The analysis of nadir Hb during SAH as a continuous variable showed stronger Hb decline in SAH individuals with cerebral vasospasm (∆ = 1.02 g/dL, 95% CI 0.69–1.35, p < 0.0001, I2 = 0%), cerebral infarction (∆ = 1.4 g/dL, 95% CI 1.1–1.7, p = 0.001, based on single study23), poor outcome at discharge (∆ = 1.3 g/dL, 95% CI 0.99–1.61, p < 0.0001, based on single study23) and follow-up (∆ = 1.31 g/dL, 95% CI 0.68–1.94, p < 0.0001, I2 = 89%) than in the comparison group without these complications. Here, GSTM1 is linked to brain infarction.