Higher risk of upper respiratory tract infection post marathon running: when physical exercise becomes a threat to the immune system.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of non-controlled pre-post observational studies
What was done
Authors conducted a systematic review and meta-analysis across six databases (MEDLINE, Embase, Scopus, Web of Science, Cochrane Library, EBSCOhost) up to December 1, 2022. They included 7 non-controlled intervention studies tracking upper respiratory tract infection (URTI) symptoms for 1 to 4 weeks before and after marathon running. Pre-marathon infection rates were mathematically adjusted to account for unequal pre- and post-race follow-up durations.
What was found
Post-marathon running was associated with an 18% higher incidence of URTI compared to pre-marathon baseline (OR 1.18, 95% CI [1.05 to 1.33], p = 0.005) across 7 included studies. Between-study heterogeneity was low (I² = 0%, p = 0.69) with no significant publication bias (Egger test p = 0.82). The authors assessed the overall quality of evidence as moderate using GRADE.
Why it matters
By adjusting for disparate pre- and post-race observation windows, this meta-analysis provides consolidated evidence of a modest but statistically significant elevation in acute respiratory infection risk following marathon completion.
Limits
The abstract does not state the total participant sample size. All included studies were non-controlled pre-post designs relying on subjective reporting of symptoms without laboratory pathogen confirmation, and required post-hoc mathematical adjustments to harmonize differing follow-up times.
Cited by
- supports Endurance athletes training for marathons have a higher incidence of upper respiratory tract infections.