In those who had cognitive impairment, N-glycopeptides with sialylated tri- or tetra-antennary glycans on alpha-2-macroglobulin, clusterin, serum paraoxonase/arylesterase 1, and haptoglobin were less abundant, whereas 3-sialylated tri-antennary N-glycopeptiforms on serotransferrin were more abundant. The gene discussed is A2M; the disease is Cognitive impairment.