Cigarette Smoke Exposure Linked to Increased Morbidity in SLE

Environmental factors are widely believed to influence systemic lupus erythematosus (SLE). Cigarette smoke is greatest significant source of environmental exposure to toxic chemicals and reactive molecular species, and numerous studies have shown that smoking cigarettes is a risk factor for increasing morbidity in SLE.¹

In order to better quantify and statistically analyze morbidity in patients with SLE, the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) Damage Index (SDI) was proposed and validated.² Assessment of cumulative chronic damage using the specific validated SDI score is one objective manner to quantify morbidity related to SLE.²

In a cross-sectional study by Montes and colleagues published in Arthritis & Rheumatology, 105 patients with SLE who visited the Hospital Universitário Antonio Pedro at Fluminense Federal University in Rio de Janeiro, between May 2013 and November 2014, were examined. ³

The main inclusion criteria were fulfillment of the SLICC criteria for SLE and regular treatment in the hospital outpatient unit for at least 6 months.  For the purposes of this study, exposure to tobacco smoke included active or secondhand smoking, current smoking, or previous smoking.

The study included 66 patients (62.9%) who did not meet any of the criteria for smoking exposure and 39 patients (37.1%) who had exposure of any kind. Within the exposed group, 28 patients (26.7%) were former smokers, 8 patients (7.6%) were current smokers, and 3 patients (2.9%) were exposed to secondhand smoker.

Of the 105 patients included, 74 patients had a positive SDI score ranging from 1 to 10 (SDI >0), and 31 patients had an SDI score of 0. Of the 74 patients with an SDI score >0, 42 patients had a “never exposed” status and 32 patients had an “ever exposed” status. The patients with an SDI score >0 made up 64% of the group with a “never exposed” status (42 of 66 patients) and 82% of the group with an “ever exposed” status (32 of 39 patients).

Analysis showed a 22% relative risk reduction of progression to a higher SDI score associated with never exposed status compared with patients who were ever exposed. A consecutive analysis using progressive values for cutoffs of SDI showed statistical significance at the cutoff level of SDI >0.  The risk remained statistically significant through SDI cutoff of > 1 (relative risk 0.65, P = .0348).

Summary and Clinical Applicability

Exposure to cigarette smoke is associated with increased morbidity in SLE as assessed by SDI score. It is also a potentially modifiable risk factor for chronic cumulative damage in SLE. Patients should be counseled against cigarette smoking and exposure, as it has been associated with more active SLE disease.

References

1. Costenbader KH, Kim DJ, Peerzada J, et al. Cigarette smoking and the risk of systemic lupus erythematosus: A meta-analysis. Arthritis Rheum. 2004 Mar;50(3):849-857.

2. Gladman DD, Urowitz MB, Goldsmith CH, et al. The reliability of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index in patients with systemic lupus erythematosus. Arthritis Rheum. 1997;40:809-813.

3. Montes RA, Morcarzel LO, Lanzieri PG, et al. Smoking and its association with morbidity in systemic lupus erythematosus evaluated by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index: preliminary data and systematic review. Arthritis Rheumatol. 2016 Feb;68(2):441-448. doi: 10.1002/art.39427.