Table 2.

The DSST z-scores and their corresponding 95% confidence intervals were stratified by quartiles of serum Cystatin C levels.

	Quartile 1 ≤ 0.786 mg/dl (n = 1,214)	Quartile 2 0.786–0.903 mg/dl (n = 1,204)	Quartile 3 0.903–1.07 mg/dl (n = 1,220)	Quartile 4 > 1.07 mg/dl (n = 1,194)
Digit symbol substitution test	0.16 (0.10,0.22)	0.18 (0.12,0.23)	−0.05 (−0.11,0.004)	−0.30 (−0.35,-0.25)