UCSF

Background

Higher urine albumin-creatinine ratio (ACR) is associated with cardiovascular disease (CVD) events, an association that is stronger than that between spot urine albumin on its own and CVD. Urine creatinine excretion is correlated with muscle mass, and low muscle mass also is associated with CVD. Whether low urine creatinine concentration in the denominator of the ACR contributes to the association of ACR with CVD is uncertain.

Study design

Prospective cohort study.

Setting & participants

6,770 community-living individuals without CVD.

Predictors

Spot urine albumin concentration, the reciprocal of the urine creatinine concentration (1/UCr), and ACR.

Outcome

Incident CVD events.

Results

During a mean of 7.1 years of follow-up, 281 CVD events occurred. Geometric mean values for spot urine creatinine concentration, urine albumin concentration, and ACR were 95 ± 2 (SD) mg/dL, 0.7 ± 3.7 mg/dL, and 7.0 ± 3.1 mg/g. Urine creatinine concentration was lower in older, female, and low-weight individuals. Adjusted HRs per 2-fold higher increment in each urinary measure with CVD events were similar (1/UCr: 1.07 [95% CI, 0.94-1.22]; urine albumin concentration: 1.08 [95% CI, 1.01-1.14]; and ACR: 1.11 [95% CI, 1.04-1.18]). ACR ≥10 mg/g was associated more strongly with CVD events in individuals with low weight (HR for lowest vs highest tertile: 4.34 vs 1.97; P for interaction = 0.006). Low weight also modified the association of urine albumin concentration with CVD (P for interaction = 0.06), but 1/UCr did not (P for interaction = 0.9).

Limitations

We lacked 24-hour urine data.

Conclusions

Although ACR is associated more strongly with CVD events in persons with low body weight, this association is not driven by differences in spot urine creatinine concentration. Overall, the associations of ACR with CVD events appear to be driven primarily by urine albumin concentration and less by urine creatinine concentration.