Meteorological conditions associated with vasovagal reactions in blood donors: A multicenter retrospective observational study

BACKGROUND: We previously reported that meteorological conditions were associated with blood donation-related vasovagal reactions (VVRs) at one facility. To assess generalizability across diverse climate zones and donation types, we conducted a multicenter study in eight Japanese regions. STUDY DESIGN AND METHODS: This retrospective multicenter study analyzed three-year data from eight regions (total donors: 2,915,272; VVR cases: 19,982). Meteorological variables were categorized into region-specific quartiles (Q1-Q4). Linear trends in VVR incidence across quartiles were evaluated using the Cochran-Armitage trend test; pairwise differences were assessed by Chi-squared tests with Bonferroni correction. Pooled odds ratios (ORs) for VVRs were estimated by logistic regression with region as a covariate (Q4 as reference). RESULTS: A divergent pattern emerged by donation type. In fixed-site apheresis, significant inverse trends between temperature and VVR incidence were observed across all seven regions for 7-day weighted moving averages. Minimum temperature showed the strongest association: pooled ORs for Q3, Q2, and Q1 were 1.27 (95% confidence interval [CI] 1.21-1.33), 1.41 (1.35-1.48), and 1.51 (1.45-1.58) (all p < 0.001). No consistent association was found for fixed-site whole blood donors (minimum temperature Q1: OR 1.06; p = 0.064). In mobile collections, lower temperature was associated with reduced VVR risk (mean temperature Q1: OR 0.87; p = 0.003), while intermediate quartiles showed increased risk, a pattern distinct from fixed-site apheresis. CONCLUSION: Low temperature was associated with VVR in fixed-site apheresis across diverse climates, consistent with acute indoor-outdoor transitions and sustained cold exposure. Mobile collections showed a different pattern, warranting donation-type-specific approaches to meteorological risk management.