Cox regression analyses showed that serum bicarbonate level had inverse associations with incident ESRD ( HR , 0.91 ; 95 % CI , 0.89-0 .93 ; P < 0.001 ) and incidence of the combined end point of ESRD or serum creatinine doubling ( HR , 0.94 ; 95 % CI , 0.92-0 .96 ; P < 0.001 ) .