GSTM1 and atrial fibrillation: Among individuals with Hb levels within normal ranges (13–15.9 g/dL in men and 12–14.9 g/dL in women), both decrease and increase in Hb levels at the second measurement outside the normal ranges showed an elevation of AF risk by 11% and 21% for men and 3% and 36% for women, respectively, compared with those who maintained normal Hb levels.