Circulating bilirubin level is determined by both erythrocyte amounts and the proportion of aged erythrocytes in ageing and cardiovascular diseases.

BACKGROUND

Bilirubin has been involved in the process of ageing and the pathology of ageing-related diseases. Circulating bilirubin is mainly derived from the clearance of disintegrated erythrocytes in the blood. However, the change of serum bilirubin level and its regulation during ageing and in ageing-related diseases remain to be elucidated.

METHODS

A retrospective study was conducted by analyzing the blood cell test results and liver function results of 14,049 healthy research subjects at the Physical Examination Center and 2052 patients with various types of cardiovascular diseases (CVD) at the Department of Cardiology in Renmin Hospital of Wuhan University. Spearman correlation analysis and linear-regression analysis were used for correlation studies. Differences between male and female were investigated.

RESULTS

Whereas the erythrocyte counts continuously decreased along with age, the proportion of aged erythrocytes was significantly increased in both male and female. The level of total circulating bilirubin was positively correlated with age and erythrocyte counts. The increase of bilirubin was associated with the increased morphological deviation of erythrocytes during ageing. Compared with health controls, the level of circulating bilirubin in CVD patients was significantly decreased consistent with the decline of erythrocyte counts and hemoglobin.

CONCLUSIONS

Ageing may be accompanied by an increased ageing rate of erythrocytes, which contributes to the ageing-related decline of erythrocyte counts. Both erythrocyte counts and the proportion of aged erythrocytes coordinately might determine the circulating level of bilirubin during ageing. In CVD, the decline of circulating bilirubin may be largely attributed to concurrent anemia.