Low serum uric acid levels increase the risk of all-cause death and cardiovascular death in hemodialysis patients

Lower time-averaged serum uric acid was associated with increased mortality in peritoneal dialysis patients

BACKGROUND

The relationship between time-averaged serum uric acid (TA-SUA) levels and prognosis in peritoneal dialysis (PD) patients are rarely discussed.

METHODS

This was a retrospective cohort study. PD patients recruited from January 1, 2011, to December 31, 2020, were included. Baseline and follow-up uric acid levels over 1 year were collected to calculate time-averaged serum uric acid (TA-SUA) levels. Patients were divided into four groups based on TA-SUA quartiles: Q1 (<5.1 mg/dl), Q2 (5.1-5.8 mg/dl), Q3 (5.8-6.8 mg/dl), and Q4 (>6.8 mg/dl).

RESULTS

A total 487 PD patients with a mean age of 52.0 ± 14.2 were enrolled, including114 (23.4%) diabetes. Q1 (n = 121, 24.8%), Q2 (n = 118, 24.2%), Q3 (n = 125, 25.7%), and Q4 (n = 123, 25.3%). The Q1 group exhibited characteristics of increased age, malnutrition, and a higher prevalence of diabetes. During the 48.1 months follow-up time, 197 (35.8%) died, 109 (55.3%) cardiovascular disease (CVD), 38 (19.3%) infections. Kaplan-Meier analysis revealed that both all-cause mortality and cardiovascular mortality were significantly higher in the Q1 and Q4 groups (log-rank = 24.373, p < 0.001). COX regression analysis showed that decreased TA-SUA level was an independent risk factor for all-cause mortality in PD patients after adjustment for confounding factors. Each 1 mg/dl decrease in TA-SUA level was associated with a 23.46% increase in all-cause mortality (HR = 0.81, 95% CI, 0.71-0.94; p = 0.004*). Lower serum albumin level was associated with increased all-cause mortality.

CONCLUSION

PD patients with lower TA-SUA were older and had a higher proportion of diabetes and malnourishment than those with higher TA-SUA. Long-term exposure to low TA-SUA levels was an independent predictor of all-cause and cardiovascular mortality in PD patients.

Hyperuricemia prevalence and its risk factors in uremic patients undergoing maintenance hemodialysis

BACKGROUND

To explore the prevalence of hyperuricemia and its associated factors in uremic patients undergoing maintenance hemodialysis (MHD).

METHODS

Two hundred two uremic patients undergoing MHD for ≥ 3 months, in Jinshan Hospital, Fudan University, were enrolled. Pre-dialysis blood samples were tested during March 1st, 2023 to April 30th, 2023. Demographic characteristics were recorded. The prevalence of hyperuricemia, defined as serum uric acid (SUA) ≥ 420 μmol/L, was investigated. Individuals were divided into hyperuricemia (HUA) and non-hyperuricemia (n-HUA) groups. The demographic characteristics, residual kidney function, nutritional status, acid-base metabolism, electrolyte and lipid metabolism were compared between groups. The associated factors for hyperuricemia in MHD patients were identified by logistic regression.

RESULTS

The median SUA level of the enrolled patients was 458.50 (392.25, 510.75) μmol/L. 134 (66.34%) candidates met the diagnostic criteria of hyperuricemia. The median SUA level in HUA group was 491.00 (459.50, 543.50) μmol/L. Compared to those in n-HUA group, subjects in HUA group showed lower estimated glomerular filtration rate and blood CO2 level, but higher levels of body mass index, geriatric nutritional risk index, plasma phosphate, potassium, pre-albumin, albumin, serum creatinine (Scr) and urea nitrogen. Logistic regression indicated that Scr (OR 1.002, 95% CI 1.001-1.004, P = 0.003), albumin (OR 1.165, 95%CI 1.011-1.342, P = 0.035), and blood potassium (OR 1.673, 95% CI 1.009-2.773, P = 0.046) were associated factors for hyperuricemia in uremic patients undergoing MHD.

CONCLUSION

Hyperuricemia was highly prevalent among uremic MHD patients. Elevated levels of Scr, albumin and plasma potassium were independent associated factors for hyperuricemia.

Association between annual changes and visit-to-visit variability of serum uric acid and the kidney outcome in a general population

BACKGROUND

To determine whether variability of serum uric acid (UA) is associated with risk of chronic kidney disease (CKD) in a healthy population.

METHODS

Retrospective, longitudinal cohort study was conducted at a health examination center in China. The study enrolled subjects who had a minimum of three visits between 2011 and 2018. We assessed UA change and visit-to-visit UA variability including standard deviation (SD), coefficient of variation (CV), variability independent of the mean (VIM), and average real variability (ARV). Rapid estimated glomerular filtration rate (eGFR) decline was defined by annual eGFR change < -4 mL/min/1.73 m2/year. We conducted a multivariable-adjusted logistic regression analysis.

RESULTS

Ten thousand seven hundred and thirty-eight participants were included. During 4.43 ± 1.31 years follow-up, there were 535 cases with rapid eGFR decline and 240 cases developed CKD. Compared to the non-rapid eGFR decline group and non-CKD group, the UA annual changes and variability were higher in the rapid eGFR decline group and CKD group. The highest quartile of UA annual changes and variability showed a higher incident rate of rapid eGFR decline and that of CKD. After adjusting for covariates, OR for eGFR rapid decline in UA variability were 1.69 [1.53, 1.86] for annual changes of UA, 1.17 [1.08, 1.27] for SD of UA, 1.16 [1.06, 1.25] for CV of UA, 1.16 [1.07, 1.25] for VIM of UA, and 1.10 [1.02, 1.19] for ARV of UA. Consistent results were observed when CKD is used as the outcome.

CONCLUSIONS

Higher variability of serum UA was independently associated with the risk of kidney impairment.

The relationship between serum uric acid level and carotid intima-media thickness in hemodialysis patients

INTRODUCTION

We aimed to evaluate the relationship between carotid intima-media thickness (CIMT), which is a known indicator of cardiovascular risk and atherosclerosis, and uric acid level, which may be an easy marker for cardiovascular diseases due to its antioxidant and pro-oxidant properties in hemodialysis patients.

METHODS

In this cross-sectional study, we evaluated 77 hemodialysis patients. The mean CIMT of these patients was measured and recorded by Doppler ultrasonography. Patients were divided into two groups according to their serum uric acid levels. Correlation analysis and linear regression analysis were used to define the relationship between study parameters.

FINDINGS

The mean CIMT levels in the normouricemic group and the hyperuricemic group were 0.95 ± 0.15 and 1.07 ± 0.15, respectively. There was a statistically significant difference between the two groups (p = 0.001). There was a statistically significant and moderate linear correlation between serum uric acid level and mean CIMT (r = 0.402; p = 0.002). Univariate and multivariate linear regression analyses were performed to identify variables that could independently affect the mean CIMT value. According to analysis, uric acid (p < 0.001), hypertension (p = 0.008), albumin (p = 0.029), and C-reactive protein (p = 0.042) were found independent risk factors for mean CIMT value.

DISCUSSION

We found a significant relationship between serum uric acid level and CIMT, which indicates carotid atherosclerosis. Serum uric acid level is a low-cost laboratory parameter that can be measured in almost all laboratories, and it may be valuable in the hemodialysis patient group to identify patients at high risk of carotid atherosclerosis.

Causal factors of cardiovascular disease in end-stage renal disease with maintenance hemodialysis: a longitudinal and Mendelian randomization study

Background

The risk factors of cardiovascular disease (CVD) in end-stage renal disease (ESRD) with hemodialysis remain not fully understood. In this study, we developed and validated a clinical-longitudinal model for predicting CVD in patients with hemodialysis, and employed Mendelian randomization to evaluate the causal 6study included 468 hemodialysis patients, and biochemical parameters were evaluated every three months. A generalized linear mixed (GLM) predictive model was applied to longitudinal clinical data. Calibration curves and area under the receiver operating characteristic curves (AUCs) were used to evaluate the performance of the model. Kaplan-Meier curves were applied to verify the effect of selected risk factors on the probability of CVD. Genome-wide association study (GWAS) data for CVD (n = 218,792,101,866 cases), end-stage renal disease (ESRD, n = 16,405, 326 cases), diabetes (n = 202,046, 9,889 cases), creatinine (n = 7,810), and uric acid (UA, n = 109,029) were obtained from the large-open GWAS project. The inverse-variance weighted MR was used as the main analysis to estimate the causal associations, and several sensitivity analyses were performed to assess pleiotropy and exclude variants with potential pleiotropic effects.

Results

The AUCs of the GLM model was 0.93 (with accuracy rates of 93.9% and 93.1% for the training set and validation set, sensitivity of 0.95 and 0.94, specificity of 0.87 and 0.86). The final clinical-longitudinal model consisted of 5 risk factors, including age, diabetes, ipth, creatinine, and UA. Furthermore, the predicted CVD response also allowed for significant (p < 0.05) discrimination between the Kaplan-Meier curves of each age, diabetes, ipth, and creatinine subclassification. MR analysis indicated that diabetes had a causal role in risk of CVD (β = 0.088, p < 0.0001) and ESRD (β = 0.26, p = 0.007). In turn, ESRD was found to have a causal role in risk of diabetes (β = 0.027, p = 0.013). Additionally, creatinine exhibited a causal role in the risk of ESRD (β = 4.42, p = 0.01).

Conclusions

The results showed that old age, diabetes, and low level of ipth, creatinine, and UA were important risk factors for CVD in hemodialysis patients, and diabetes played an important bridging role in the link between ESRD and CVD.

Uric acid en route to gout

Gout and hyperuricemia (HU) have generated immense attention due to increased prevalence. Gout is a multifactorial metabolic and inflammatory disease that occurs when increased uric acid (UA) induce HU resulting in monosodium urate (MSU) crystal deposition in joints. However, gout pathogenesis does not always involve these events and HU does not always cause a gout flare. Treatment with UA-lowering therapeutics may not prevent or reduce the incidence of gout flare or gout-associated comorbidities. UA exhibits both pro- and anti-inflammation functions in gout pathogenesis. HU and gout share mechanistic and metabolic connections at a systematic level, as shown by studies on associated comorbidities. Recent studies on the interplay between UA, HU, MSU and gout as well as the development of HU and gout in association with metabolic syndromes, non-alcoholic fatty liver disease (NAFLD), and cardiovascular, renal and cerebrovascular diseases are discussed. This review examines current and potential therapeutic regimens and illuminates the journey from disrupted UA to gout.

Longitudinal uric acid has nonlinear association with kidney failure and mortality in chronic kidney disease

We investigated the shape of the relationship between longitudinal uric acid (UA) and the hazard of kidney failure and death in chronic kidney disease (CKD) patients, and attempted to identify thresholds associated with increased hazards. We included CKD stage 3-5 patients from the CKD-REIN cohort with one serum UA measurement at cohort entry. We used cause-specific multivariate Cox models including a spline function of current values of UA (cUA), estimated from a separate linear mixed model. We followed 2781 patients (66% men, median age, 69 years) for a median of 3.2 years with a median of five longitudinal UA measures per patient. The hazard of kidney failure increased with increasing cUA, with a plateau between 6 and 10 mg/dl and a sharp increase above 11 mg/dl. The hazard of death had a U-shape relationship with cUA, with a hazard twice higher for 3 or 11 mg/dl, compared to 5 mg/dl. In CKD patients, our results indicate that UA above 10 mg/dl is a strong risk marker for kidney failure and death and that low UA levels below 5 mg/dl are associated with death before kidney failure.

Urate-lowering therapy for patients with gout on hemodialysis

OBJECTIVE

Gout is the most common form of inflammatory arthritis and is caused by deposition of monosodium urate crystals resulting from a high burden of uric acid (UA). High UA burden also has been associated with increased morbidity and mortality in the general population and progression to chronic kidney disease. In persons with gout and end-stage renal disease (ESRD), prior studies suggest that UA levels decrease after initiation of hemodialysis (HD). We evaluated UA level and the use of urate-lowering therapies (ULTs) in patients with gout and ESRD on HD.

METHODS

We performed a retrospective review of patients with gout and ESRD seen at a large urban public hospital (The MetroHealth System). We extracted data from the medical record (Epic) for patients diagnosed with gout and ESRD on HD. The main outcomes were the UA level and the use of ULTs before and after HD initiation.

RESULTS

We identified 131 patients with gout on HD. Of these, 21 patients had crystal proven gout diagnosis, 10 of whom had data on UA level pre-HD and post-HD and were included in the analysis. For the total sample (N = 21), the mean age was 65 years, 7 were female and 20 were African American. Mean pre-HD and post-HD UA levels were 8.4 and 3.98 mg/dL respectively. Twenty-one patients were receiving ULT pre-HD, 11 discontinued post-HD.

CONCLUSION

Among patients with gout and ESRD, we observed a decrease in UA level associated with initiation of HD. For this group, discontinuation of ULTs may be appropriate.

High serum uric acid trajectories are associated with risk of myocardial infarction and all-cause mortality in general Chinese population

Background

Long-term patterns of serum uric acid (SUA) and their association with the risk of myocardial infarction (MI) and mortality are poorly characterized as prior studies measured SUA at a single time point. This study aimed to identify SUA trajectories and determine their associations with incident MI and all-cause mortality.

Methods

We included 85,503 participants who were free of MI in or prior 2012 from the Kailuan study. SUA trajectories during 2006–2012 were identified by group-based trajectory modeling. Cox proportional hazard models were used to assess the association of SUA trajectories with MI and all-cause mortality.

Results

We identified three SUA trajectories during 2006–2012: low-stable (n=44,124, mean SUA: 236–249 μmol/L), moderate-stable (n=34,431, mean SUA: 324–354 μmol/L) and high-stable (n=6,984, mean SUA: 425–463 μmol/L). During a median follow-up of 6.8 years, we documented 817 (0.96%) incident MI and 6498 (7.60%) mortality. Compared with the low-stable group, high-stable group experienced a higher risk of MI (hazard ratio [HR], 1.35; 95% confidence [CI], 1.07–1.71) and all-cause mortality (HR, 1.22; 95% CI, 1.12–1.33). Multiple sensitivity analyses yielded similar results. Additionally, the association of SUA trajectory with MI and all-cause mortality was more pronounced in individuals without a history of hypertension (P-interaction=0.0359) and those aged <60 years (P-interaction<0.0001), respectively.

Conclusions

Higher SUA trajectories were associated with altered risk of MI and all-cause mortality, suggesting that monitoring SUA trajectory may assist in identifying subpopulations at higher risk of MI and all-cause mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02812-y.

Serum Galectin-3 levels and all-cause and cardiovascular mortality in maintenance hemodialysis patients: a prospective cohort study

Background

Higher serum galectin-3 levels are related to adverse outcomes in different disease states. However, the association of galectin-3 with mortality in the maintenance hemodialysis (HD) population has not been fully described. Thus, we aimed to assess the predictive significance of galectin-3 for all-cause and cardiovascular (CV) mortality through a Chinese maintenance HD population.

Methods

A prospective cohort study was conducted in five hundred and six patients with end-stage renal disease who underwent hemodialysis at Dalian Central Hospital before December 31, 2014. Serum galectin-3 levels were measured at baseline and classified as high (> 8.65 ng/ml) or low (≤ 8.65 ng/ml) according to the “X-tile” program. Primary and secondary outcomes were all-cause and CV mortality, respectively. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated by the Cox proportional hazards regression models.

Results

During the median follow-up of 60 months, there were 188 all-cause deaths and 125 CV deaths. Compared with maintenance HD population with galectin-3 ≤ 8.65 ng/ml, the adjusted HR for all-cause mortality among those with galectin-3 >  8.65 ng/ml was 1.59 (CI: 0.96–2.65, p = 0.07). Furthermore, multivariable analysis showed that maintenance HD patients with galectin-3 >  8.65 ng/ml had a 2.13-fold higher risk of CV death than those with galectin-3 ≤ 8.65 ng/ml (HR = 2.13, 95% CI 1.07–4.26).

Conclusion

Galectin-3 is an independent predictor of CV mortality in maintenance HD patients.

The effect of hyperkalemia and long inter-dialytic interval on morbidity and mortality in patients receiving hemodialysis: a systematic review

BACKGROUND

Patients with chronic kidney disease, especially those receiving hemodialysis (HD), are at risk of hyperkalemia (HK). This systematic review aimed to evaluate the prevalence of HK in patients with renal disease receiving HD and collate evidence on the effect of HK and differing HD patterns (i.e., long vs. short inter-dialytic intervals [LIDI and SIDI, respectively] in a thrice weekly schedule) on mortality.

METHODS

Comprehensive searches were conducted across six databases and selected conference proceedings by two independent reviewers up to September 2020. A hundred and two studies reporting frequency of HK, mortality, or cardiovascular (CV) outcomes in adult patients with acute, chronic or end-stage renal disease in receipt of HD were included. Narrative synthesis of results was undertaken with key findings presented in tables and figures.

RESULTS

Median prevalence of HK in patients with renal disease receiving HD was 21.6% and increased in patients receiving concomitant medications - mainly renin-angiotensin-aldosterone system inhibitors and potassium-sparing diuretics. Associations between elevated potassium levels and increased risk of both all-cause and CV mortality in the HD population were consistent across the included studies. In addition, there was a rise in all-cause and CV mortality on the day following LIDI compared with the day after the two SIDIs in patients on HD.

CONCLUSIONS

Evidence identified in this systematic review indicates a relationship between HK and LIDI with mortality in patients with renal disease receiving HD, emphasizing the need for effective monitoring and management to control potassium levels both in emergency and chronic HD settings.

Relationship between serum uric acid, all-cause mortality and cardiovascular mortality in peritoneal dialysis patients: systematic review and meta-analysis of cohort studies

OBJECTIVES

To analyse the relationship between serum uric acid (SUA), all-cause and cardiovascular (CV) mortality in peritoneal dialysis (PD) patients to inform clinical practice and future research.

DESIGN

A systematic review of observational studies.

DATA SOURCES

PubMed, Embase, Web of Science, the Cochrane Library, China National Knowledge Infrastructure (CNKI), SinoMed, Chinese Science and Technology Journal Database (VIP) and Wan Fang databases were searched from their inception to January 2021 for cohort and case-control studies reporting SUA and mortality in patients with PD.

METHODS

The Newcastle-Ottawa Quality Assessment Scale was used to appraise quality of cohort and case-control studies. Effect estimates were presented as HRs with 95% CIs in a meta-analysis using STATA V.16.0. Data not suitable for pooling were synthesised qualitatively.

RESULTS

Fourteen cohort studies with 24 022 patients were included. No case-control studies were identified. For prospective cohort studies, pooled results for the highest SUA category were significantly greater than the lowest for all-cause (one study; 1278participants; HR 1.79; 95% CI 1.17 to 2.75) and CV mortality (one study; 1278 participants; HR 2.63; 1.62-4.27). An increase of 1 mg/dL in SUA level was associated with a 16% increased risk of all-cause mortality (one study; 1278 participants; HR 1.16; 1.03-1.32) and 34% increased CV mortality risk (one study; 1278 participants; HR 1.34; 1.16-1.55). For retrospective cohort studies, the highest SUA category did not demonstrate an elevated all-cause (five studies; 4570 participants; HR 1.09; 0.70-1.70) or CV mortality (three studies; 3748 participants; HR 1.00; 0.44-2.31) compared with the lowest SUA category. Additionally, there was no increase in all-cause (eight studies; 11 541 participants; HR 0.94; 0.88-1.02) or CV mortality (three studies; 7427 participants; HR 0.90; 0.76-1.06) for every 1 mg/dL increase in SUA level.

CONCLUSIONS

Results of prospective and retrospective cohort studies were inconsistent. Consequently, prospective, multicentre, long-term follow-up studies are required to confirm the relationship between SUA and mortality in patients with PD.

Serum Uric Acid and Mortality in Patients with Chronic Kidney Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Existing studies suggested conflicting relationships between serum uric acid (SUA) and mortality in CKD patients. The present meta-analysis aimed to determine whether SUA can be a predictor for mortality in CKD cohorts.

METHOD

A systematical search was conducted on PubMed, EMBASE, and The Cochrane Library to identify studies reporting the relationship between SUA level and all-cause and cardiovascular mortality in CKD populations. In addition, random-effects models were adopted to calculate the hazard ratios (HRs) and corresponding 95% confidence intervals (CIs).

RESULTS

On the whole, 29 studies were involved. In the present meta-analysis, patients exhibiting the maximum SUA level showed an association with a significantly higher risk for all-cause mortality (HR, 1.30; 95% CI, 1.06-1.59) compared with patients exhibiting the minimum SUA level. As revealed from the meta-analysis of 8 studies, low level of SUA was another predictor for all-cause mortality in patients with CKD (HR, 1.36; 95% CI, 1.20-1.54). No significant relationship was identified between SUA and cardiovascular mortality.

CONCLUSIONS

Higher and lower SUA levels are both associated with significantly increased risk of all-cause mortality in patients with CKD. A appreciate dose of treatment of lowering SUA agents should be confirmed.

Visit-to-visit variability of serum uric acid measurements and the risk of all-cause mortality in the general population

Background

Evidence on longitudinal variability of serum uric acid (SUA) and risk of all-cause mortality in the general population is limited, as many prior studies focused on a single measurement of SUA.

Methods

A total of 53,956 participants in the Kailuan study who underwent three health examinations during 2006 to 2010 were enrolled. Variability of SUA was measured using the coefficient of variation (primary index), standard deviation, average real variability, and variability independent of the mean. Cox proportional hazard regressions were used to calculate the hazard ratio (HR) and 95% confidence interval (CI) for the association of variability of SUA with subsequent risk of all-cause mortality, considering its magnitude and the direction and across different baseline SUA categories.

Results

Over a median follow-up of 7.04 years, 2728 participants died. The highest variability of SUA was associated with an increased risk of all-cause mortality, the HR was 1.33 (95% CI, 1.20–1.49) compared with the lowest variability. In this group, both a large fall (HR, 1.28; 95% CI, 1.14–1.44) and rise (HR, 1.18; 95% 1.05–1.32) in SUA were related to risk of all-cause mortality. These associations were similar across different baseline SUA categories. Consistent results were observed in alternative measures of SUA variability. Moreover, individuals with higher variability in SUA were more related to common risk factors than those with stable SUA.

Conclusions

Higher variability in SUA was independently associated with the risk of all-cause mortality irrespective of baseline SUA and direction of variability in the general population.

Why Does Hyperuricemia Not Necessarily Induce Gout?

Hyperuricemia is a risk factor for gout. It has been well observed that a large proportion of individuals with hyperuricemia have never had a gout flare(s), while some patients with gout can have a normuricemia. This raises a puzzle of the real role of serum uric acid (SUA) in the occurrence of gout flares. As the molecule of uric acid has its dual effects in vivo with antioxidant properties as well as being an inflammatory promoter, it has been placed in a delicate position in balancing metabolisms. Gout seems to be a multifactorial metabolic disease and its pathogenesis should not rely solely on hyperuricemia or monosodium urate (MSU) crystals. This critical review aims to unfold the mechanisms of the SUA role participating in gout development. It also discusses some key elements which are prerequisites for the formation of gout in association with the current therapeutic regime. The compilation should be helpful in precisely fighting for a cure of gout clinically and pharmaceutically.

Elevated serum uric acid and risk of cardiovascular or all-cause mortality in maintenance hemodialysis patients: A meta-analysis

BACKGROUND AND AIMS

Studies have shown inconsistent results about the association between serum uric acid (SUA) levels and mortality in hemodialysis patients. We performed this meta-analysis to determine whether higher SUA values comprised a risk factor of cardiovascular or all-cause mortality in maintenance hemodialysis patients.

METHODS AND RESULTS

Pubmed, Embase and the Cochrane library were searched up to August 31, 2020 for the longitudinal studies that investigated the association between the elevated SUA and cardiovascular or all-cause mortality risk in maintenance hemodialysis patients. Pooled adjusted hazard ratios (HR) and corresponding 95% confidence interval (CI) were calculated using a random-effects model. We included 10 studies with an overall sample of 264,571 patients with hemodialysis in this meta-analysis. Patients with the highest SUA were associated with a decreased risk of cardiovascular mortality (HR = 0.72, 95% CI 0.59-0.87) compared with patients with the lowest SUA after adjustment for potential confounders in a random effects model. Moreover, for each increase of 1 mg/dl of SUA, the overall risks of all-cause and cardiovascular mortality decreased by 6% and 9%, respectively (HR = 0.94, 95% CI 0.90-0.99; HR = 0.91, 95% CI 0.89-0.94).

CONCLUSION

Elevated SUA levels are strongly and independently associated with lower risk of cardiovascular mortality in maintenance hemodialysis patients. More designed studies, especially randomized controlled trials, should be conducted to determine whether high SUA levels is an independent risk factor of all-cause mortality in hemodialysis patients.

U-Shaped Relationship Between Cardiovascular Mortality and Serum Uric Acid May Be Attributed to Stroke- and Heart-Specific Mortality, Respectively, Among Hypertensive Patients: A Nationally Representative Cohort Study

BACKGROUND Serum uric acid (UA) is involved in the development of hypertension. However, its impact on mortality in hypertension remains unclear. We aimed to assess the association of cardiovascular and all-cause mortality with UA in a hypertensive population. MATERIAL AND METHODS This study included 15 583 hypertensive patients from the NHANES study during 1999-2014. Weighted Cox regression analyses and cubic spline fitting were used to assess the relationship between UA and mortality risk. RESULTS Over a median follow-up of 7.4 years (116 351 person-years), a total of 3291 deaths occurred. Mortality was examined according to 5 predefined UA levels: £3.5, 3.5-5, 5-6, 6-7.5, and >7.5 mg/dL. In multivariable analysis with 5-6 mg/dL as a reference, the hazard ratios (95% confidence interval) of total mortality across the 5 groups were 1.40 (1.05-1.88), 1.08 (0.95-1.21), 1.00 (reference), 1.14 (1.02-1.29), and 1.74 (1.50-2.02), respectively. According to a restricted cubic spline, we noted a U-shaped relationship between UA and total mortality. The U-shaped relationship between UA and cardiovascular mortality remained in both females and males. The increased cardiovascular mortality in the lowest and highest UA groups was attributed to stroke and heart-specific mortality, respectively. However, serum UA was not significantly associated with cancer mortality. CONCLUSIONS Our findings showed a U-shaped relationship between serum UA levels and total and cardiovascular mortality in patients with hypertension. Furthermore, low UA was associated with stroke mortality, while higher UA was associated with heart-related mortality. Further research is needed to identify the potential mechanisms of UA in hypertension.