Sympathetic nerve traffic overactivity in chronic kidney disease: a systematic review and meta-analysis.

BACKGROUND: Studies based on microneurographic sympathetic nerve activity (MSNA) recordings have shown that the sympathetic system is overactivated in chronic kidney disease (CKD) patients but the relationship between MSNA and renal function and other risk factors has not been systematically reviewed in this population. DESIGN AND MEASUREMENTS: This meta-analysis compares MSNA in cardiovascular complications-free CKD patients (n = 638) and healthy individuals (n = 372) and assesses the relationship of MSNA with the eGFR, age, BMI and hemodynamic variables. RESULTS: In a global analysis, MSNA was higher in CKD patients than in healthy control individuals (P < 0.001). The difference in MSNA between patients and healthy individuals was more marked in end-stage kidney diseases patients than in stage 3A 3B CKD patients (P < 0.001). In an analysis combining patients and healthy individuals, MSNA rose gradually across progressively lower eGFR categories (P < 0.01). In separate meta-regression analyses in CKD patients and in healthy individuals, MSNA associated directly with age (CKD: r = 0.57, P = 0.022; healthy individuals: r = 0.71, P = 0.031) and with the BMI (r = 0.75, P = 0.001 and r = 0.93, P = 0.003). In both groups, MSNA correlated with heart rate (r = 0.77, P = 0.02 and r = 0.66, P = 0.01) but was unrelated to plasma norepinephrine. CONCLUSION: Independently of comorbidities, MSNA is markedly increased in CKD patients as compared with healthy individuals and it is related to renal function, age, the BMI and heart rate. Sympathetic activation intensifies as CKD progresses toward kidney failure and such an intensification is paralleled by a progressive rise in heart rate but it is not reflected by plasma norepinephrine.