Plasma cystatin C is used to assess kidney function (Ferguson et al., 2015), and a higher level of cystatin C has been associated with increased risk of many age‐related traits, such as chronic obstructive pulmonary disease (COPD) and cardiovascular disease (CVD) (Lu, Quach, et al., 2019). The gene discussed is CST3; the disease is chronic obstructive pulmonary disease.