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.