Does smoking confound a GERD-IPF link?

  • Bédard Méthot D & al.
  • Chest
  • 1 Jan 2019

  • curated by Jenny Blair, MD
  • Clinical Essentials
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Takeaway

  • Gastroesophageal reflux disease (GERD) is associated with idiopathic pulmonary fibrosis (IPF), but the link disappears after adjustment for smoking.
  • Authors: “Our confidence in the estimate of association is low because it is exclusively from case-control studies…[which] are particularly susceptible to threats to internal validity through unmeasured confounders.”
  • Editorial calls meta-analysis “methodologically elegant,” adding, “when reported associations are weak…we confront the limits of observational epidemiology, making the leap from association to causation treacherous.” 

Why this matters

  • Existence of GERD-IPF causal link is debated.
  • IPF guidelines recommend antacid treatment.

Key results

  • All but 3 studies had higher proportions of smokers and ex-smokers among the IPF group.
  • GERD and IPF were associated: OR, 2.94 (95% CI, 1.95-4.42).
  • 1 study that adjusted for smoking as confounder linked IPF to:
    • Total reflux episodes: OR, 4.9 (P=.03); and 
    • Increased reflux exposure time: OR, 4.0 (P=.05).
  • Upon meta-regression taking smoking into account: OR, 0.66 (95% CI, 0.34-1.27).
  • No publication bias detected.

Study design

  • Systematic review and meta-analysis of 18 observational (all case-control) studies (3206 IPF patients and 9368 controls) probing links between GERD and IPF diagnoses.
  • Funding: None.

Limitations

  • GERD and IPF diagnostic criteria varied across studies.
  • Aggregate rather than individual data analyzed.

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