Two cardiovascular risk factors in one? Homocysteine and its relation to glomerular filtration rate: A meta-analysis of 41 studies with 27,000 participants

Background: Hyperhomocysteinemia is thought to be an independent risk factor for cardiovascular disease, but the association between renal dysfunction and homocysteine may not have been fully taken into account. We performed a meta-analysis of studies that report correlations between glomerular filtration rate (GFR) and homocysteine plasma levels. Methods: Using a prespecified research strategy, we identified 41 studies involving 26,617 participants that reported Pearson or Spearman correlation coefficients for the association between 1/GFR and homocysteine. The summary correlation coefficients with 95% CI were obtained by pooling the logarithmic Z values derived from the individual trial correlation coefficients. Subgroup analysis was performed to compare results for measured GFR using clearance methods and various estimates of GFR. Results: The pooled correlation coefficient between homocysteine and 1/GFR was 0.37 (CI 0.32-0.40, p < 0.0001). The correlation coefficient based on various estimates of GFR was 0.33 (CI 0.29-0.38, p < 0.0001), and for measured GFR it was 0.45 (CI 0.39-0.51, p < 0.0001). The correlation coefficient was higher when GFR was measured using clearance methods compared with various estimates GFR (1.36 [CI 1.13-1.65], p = 0.0014). Conclusions: Homocysteine plasma levels significantly depend on renal function. This correlation is even more robust when GFR is measured using clearance methods. Therefore, in order to assess whether homocysteine is an independent cardiovascular risk factor, accurate adjustments for renal dysfunction are essential.