Goals, cheers, and gamma-GT: Do football tournaments affect laboratory parameters?

Background Major international football tournaments are mass gathering events associated with increased alcohol consumption, emotional stress, and healthcare utilization. While acute health effects have been described in emergency settings, their impact on routine laboratory parameters at the population level remains unclear. Methods We conducted a retrospective analysis of 564,316 laboratory measurements obtained within predefined observation windows surrounding 19 UEFA European Championships and FIFA World Cups (2004–2023) at a large tertiary care center. Event periods (tournament days) were compared with temporally adjacent reference periods. Primary outcomes included liver-related parameters (ALAT, ASAT, GGT), with secondary analyses of inflammatory markers (CRP, WBC) and exploratory assessment of pancreatic enzymes. Outcomes were evaluated as proportions above the upper limit of normal (ULN) and distributional measures. Statistical comparisons were performed using χ 2 and Wilcoxon rank-sum tests, with false discovery rate correction applied as a sensitivity analysis. Results Proportions of values exceeding the ULN were comparable between event and reference periods for ALAT (15.9% vs. 16.3%, p < 0.001), ASAT (11.4% vs. 11.7%, p = 0.031), and GGT (26.3% vs. 27.0%, p < 0.001), with only minimal absolute differences. CRP was slightly lower during event periods (40.1% vs. 41.0%, p < 0.001), while WBC showed no difference (24.4% vs. 24.4%, p = 0.93). Distributional analyses demonstrated largely overlapping patterns without systematic shifts. No consistent effects were observed across tournament context, including time zone differences, match relevance, or tournament phase. False discovery rate correction did not materially alter the interpretation of the findings. Conclusion Despite strong behavioral and biological plausibility, major football tournaments were not associated with clinically meaningful changes in routine laboratory parameters at the population level. These findings reveal population-level buffering of event-related behavioral effects in routine laboratory data, demonstrating methodological limits of opportunistic surveillance for subtle mass gathering impacts and highlighting epidemiological resilience to transient exposures.