Cigarette smoking and systemic lupus erythematosus: a smoking gun?

Cigarette smoking is one of many environmental exposures, including infectious agents, silica exposure, hormonal and dietary factors, hypothesized to be linked to the development of SLE. Cigarette smoke contains hundreds of potentially toxic components, including tars, nicotine, carbon monoxide, polycyclic aromatic hydrocarbons among others. Whether cigarette smoking increases the risk of developing SLE remains controversial. To date, three case-control studies have reported significantly increased odds ratios for the development of SLE in smokers, while six others have not found a clear association. A meta-analysis statistically combining the effect estimates from the available studies, revealed a modestly increased risk posed by current smoking (RR 1.5 [95% CI 1.09, 2.08]), but no increased risk associated with past smoking. The strengths and weaknesses of these data and potential implications are discussed.