Relationship between Serum Uric Acid and Mortality Risk in Hemodialysis Patients: A Multicenter Prospective Cohort Study

BACKGROUND

Several studies have reported that low serum uric acid (SUA) levels are related to increased risk of mortality in maintenance hemodialysis (MHD) patients. However, the possible detrimental effects of high SUA on the mortality risk have not been well examined. Moreover, the possible effect modifiers for the SUA-mortality association have not been fully investigated. To address the aforementioned gap, we aimed to explore the nonlinear relationship between SUA levels and all-cause and cardiovascular disease (CVD) mortality risk, and to examine any possible effect modifiers in MHD patients.

METHODS

We conducted a multicenter, prospective cohort study among 1,018 MHD patients from 8 hemodialysis centers. The primary outcome was all-cause mortality, and the secondary outcomes were CVD mortality and non-CVD mortality.

RESULTS

The mean value for SUA in the total population was 8.5 ± 1.9 mg/dL. The lowest and highest quintiles of SUA were <7.0 and >10.1 mg/dL, respectively. Over a median follow-up of 45.6 months, 343 deaths were recorded, of which 202 (58.9%) were due to CVD. When SUA was assessed as quintiles, a significantly higher risk of all-cause mortality was found in patients in quintile 1 (<7.0 mg/dL; hazard ratio [HR], 1.33; 95% confidence interval [CI]: 1.02-1.73) or quintile 5 (≥10.1 mg/dL; HR, 1.47; 95% CI: 1.09-2.00), compared to those in quintiles 2-4 (7-10.1 mg/dL). Moreover, the U-shaped SUA-mortality association was mainly found in those with lower C-reactive protein levels (<3 compared with ≥3 mg/L; p for interaction = 0.018). Similar trends were found for CVD mortality and non-CVD mortality.

CONCLUSION

There was a U-shaped relationship between SUA levels and the risk of all-cause mortality, CVD mortality, and non-CVD mortality in MHD patients.

Baseline Serum Magnesium Level and Its Variability in Maintenance Hemodialysis Patients: Associations with Mortality

BACKGROUND/AIMS

The study aimed at investigating the impact of serum magnesium (Mg) baseline level and its variability on mortality in maintenance hemodialysis (MHD) patients.

METHODS

Eligible patients receiving regular MHD at Ningbo No. 2 Hospital between January 2009 and August 2016 were enrolled and follow-ups were conducted afterwards until death or transplantation. General information, laboratory results, and outcomes of subjects were collected. The relationship between baseline serum Mg level, its coefficient of variation (CV), and all-cause mortality and cardiovascular disease mortality were assessed, respectively. Subjects were divided into groups in 2 manners: by serum Mg level (lower Mg group: serum Mg <1.00 mmol/L, higher Mg group: serum Mg ≥1.00 mmol/L) and by serum Mg CV (high variation group: CV ≥0.149 mmol/L, middle variation group: 0.114 mmol/L ≤ CV < 0.149 mmol/L, and low variation group: CV <0.114 mmol/L).

RESULTS

169 MHD patients were recruited in the study, with mean serum Mg 1.00 ± 0.18 mmol/L, average age 60.20 ± 15.64 years, and median dialysis duration 37.00 (18.30, 77.97) months. During the follow-up, 69 (40.83%) patients died, 24 (34.78%) of which died due to cardiovascular disease. Comparing the two groups, patients in the lower Mg group had a higher all-cause mortality (50.00 vs. 29.33%, p = 0.007). The multivariate Cox regression analysis suggested that lower Mg level was an independent factor for all-cause mortality as well as cardiovascular mortality (HR = 13.268, 95% CI 6.234-28.237, p < 0.001; HR = 12.702, 95% CI 3.737-43.174, p < 0.001, respectively). However, there were no significant statistical differences of all-cause and cardiovascular mortality among these three groups concerning Mg variation. And in the univariate and multivariate Cox regression analysis, serum magnesium CV was not the independent factor for all-cause mortality and cardiovascular mortality.

CONCLUSIONS

The lower baseline serum magnesium level was associated with all-cause and cardiovascular mortality in MHD patients. However, the variability of magnesium level was not independently associated with the risk of death and further studies need to be conducted.

The presence and impact of diastolic dysfunction on physical function and body composition in hemodialysis patients

BACKGROUND

Cardiovascular (CV) diseases are the main cause of death in maintenance hemodialysis (MHD) patients. Muscle wasting and physical function decline are common in MHD patients, and significantly impair their quality of life. These can result from abnormalities in cardiac function, which can be further worsened by physical deconditioning. Left ventricular diastolic function parameters were recently shown to be a better predictor of exercise capacity than systolic measures in patients with CV complications. But little is known about the relationship between cardiac function and physical function in MHD patients.

METHODS

In 82 MHD patients, left ventricular systolic dysfunction (LVSD) was assessed by ejection fraction and fractional shortening with echocardiography, and left ventricular diastolic dysfunction (LVDD) was assessed by pulse wave and tissue Doppler indices. Physical function was assessed by gait speed, performance on a shuttle walk test, and leg muscle strength. Dual-emission X-ray absorptiometry (DXA) was used to measure whole body lean mass (WBLM).

RESULTS

The prevalence of LVDD and LVSD was 48.8 and 12.2%, respectively. Gait speed, shuttle walk time, leg strength, and WBLM% were significantly higher in the group without LVDD than with LVDD (p < 0.05 for all). However, there was no significant difference in any measure of physical function or body composition between patients with and without LVSD.

CONCLUSION

These data suggest that LVDD is more closely related to physical function and body composition than LVSD in MHD patients, and hence that LVDD may be an important therapeutic target.