Influenza infection in patients with chronic obstructive pulmonary disease: a systematic review and meta-analysis of global prevalence and association with exacerbations

Influenza infection is a potential contributor to chronic obstructive pulmonary disease (COPD) morbidity, particularly during exacerbations. However, reported prevalence and its association with exacerbations vary across studies. A systematic review and meta-analysis were conducted to estimate the prevalence of influenza in COPD and exacerbated COPD patients and to evaluate its association with exacerbations. Random-effects models with logit transformation were used to pool prevalence estimates and odds ratios (ORs). Subgroup analyses were performed by influenza type and subtype, patient setting, data collection period, and geographic region. Heterogeneity and publication bias were assessed using standard methods. A total of 50 studies on COPD, 44 studies on exacerbated COPD, and 4 case-control studies were included. The pooled prevalence of influenza was 10.6% (95% CI: 8.2–13.3% and I² = 98.7% for overall COPD and 95% CI: 8.4–13.2% and I² = 93.7% for exacerbated COPD) in both COPD and exacerbated COPD populations. Influenza A was the predominant type, followed by influenza B and C. Among subtypes, H1N1 and H3N2 showed comparable prevalence. The pooled OR for the association between influenza and exacerbation of COPD was 1.08 (95% CI: 0.48–2.46), indicating no significant association. Subgroup analyses by patient setting, temporal analysis, and geographic region did not demonstrate statistically significant differences. The pooled estimates should therefore be interpreted as averages across heterogeneous settings rather than as universally applicable prevalence values. Evidence regarding an association with COPD exacerbation remains inconclusive.