Smoking exposure in pack-years predicts cutaneous manifestations and damage in systemic lupus erythematosus.

Objective: To examine the impact of cumulative smoking in pack-years on systemic lupus erythematosus (SLE) cutaneous manifestations and damage.

Methods: Our cohort study included 632 adult SLE patients at an academic center, meeting 1997 ACR or 2012 SLICC classification criteria. Outcomes were: (1) cutaneous SLICC Damage Index (SDI), (2) ACR and SLICC criteria. Smoking exposure was defined as low (<5 pack-years), medium (5-10), and high (>10), compared to non-smokers. Analysis used multivariable logistic regression to calculate odds ratios and confidence intervals (OR, (95% CI)).

Results: Among 632 SLE patients, mean age 42 ± 14, 91% were female, 82% White, and 40% were ever smokers. Black patients were more likely to have smoked (51% vs. 41% White, 11% Other). Chronic SLICC and SDI cutaneous criteria showed linear pack-year trends, meeting significance with high smoking exposure (OR 2.2, (1.2, 4.2); OR 4.2, (1.9, 9.2)). Those with medium exposure were more likely to meet acute SLICC cutaneous criteria (OR 2.3, (1.1, 5.1)). Low exposure predicted any cutaneous SLICC and ACR criteria (OR 3.7, (1.3, 10.6); OR 2.0 (1.03, 3.8)). Patients of color had more chronic SLICC cutaneous criteria (Other Race OR 3.6 (1.6, 8.1)) and SDI skin damage (Black OR 2.6 (1.1, 5.9)) even controlling for smoking exposure.

Conclusions: Smoking was an independent risk factor for cutaneous SLE. High pack-year exposure and non-White race increased chronic skin manifestations and SDI damage. Findings suggested a dose relationship between smoking and cutaneous SLE damage, making cessation messaging important to potentially improve outcomes and reduce some disparities.