Nonobstructive chronic bronchitis ups risk of death among smokers

Patients with nonobstructive chronic bronchitis are at heightened risk of death, but this association is only present among current and former smokers, according to a systematic review and meta-analysis.

Researchers searched multiple online databases for studies that evaluated the relationship of nonobstructive chronic bronchitis and all-cause mortality. Studies that included participants with obstructive spirometry and studies that did not define chronic bronchitis and mortality were excluded.

The search yielded 5,014 titles, eight of which fulfilled the eligibility criteria. Study quality was assessed using the Newcastle-Ottawa Quality Assessment Scale, while visual inspection of a funnel plot was performed to identify publication bias.

Pooled data showed that nonobstructive chronic bronchitis carried a 37-percent increased risk of all-cause mortality (hazard ratio [HR], 1.37, 95 percent confidence interval [CI], 1.26–1.50) with no statistically significant heterogeneity (p=0.14, I², 29 percent).

The association between nonobstructive chronic bronchitis and elevated mortality was seen in studies that defined chronic bronchitis as any respiratory symptoms (broad definition; HR, 1.28, 95 percent CI, 1.10–1.48; I², 0 percent) as well as in the rest of the studies (HR, 1.40, 95 percent CI, 1.26–1.56; I², 37 percent).

Finally, the heightened risk of mortality associated with nonobstructive chronic bronchitis was especially pronounced among ever smokers (HR, 1.49, 95 percent CI, 1.35–1.64; I², 0 percent) but was absent among never smokers (HR, 1.22, 95 percent CI, 0.90–1.66).

There was moderate heterogeneity across studies (p=0.10, I², 49 percent). The funnel plot did not indicate any evidence of a publication bias.

Additional investigation is needed to determine whether early therapeutic intervention may benefit the high-risk population of nonobstructive chronic bronchitis patients.