Past or Current Smoking Predicts End-Organ Damage in Systemic Lupus Erythematosus

The onset of end-organ damage in patients with systemic lupus erythematosus (SLE) may be 4 to 5 years earlier in current or former smokers compared with never smokers, according to study results published in Lupus. Current smokers and smokers with a pack-year history of greater than 10 years accumulated damage twice the rate as that of never smokers.

Although there is some evidence that smoking increases the risk of developing SLE, the relationship between smoking and SLE has not been well studied.

In the current retrospective cohort study, the researchers sought to investigate the effect of smoking history and pack-year exposure on accumulated damage in patients with SLE.

Researchers assessed the clinical records of patients with incident SLE between 2003 and 2016 for smoking status, cumulative smoking exposure, sociodemographics, and comorbidities. Primary outcomes were the time to onset of end-organ damage, measured using the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SLICC/ACR-DI), or death.

Sociodemographic data revealed that a greater percentage of Black patients and those receiving Medicaid were current smokers (P for both <.05). Former smokers vs current or never smokers were found to be older (mean age, 51.7 years vs 41.7 and 44.3 years, respectively) and more frequently had late-onset SLE (54% vs 29% and 33%, respectively). 

Using unadjusted Kaplan-Meier survival analysis, the researchers found that the median time to SLICC/ACR-DI increase or death in never smokers was 9.0 years compared to 3.4 years in former smokers and 4.5 years in current smokers (P =.002).

In multivariate Cox proportional hazards models, current smokers had 2.2 times the rate of damage increase or death compared with that of never smokers (hazard ratio [HR], 2.18; 95% CI, 1.33-3.57). A stepwise increase in hazard rates was also noted with increasing pack-years. Current smokers and smokers with 5 to 10 pack-years had 1.6 times higher rate of damage accrual or death than that of never smokers (HR, 1.55; 95% CI, 0.86-2.80); with greater than10 pack-years, the rate increased to 2.4 (HR, 2.35; 95% CI, 1.15-3.64).

Study limitations included the cohort was different in age, race, ethnicity, and smoking behavior than the United States population of patients with SLE; data on medications that might affect SLE was not collected; disease activity was not included in the modeling; patient-reported pack-years was used, as opposed to standardized daily or lifetime cigarettes smoked; and patients were not assessed for antiphospholipid antibody syndrome.

Researchers concluded, “Further work should examine the impacts of smoking and smoking cessation on end-organ damage in a prospective fashion, and in a more diverse population. Smoking cessation may represent an important strategy for reducing morbidity due to end-organ damage in lupus.”

Disclosure: One study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of the author’s disclosures.

Reference

McKown T, Schletzbaum M, Unnithan R, Wang X, Ezeh N, Bartels C. The effect of smoking on cumulative damage in systemic lupus erythematosus: An incident cohort study. Lupus. Published online January 20, 2021. doi:10.1177/0961203320988603