for DM is warranted.

Predictors of Reduced Health-Related Quality of Life in Adult Patients With Idiopathic Inflammatory Myopathies.

OBJECTIVE: Extensive studies on health-related quality of life (HRQoL) in idiopathic inflammatory myopathies (IIMs) are lacking. Our objective was to document HRQoL and to identify factors associated with a reduced HRQoL in patients with IIM. METHODS: A total of 1,715 patients (median age 49.9 years, 70% female, 87% white) who met probable or definite Bohan and Peter criteria or Griggs criteria for myositis were included from the Myovision registry. HRQoL was ascertained using the Short Form 12 (SF-12) health survey questionnaire. HRQoL physical component summary (PCS) and mental component summary (MCS) scores in relation to different patient and disease characteristics were compared to scores from matched normative data from the US general population and rheumatoid arthritis (RA) patients. Bivariate and multiple linear regression analyses were performed to assess the association between HRQoL and patient and disease parameters. RESULTS: The mean SF-12 summary scores were significantly lower in IIM patients than in the normative and RA populations. A diagnosis of inclusion body myositis, older age, patient-reported negative effect of disease on work, presence of another co-occurring autoimmune disease, polypharmacy, and IIM-associated lung disease and joint involvement were significantly associated with lower PCS scores. Lower MCS scores were associated with joint involvement and a negative effect of disease on work. CONCLUSION: In this large study of patient-reported outcomes in IIM, an association was found between multiple disease characteristics and reduced HRQoL, mostly in the physical domain. In the US, the HRQoL of IIM patients was found to be lower than that of the general population and RA patients.