Association between influenza infection and subsequent Parkinson's disease diagnosis: a systematic review and meta-analysis.

Abstract

Introduction: As infectious agents may be associated with neurodegenerative diseases, this systematic review and meta-analysis investigated whether prior influenza infection is associated with an increased odds of subsequent Parkinson's disease (PD) diagnosis.

Methods: We searched PubMed, Web of Science, and Scopus for observational studies examining influenza infection and later PD diagnosis. Seven studies (comprising eight cohorts) were analyzed using frequentist and Bayesian random-effects meta-analyses. Meta-regression and subgroup analyses were conducted to explore the moderating effect of the time interval between influenza exposure and subsequent PD diagnosis (i.e. exposure window).

Results: A significant association was observed in both approaches: pooled OR = 1.87 (95% CI: 1.24-2.81) under the frequentist model, and posterior median OR = 1.88 (95% CrI: 1.07-3.36) under the Bayesian model. Meta-regression and subgroup analyses identified the influenza exposure window as a moderator (R² = 36.6%, p < 0.05), with studies reporting influenza exposure within five years before PD diagnosis showing the strongest associations.

Conclusion: Our findings support a probable and temporally sensitive association between influenza infection and subsequent PD diagnosis. However, these findings should be interpreted cautiously, given the retrospective and heterogeneous nature of the available data.