Background/Purpose: Multiple variables are known to contribute to development of organ damage in SLE patients, including prednisone use and ethnicity. The aim of this study was to evaluate the attributable risk due to comorbidities (hypertension, obesity, smoking), and socioeconomic factors on the total SLICC/ACR Damage Index (DI) and its sub-items in a large longitudinal prospective SLE cohort.

Methods: We analyzed data from a longitudinal cohort of 2,436 SLE patients who met the revised ACR or SLICC classification criteria (43% African-American, 57% Caucasian and 92% female). The SLICC/ACR DI was calculated based on organ damage that occurred after the diagnosis with SLE until the last visit. The outcome variable was the total damage score and that of each organ system at the last available cohort visit. We calculated the population attributable risk (PAR) for the total and each organ damage. Person month files since SLE diagnosis were created. At each month, variables were created to identify if patients had damage accrual. We analyzed the data using pooled logistic regression where the outcome was binary for each organ (accrual of damage). To account for the fact that some patients could contribute multiple damage events in the analysis, the GEE approach was used in fitting the model. Each model was adjusted for sex and age at the person month. Regression coefficients from the model were then used to calculate PAR.

Results: The mean total SLICC/ACR DI was 1.9 (SD=2.3). Hypertension was the strongest contributor to damage accrual, after adjusting for age and sex (Table 1 and 2). Hypertension was responsible for 30% of total damage: 70% of renal damage and 40% of cardiovascular damage was attributed to hypertension. The importance of hypertension was true regardless of ethnicity. Obesity was a strong contributor to neuro-psychiatric (23%) and renal (15.4) damage in Caucasians. It played a less important role in African-American patients, contributing only 3% and 0.8% to neuro-psychiatric and renal damage, respectively. Obesity was protective against skin damage in both African-Americans and Caucasians. Smoking contributed mostly to cardiovascular (13%) and skin (32%) damage. (Table 1). Only about 10% of any organ damage was accounted for by socioeconomic status. The 3 socioeconomic measures, education, low income, and insurance, contributed equally to total damage in patients with SLE. Socioeconomic status played a greater role in skin (28.3%) and peripheral vascular damage (21.5%), compared to damage in the other organ systems (Table 2).

Conclusion: Of the three comorbidities, hypertension had the highest PAR for total, renal and cardiovascular damage, regardless of ethnicity.  Obesity had a protective effect for skin damage.  The three measures of socioeconomic status were less important than hypertension.  Low income appeared to attribute more PAR than education or type of insurance.  The Eight Americas Study found that ethnicity, rather than socioeconomic status, explained the ethnic differences in mortality.  Our study suggests that ethnicity and hypertension are the most important contributors to organ damage (the strongest predictor of mortality).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/organ-damage-in-systemic-lupus-erythematosus-is-attributable-more-to-comorbidity-hypertension-and-less-to-socioeconomic-status/