Independent Association Between Occupational Exposure and Decline of FVC in Systemic Sclerosis: A Multicenter Recruitment Retrospective Cohort Study

Abstract

Background: Although male sex is associated with poor prognosis in systemic sclerosis (SSc), it is unclear whether this association is independent of confounding factors such as occupational exposure to toxicants.

Research question: What is the respective impact of sex and occupational exposure on characteristics of patients with SSc with a focus on lung function decline?

Study design and methods: Patients with SSc (n = 210; 55 men) underwent standardized quantitative assessment of occupational exposure through a cumulative exposure score (CES) in a multicenter recruitment retrospective cohort. Association of the CES with patients' characteristics was assessed. Mixed linear, logistic, and Cox regression models were used to identify predictors of time variation of FVC and the diffusing capacity of the lungs for CO₂ corrected for hemoglobin (Dlcoc).

Results: Male sex was associated strongly with occupational exposure (OR, 10.3; P < .0001). The CES was correlated inversely (r = -0.20) and associated independently with decline in FVC over time and with occurrence of FVC decline of ≥ 10% from baseline (P < .05). By contrast, the CES was not associated with decline in Dlcoc or Dlcoc decline of ≥ 15%. No independent association was found between sex and decline in FVC or Dlcoc. The prevalence of interstitial lung disease was similar across sex or occupational exposure.

Interpretation: Occupational exposure to toxicants seems to predict decline of FVC in patients with SSc independently, regardless of sex. Assessment of occupational exposure may be useful for SSc prognostication.

Keywords: FVC variation; occupational exposure; sex; systemic sclerosis.