Impact of microalbuminuria on incident stroke: a meta-analysis.

BACKGROUND AND PURPOSE Microalbuminuria, a marker of both kidney disease and endothelial dysfunction, may be associated with global vascular risk, but the nature and magnitude of the link between microalbuminuria and incident stroke has not been clearly defined. The purpose of this study was to assess the consistency and strength of the association of microalbuminuria with risk of stroke in prospective studies using meta-analysis. METHODS We conducted a systematic search of electronic databases and bibliographies for studies reporting a multivariate-adjusted estimate, represented as relative risk with 95% CI, of the association between microalbuminuria and stroke risk. Studies were excluded if a majority of study participants had established kidney disease or pre-eclampsia. Estimates were combined using a random-effect model. RESULTS We identified 12 studies, with a total of 48 596 participants and 1263 stroke events. Overall, presence of microalbuminuria was associated with greater stroke risk (relative risk, 1.92; 95% CI, 1.61 to 2.28; P < 0.001) after adjustment for established cardiovascular risk factors. There was evidence of significant heterogeneity in the magnitude of the association across studies (P for heterogeneity < 0.001, I² = 68%), which was partially explained by differences in study population, microalbuminuria definition, and different microalbuminuria-related risk among stroke subtypes. However, in stratified analyses, microalbuminuria was associated with increased risk of subsequent stroke in all subgroups (general population, diabetics, those with known stroke). CONCLUSIONS Microalbuminuria is strongly and independently associated with incident stroke risk. Future studies should explore whether microalbuminuria is just a risk marker or a modifiable risk factor for stroke.