A method for determining whether a subject is at risk of developing a circulatory disease; wherein the method comprises determining in a biological sample obtained from the subject a quantitative value of at least one biomarker of the following in the biological sample: - glycoprotein acetyls, - albumin, - a ratio of linoleic acid to total fatty acids, - a ratio of omega-6 fatty acids to total fatty acids, - a ratio of saturated fatty acids to total fatty acids, - fatty acid degree of unsaturation, - linoleic acid, - omega-6 fatty acids, - triglycerides in intermediate-density lipoprotein (IDL), - triglycerides in low-density lipoprotein (LDL), - acetate, - lactate, - pyruvate, - acetoacetate, - alanine, - glutamine, - glycine, - histidine, - phenylalanine, - tyrosine; and comparing the quantitative value(s) of the at least one biomarker to a control sample or to a control value; wherein an increase or a decrease in the quantitative value(s) of the at least one biomarker, when compared to the control sample or to the control value, is/are indicative of the subject having an increased risk of developing the circulatory disease; wherein the circulatory disease comprises or is atrial fibrillation and/or flutter; and wherein the at least one biomarker comprises or is glycoprotein acetyls, wherein glycoprotein acetyls refers to a nuclear magnetic resonance spectroscopy signal that represents the abundance of circulating glycated proteins. wherein the method comprises determining in a biological sample obtained from the subject a quantitative value of at least one biomarker of the following in the biological sample: - glycoprotein acetyls, - albumin, - a ratio of linoleic acid to total fatty acids, - a ratio of omega-6 fatty acids to total fatty acids, - a ratio of saturated fatty acids to total fatty acids, - fatty acid degree of unsaturation, - linoleic acid, - omega-6 fatty acids, - triglycerides in intermediate-density lipoprotein (IDL), - triglycerides in low-density lipoprotein (LDL), - acetate, - lactate, - pyruvate, - acetoacetate, - alanine, - glutamine, - glycine, - histidine, - phenylalanine, - tyrosine; and - glycoprotein acetyls, - albumin, - a ratio of linoleic acid to total fatty acids, - a ratio of omega-6 fatty acids to total fatty acids, - a ratio of saturated fatty acids to total fatty acids, - fatty acid degree of unsaturation, - linoleic acid, - omega-6 fatty acids, - triglycerides in intermediate-density lipoprotein (IDL), - triglycerides in low-density lipoprotein (LDL), - acetate, - lactate, - pyruvate, - acetoacetate, - alanine, - glutamine, - glycine, - histidine, - phenylalanine, - tyrosine; and comparing the quantitative value(s) of the at least one biomarker to a control sample or to a control value; wherein an increase or a decrease in the quantitative value(s) of the at least one biomarker, when compared to the control sample or to the control value, is/are indicative of the subject having an increased risk of developing the circulatory disease; wherein the circulatory disease comprises or is atrial fibrillation and/or flutter; and wherein the at least one biomarker comprises or is glycoprotein acetyls, wherein glycoprotein acetyls refers to a nuclear magnetic resonance spectroscopy signal that represents the abundance of circulating glycated proteins. <EOS>