Anemia and the onset of gout in a population-based cohort of adults: Atherosclerosis Risk in Communities study

Association between serum iron status and the risk of five bone and joint-related diseases: a Mendelian randomization analysis

Background

According to reports, iron status has been associated with the risk of bone and joint-related diseases. However, the exact role of iron status in the development of these conditions remains uncertain.

Method

We obtained genetic data on iron status, specifically serum iron, ferritin, transferrin saturation (TSAT), and transferrin, as well as data on five common bone and joint-related diseases (osteoarthritis, osteoporosis, rheumatoid arthritis [RA], ankylosing spondylitis [AS], and gout) from independent genome-wide association studies involving individuals of European ancestry. Our primary approach for causal estimation utilized the inverse variance weighted (IVW) method. To ensure the reliability of our findings, we applied complementary sensitivity analysis and conducted reverse causal analysis.

Result

Using the IVW method, we revealed a positive causal relationship between ferritin levels and the risk of osteoarthritis (OR [95% CI], 1.0114 [1.0021-1.0207]). Besides, we identified a protective causal relationship between serum iron levels and TSAT levels in the risk of RA (OR [95% CI] values of serum iron and TSAT were 0.9987 [0.9973-0.9999] and 0.9977 [0.9966-0.9987], respectively). Furthermore, we found a positive causal relationship between serum iron levels and the risk of AS (OR [95% CI], 1.0015 [1.0005-1.0026]). Regarding gout, both serum iron and TSAT showed a positive causal relationship (OR [95% CI] values of 1.3357 [1.0915-1.6345] and 1.2316 [1.0666-1.4221] for serum iron and TSAT, respectively), while transferrin exhibited a protective causal relationship (OR [95% CI], 0.8563 [0.7802-0.9399]). Additionally, our reverse causal analysis revealed a negative correlation between RA and ferritin and TSAT levels (OR [95% CI] values of serum iron and TSAT were 0.0407 [0.0034-0.4814] and 0.0049 [0.0002-0.1454], respectively), along with a positive correlation with transferrin (OR [95% CI], 853.7592 [20.7108-35194.4325]). To ensure the validity of our findings, we replicated the results through sensitivity analysis during the validation process.

Conclusion

Our study demonstrated a significant correlation between iron status and bone and joint-related diseases.

Association between Impella device support and elevated rates of gout flares: a retrospective propensity-matched study

BACKGROUND

Impella is an advanced ventricular assist device frequently used as a bridge to heart transplantation. The association of Impella with increased rates of gout flares has not been studied. Our primary aim is to determine the rates of gout flares in patients on Impella support.

METHODOLOGY

A retrospective study was conducted between January 2017 and September 2022 involving all patients who underwent heart transplantation. The cohort was divided into two groups based on Impella support for statistical analysis. In patients receiving Impella support, outcome measures were compared based on the development of gout flares. 1:1 nearest neighbor propensity match, as well as inverse propensity of treatment weighted analyses, were performed to explore the causal relationship between impella use and gout flare in our study population.

RESULTS

Our analysis included 213 patients, among which 42 (19.71%) patients were supported by Impella. Impella and non-Impella groups had similar age, race, and BMI, but more males were in the Impella group. Gout and chronic kidney disease were more prevalent in Impella-supported patients, while coronary artery disease was less common. The prevalence of gout flare was significantly higher in Impella patients (30.9% vs. 5.3%). 42 Impella-supported patients were matched with 42 patients from the non-impella group upon performing a 1:1 propensity matching. Impella-supported patients were noted to have a significantly higher risk of gout flare (30.9% vs. 7.1%, SMD = 0.636), despite no significant difference in pre-existing gout history and use of anti-gout medications. Impella use was associated with a significantly increased risk of gout flare in unadjusted (OR 8.07), propensity-matched (OR 5.83), and the inverse propensity of treatment-weighted analysis (OR 4.21).

CONCLUSION

Our study is the first to identify the potential association between Impella support and increased rates of gout flares in hospitalized patients. Future studies are required to confirm this association and further elucidate the biological pathways. It is imperative to consider introducing appropriate measures to prevent and promptly manage gout flares in Impella-supported patients.

Identification of hub genes and transcription factors in patients with primary gout complicated with atherosclerosis

Evidence shows that primary gout is prone to develop to atherosclerosis, but the mechanism of its occurrence is still not fully clarified. The aim of this study was to explore the molecular mechanism of the occurrence of this complication in gout. The gene expression profiles of primary gout and atherosclerosis were downloaded from the gene expression omnibus database. Overlapping differentially expressed genes (DEGs) between gout and atherosclerosis were identified. The biological roles of common DEGs were explored through enrichment analyses. Hub genes were identified using protein-protein interaction networks. The immune infiltrations of 28 types of immune cells in gout and control samples from GSE160170 were evaluated by the ssGSEA method. Transcription factors (TFs) were predicted using Transcriptional Regulatory Relationships Unraveled by Sentence Based Text Mining (TRRUST) database. A total of 168 overlapping DEGs were identified. Functional enrichment analyses indicated that DEGs were mostly enriched in chemokine signaling pathway, regulation of actin cytoskeleton, and TNF signaling pathway. CytoScape demonstrated 11 hub genes and two gene cluster modules. The immune infiltration analysis showed that the expression of DEGs in gout was significantly upregulated in activated CD4 T cells, gamma delta T cells, T follicular helper cell, CD56dim natural killer cells, and eosinophil. TRRUST predicted one TF, RUNX family transcription factor 1. Our study explored the pathogenesis of gout with atherosclerosis and discovered the immune infiltration of gout. These results may guide future experimental research and clinical transformation.

Association of serum uric acid with anemia in U.S. adults: a cross-sectional study using secondary data

BACKGROUND

High serum uric acid (SUA) is a risk factor of cardiovascular disease (CVD). Abnormal SUA have been correlated with a significant increase in mortality. Anemia is an independent predictor of mortality and CVD. To date, no study has investigated the relationship between SUA and anemia. Here, we explored the correlation between SUA and anemia in the American population.

METHODS

The cross-sectional study involved 9205 US adults from NHANES (2011-2014). The relationship between SUA and anemia was explored using multivariate linear regression models. Two-piecewise linear regression model, generalized additive models (GAM) and smooth curve fitting were performed to explore the non-linear relationships between SUA and anemia.

RESULTS

We found a U-shaped non-linear relationship between SUA and anemia. The inflection point of the SUA concentration curve was 6.2 mg/dL. The ORs (95% CIs) for anemia on the left and right of the inflection point were 0.86 (0.78-0.95) and 1.33 (1.16-1.52), respectively. The 95% CI of inflection point was 5.9-6.5 mg/dL. The findings showed that both genders presented a U-shaped correlation. Safe ranges of SUA in men and women were 6-6.5 and 4.3-4.6 mg/dL, respectively.

CONCLUSIONS

Both high and low SUA levels were correlated with increased risk of anemia, and a U-shaped relationship was observed between SUA and anemia.

The relationship between hyperuricemia and anemia and metabolic syndrome in Korean adults: The Korea National Health and Nutrition Examination Survey 2019

AIM

The present study was conducted to assess the relationship between hyperuricemia and anemia in Korean adults with or without metabolic syndrome (MetS).

METHODS

Data from 6073 adults (age ≥ 20 years) in the Eighth Korean National Health and Nutrition Examination Survey (2019) were analyzed.

RESULTS

Several key findings were identified. First, after adjusting for the related variables, the hemoglobin [Hb] level in the hyperuricemia subgroup (uric acid [UA] ≥ 7.0 mg/dL in men or ≥ 6.0 mg/dL in women) was higher than in the normouricemia subgroup (UA < 7.0 mg/dL in men or < 6.0 mg/dL in women) in subjects with non-MetS (p = 0.005), whereas it was lower than in the normouricemia subgroup in subjects with MetS (p = 0.032). Second, after adjusting for the related variables, the odds ratio (OR) of anemia (Hb < 13.0 g/dL in men or < 12 g/dL in women), using the normouricemia subgroup as a reference, was negatively significant for the hyperuricemia subgroup in subjects with non-MetS (OR, 0.478; 95 % CI, 0.300-0.761) but positively significant for the hyperuricemia subgroup in subjects with MetS (OR, 1.765; 95 % CI, 1.160-2.198).

CONCLUSIONS

Hyperuricemia was associated with a decrease in anemia in non-MetS but an increase in anemia in MetS.

Gout among Patients with Dialysis: Prevalence, Associated Factors, Treatment Patterns, and Outcomes-Population-Based Retrospective Cohort Study

Key Points

Population-based retrospective cohort study to evaluate clinical correlates of gout and its impact on patients undergoing chronic dialysis. 13.5% of US dialysis-dependent patients had gout and were older and male, with a higher prevalence of hypertension and cardiovascular disease. Gout diagnosis was associated with a higher incidence of cardiovascular conditions, levels of anemia, hospitalization, and mortality.

Background

An association between gout and nondialysis chronic renal disease has long been recognized, yet limited research exists regarding prevalence, treatment, anemia management, and outcomes in patients with ESKD undergoing dialysis.

Methods

Using data from United States Renal Data System, we conducted a population-based retrospective cohort study in adult patients covered by Medicare and on dialysis in 2017. Multivariate logistic regression models were used to estimate potential factors and odds of gout diagnosis. Antigout medications and impact on anemia management were assessed and compared between gout and nongout dialysis patients using descriptive and regression analyses. Associations for all-cause mortality and cardiovascular-related hospitalizations during 1 year of study follow-up were compared between gout and nongout patients using multivariate Cox regression models.

Results

Of 231,841 ESKD Medicare patients in 2017 undergoing continuous dialysis, 31,300 (13.5%) had one or more gout diagnostic code(s). Increased odds of having a gout diagnosis were independently associated with older age, male sex, Asian race, obesity, hypertension, and cardiovascular disease. Gout diagnosis was associated with higher prevalence for anemia as indicated by increased erythropoietin-stimulating agent requirements (odds ratio=1.18 for high versus low erythropoietin-stimulating agent dose, 95% confidence interval [95% CI], 1.14 to 1.22) and likelihood of blood transfusions (odds ratio=1.34, 95% CI, 1.30 to 1.38). During the 1-year study follow-up, mortality among gout versus nongout patients was higher by 3% (95% CI, 0 to 6) and a composite association of mortality and cardiovascular disease hospitalization was higher by 6% (95% CI, 3 to 9) after adjusting for comorbid conditions.

Conclusions

A gout diagnosis was found in 13.5% of US dialysis-dependent patients and was associated with a higher burden of comorbid cardiovascular conditions as well as an elevated incidence of hospitalization and mortality. These observations improve our current understanding of gout among the dialysis population and highlight the importance of new and better treatments to improve outcomes.

Common and rare variant associations with clonal haematopoiesis phenotypes

Clonal haematopoiesis involves the expansion of certain blood cell lineages and has been associated with ageing and adverse health outcomes^1-5. Here we use exome sequence data on 628,388 individuals to identify 40,208 carriers of clonal haematopoiesis of indeterminate potential (CHIP). Using genome-wide and exome-wide association analyses, we identify 24 loci (21 of which are novel) where germline genetic variation influences predisposition to CHIP, including missense variants in the lymphocytic antigen coding gene LY75, which are associated with reduced incidence of CHIP. We also identify novel rare variant associations with clonal haematopoiesis and telomere length. Analysis of 5,041 health traits from the UK Biobank (UKB) found relationships between CHIP and severe COVID-19 outcomes, cardiovascular disease, haematologic traits, malignancy, smoking, obesity, infection and all-cause mortality. Longitudinal and Mendelian randomization analyses revealed that CHIP is associated with solid cancers, including non-melanoma skin cancer and lung cancer, and that CHIP linked to DNMT3A is associated with the subsequent development of myeloid but not lymphoid leukaemias. Additionally, contrary to previous findings from the initial 50,000 UKB exomes⁶, our results in the full sample do not support a role for IL-6 inhibition in reducing the risk of cardiovascular disease among CHIP carriers. Our findings demonstrate that CHIP represents a complex set of heterogeneous phenotypes with shared and unique germline genetic causes and varied clinical implications.

Risk Factors for Postsurgical Gout Flares after Thoracolumbar Spine Surgeries

Gouty arthritis is the most common form of inflammatory arthritis and flares frequently after surgeries. Such flares impede early patient mobilization and lengthen hospital stays; however, little has been reported on gout flares after spinal procedures. This study reviewed a database of 6439 adult patients who underwent thoracolumbar spine surgery between January 2009 and June 2021, and 128 patients who had a history of gouty arthritis were included. Baseline characteristics and operative details were compared between the flare-up and no-flare groups. Multivariate logistic regression was used to analyze predictors and construct a predictive model of postoperative flares. This model was validated using a receiver operating characteristic (ROC) curve analysis. Fifty-six patients (43.8%) had postsurgical gout flares. Multivariate analysis identified gout medication use (odds ratio [OR], 0.32; 95% confidence interval [CI], 0.14−0.75; p = 0.009), smoking (OR, 3.23; 95% CI, 1.34−7.80; p = 0.009), preoperative hemoglobin level (OR, 0.68; 95% CI, 0.53−0.87; p = 0.002), and hemoglobin drop (OR, 1.93; 95% CI, 1.25−2.96; p = 0.003) as predictors for postsurgical flare. The area under the ROC curve was 0.801 (95% CI, 0.717−0.877; p < 0.001). The optimal cut-off point of probability greater than 0.453 predicted gout flare with a sensitivity of 76.8% and specificity of 73.2%. The prediction model may help identify patients at an increased risk of gout flare.

Thirty-Day Hospital Readmissions for Acute Gout in the United States: Analysis of the Nationwide Readmission Database

BACKGROUND/OBJECTIVE

The aims of this study were to describe the rates and characteristics of nonelective 30-day readmission among adult patients hospitalized for acute gout and to assess predictors of readmission.

METHODS

We analyzed the 2017 Nationwide Readmission Database. Gout hospitalizations were identified using the International Classification of Diseases, Tenth Revision, Clinical Modification code. Hospitalizations for adult patients were included. We excluded planned or elective readmissions. We utilized χ2 tests to compare baseline characteristics between readmissions and index hospitalizations. We used multivariate Cox regression to identify independent predictors of readmissions.

RESULTS

A total of 11,727 index adult hospitalizations with acute gout listed as the principal diagnosis were discharged alive and included. One thousand five hundred ninety-four (13.6%) readmissions occurred within 30 days. Acute gout was the most common reason for readmission. Readmissions had higher inpatient mortality (2.4% vs 0.1%, p < 0.0001), greater mean age (68.1 vs 67.0 years, p = 0.021), and longer hospital length of stay (5.9 vs 3.8 days, p < 0.0001) compared with index hospitalizations. Charlson Comorbidity Index scores of ≥2 (score 2: adjusted hazards ratio [AHR], 1.67; p = 0.001; score ≥3: AHR, 2.08; p < 0.0001), APR-DRG (All Patients Refined Diagnosis Related Groups) severity levels ≥2 (level 2: AHR, 1.43; p = 0.044; level 3: AHR, 1.83; p = 0.002; level 4: AHR, 2.38; p = 0.002), admission to metropolitan hospital (AHR, 1.83; p = 0.012), atrial fibrillation (AHR, 1.31; p = 0.004), and anemia (AHR, 1.30; p = 0.001) were significantly associated with 30-day readmissions.

CONCLUSIONS

Acute gout readmissions were associated with worse outcomes compared with index hospitalizations. Charlson Comorbidity Index scores ≥2, APR-DRG severity levels ≥2, admission to metropolitan hospital, atrial fibrillation, and anemia were significant predictors of readmission.

A retrospective cross-sectional study of the associated factors of hyperuricemia in patients with chronic kidney disease

Objective

To investigate the prevalence of hyperuricemia in patients at different stages of chronic kidney disease (CKD) and the association of serum uric acid (SUA) with several clinical factors in a retrospective cross-sectional study of non-dialysis CKD patients at two hospitals in Shanghai, China.

Methods

The prevalence of hyperuricemia in CKD patients and the association of SUA with other clinical factors were examined using analysis of variance, chi-squared test, multivariate analysis, and other statistical methods.

Results

A total of 663 CKD patients were enrolled, of which approximately 52% had hyperuricemia. CKD patients with hyperuricemia had lower hemoglobin and estimated glomerular filtration rate (eGFR) levels but higher blood urea nitrogen, serum creatinine, and serum phosphate levels than those without hyperuricemia. Serum uric acid level was positively associated with age, blood urea nitrogen , serum creatinine, cystatin C, and serum phosphate and negatively associated with hemoglobin and eGFR. In addition, CKD patients with anemia and hyperphosphatemia had a higher prevalence of hyperuricemia than those without anemia or hyperphosphatemia.

Conclusions

The prevalence of hyperuricemia increased with CKD progression supporting the use of urate-lowering treatment for patients with CKD stage 1 to 4.

Wastewater-based estimation of the prevalence of gout in Australia

Allopurinol, a first-line gout treatment drug in Australia, was assessed as a wastewater-based epidemiology biomarker of gout via quantification of the urinary metabolite, oxypurinol in wastewater. The in-sewer stability of oxypurinol was examined using laboratory-scale sewer reactors. Wastewater from 75 wastewater treatment plants across Australia, covering approximately 52% (12.2 million) of the country's population, was collected on the 2016 census day. Oxypurinol was quantified in the wastewater samples and population-weighted mass loads calculated. Pearson and Spearman rank-order correlations were applied to investigate any link between allopurinol, other selected wastewater biomarkers, and socio-economic indicators. Oxypurinol was shown to be stable in sewer conditions and suitable as a WBE biomarker. Oxypurinol was detected in all wastewater samples. The estimated consumption of allopurinol ranged from 1.9 to 32 g/day/1000 people equating to 4.8 to 80 DDD/day/1000 people. The prevalence of gout across all tested sewer catchments was between 0.5% to 8%, with a median of 2.9% nationally. No significant positive correlation was observed between allopurinol consumption and alcohol consumption, mean age of catchment population, remoteness or higher socioeconomic status. There was a significant positive correlation with selective analgesic drug use. Wastewater analysis can be used to study gout prevalence and can provide additional insights on population level risk factors when triangulated with other biomarkers.

Dysfunctional ABCG2 gene polymorphisms are associated with serum uric acid levels and all-cause mortality in hemodialysis patients

Dysfunctional variants of ATP-binding cassette transporter subfamily G member 2 (ABCG2), a urate transporter in the kidney and intestine, are the major causes of hyperuricemia and gout. A recent study found that ABCG2 is a major transporter of uremic toxins; however, few studies have investigated the relationship between ABCG2 gene polymorphisms and mortality. This prospective cohort study of 1214 hemodialysis patients investigated the association between serum uric acid levels and ABCG2 genotype and mortality. Genotyping of dysfunctional ABCG2 variants, Q126X (rs72552713) and Q141K (rs2231142), was performed using the patients’ DNA. During the study period, 220 patients died. Lower serum uric acid levels were associated with higher mortality (hazard ratio [HR] 1.89, 95% confidence interval [CI] 1.14–3.10, P ≤ 0.001). ABCG2 dysfunction, estimated by genetic variants, had a significant positive association with serum uric acid levels (full function: 7.4 ± 1.2 mg/dl, 3/4 function: 7.9 ± 1.3 mg/dl, 1/2 function: 8.2 ± 1.4 mg/dl, ≤ 1/4 function: 8.7 ± 1.3 mg/dl, P ≤ 0.001). This association remained significant on multiple regression analysis. The Cox proportional hazard analysis indicated that the ABCG2 ≤ 1/4 function type was significantly associated with higher mortality (HR 6.66, 95% CI 2.49 to 17.8, P ≤ 0.001) than the other function types. These results showed that ABCG2 plays a physiologically important role in uric acid excretion, and that ABCG2 dysfunction is a risk factor for mortality in hemodialysis patients.

Causal associations of iron status with gout and rheumatoid arthritis, but not with inflammatory bowel disease

BACKGROUND & AIMS

We conducted a two-sample Mendelian randomization study to assess the associations of iron homeostasis with the risk of gout, rheumatoid arthritis and inflammatory bowel disease.

METHODS

Single-nucleotide polymorphisms for iron status were selected at the genome-wide significance level from a large genome-wide association study of 48 972 European-descent individuals. Summary-level data for gout, rheumatoid arthritis and inflammatory bowel disease were obtained from The Global Urate Genetics Consortium and two large genome-wide association studies, respectively. Inverse-variance weighted method with random-effects and sensitivity analyses were performed.

RESULTS

Genetic predisposition to high iron status was causally associated with higher odds of gout, lower odds of rheumatoid arthritis, but not associated with inflammatory bowel disease. The odds ratios of gout were 1.35 (95% confidence interval (CI), 1.00, 1.81; p = 0.047), 2.07 (95% CI, 1.23, 3.50; p = 0.006), 1.27 (95% CI, 1.07, 1.50; p = 0.007) and 0.69 (95% CI, 0.54, 0.90; p = 0.005) per one standard deviation increment of serum iron, ferritin, transferrin saturation, and transferrin levels, respectively. For rheumatoid arthritis, the corresponding odds ratios were 0.79 (95% CI, 0.65, 0.94; p = 0.010), 0.59 (95% CI, 0.40, 0.86; p = 0.007), 0.84 (95% CI, 0.75, 0.94; p = 0.003) and 1.28 (95% CI, 1.06, 1.55; p = 0.012).

CONCLUSIONS

Based on consistent findings for four iron biomarkers, genetically high iron status was positively associated with gout and inversely associated with rheumatoid arthritis. There was limited MR evidence supporting a causal association between iron status and inflammatory bowel disease.

Association between anemia and hyperuricemia: results from the Korean National Health and Nutrition Examination Survey

Hyperuricemia and anemia share several comorbidities, but the association between the two conditions remains unclear. The purpose of this study was to investigate the association between hyperuricemia and anemia. Data of 10794 subjects from the Korean National Health and Nutrition Examination Survey conducted in 2016-2017 were analyzed using multivariate logistic regression analyses. An association between anemia and hyperuricemia was not evident in subjects without chronic kidney disease (CKD). In patients with CKD, anemia increased the risk of hyperuricemia by 2-fold. This association remained significant when adjusting for the glomerular filtration rate. In subgroup analyses, the association of anemia with hyperuricemia was significant in subjects aged ≥65 years, and in those with diabetes or hypertension. Subgroup analyses of CKD patients showed similar results. In the current study using data from Korean representative samples, anemia in subjects with CKD was associated with a 2-fold increase in the risk of hyperuricemia, which remained significant even after adjustment for renal function.

Determinants of hyperuricemia in non-dialysed chronic kidney disease patients in three hospitals in Cameroon

BACKGROUND

Chronic kidney disease (CKD) poses a substantial health burden in sub-Saharan Africa, with risk factors ranging from communicable to non-communicable diseases. Hyperuricemia has been recently identified as a factor of progression of CKD. Identifying factors associated with hyperuricemia in CKD patients would help determine interventions to reduce CKD mortality, particularly in resources limited countries. We sought to determine the prevalence and factors associated with hyperuricemia in non-dialysed CKD adult patients in Cameroon.

METHODS

This was a cross-sectional study of non-dialysed CKD patients, conducted in 3 referral nephrology units in Cameroon. Relevant clinical and laboratory data were collected using interviewer-administered questionnaires. Serum uric acid, spot urine protein and spot urine creatinine were assessed. Associations between variables were assessed using multivariate analysis. Level of statistical significance was set at α < 0.05.

RESULTS

A sample of 103 participants was included. Mean age of study participants was 55.78 ± 12.58 years, and 59.3% were men. Sixty-nine (67%) had hyperuricemia. Patient's age (OR: 1.08, 95% CI: 1.03-1.13), estimated glomerular filtration rate (OR: 0.94, 95% CI: 0.90-0.98), spot urine protein-creatinine ratio (OR: 1.83, 95% CI: 1.07-3.12), no hypertension (OR: 0.09, 95% CI: 0.02-0.46), urate lowering therapy (OR: 4.99, 95% CI: 1.54-16.16), loop diuretics (OR: 3.39, 95% CI: 1.01-11.42), obesity (OR: 6.12, 95% CI: 1.15-32.55) and no anaemia (OR: 0.04, 95% CI: 0.00-0.29) were independently significantly associated with hyperuricemia.

CONCLUSIONS

In this sample of non-dialysed CKD patients in Cameroon, about 7 out of 10 had hyperuricemia. Hyperuricemia was independently associated with patient's age, estimated glomerular filtration rate, spot urine protein-creatinine ratio, hypertension, urate lowering therapy, loop diuretics, obesity and anaemia. More studies are required to establish causal relationships between these associations.

Co-occurrence of medical conditions: Exposing patterns through probabilistic topic modeling of snomed codes

Patients associated with multiple co-occurring health conditions often face aggravated complications and less favorable outcomes. Co-occurring conditions are especially prevalent among individuals suffering from kidney disease, an increasingly widespread condition affecting 13% of the general population in the US. This study aims to identify and characterize patterns of co-occurring medical conditions in patients employing a probabilistic framework. Specifically, we apply topic modeling in a non-traditional way to find associations across SNOMED-CT codes assigned and recorded in the EHRs of >13,000 patients diagnosed with kidney disease. Unlike most prior work on topic modeling, we apply the method to codes rather than to natural language. Moreover, we quantitatively evaluate the topics, assessing their tightness and distinctiveness, and also assess the medical validity of our results. Our experiments show that each topic is succinctly characterized by a few highly probable and unique disease codes, indicating that the topics are tight. Furthermore, inter-topic distance between each pair of topics is typically high, illustrating distinctiveness. Last, most coded conditions grouped together within a topic, are indeed reported to co-occur in the medical literature. Notably, our results uncover a few indirect associations among conditions that have hitherto not been reported as correlated in the medical literature.

Physical Function, Hyperuricemia, and Gout in Older Adults

OBJECTIVE

Gout prevalence is high in older adults and those affected are at risk of physical disability, yet it is unclear whether they have worse physical function.

METHODS

We studied gout, hyperuricemia, and physical function in 5,819 older adults (age ≥65 years) attending the 2011-2013 Atherosclerosis Risk in Communities Study visit, a prospective US population-based cohort. Differences in lower extremity function (Short Physical Performance Battery [SPPB] and 4-meter walking speed) and upper extremity function (grip strength) by gout status and by hyperuricemia prevalence were estimated in adjusted ordinal logistic regression (SPPB) and linear regression (walking speed and grip strength) models. Lower scores or times signify worse function. The prevalence of poor physical performance (first quartile) by gout and hyperuricemia was estimated using adjusted modified Poisson regression.

RESULTS

Ten percent of participants reported a history of gout and 21% had hyperuricemia. There was no difference in grip strength by history of gout (P = 0.77). Participants with gout performed worse on the SPPB test; they had 0.77 times (95% confidence interval [95% CI] 0.65, 0.90, P = 0.001) the prevalence odds of a 1-unit increase in SPPB score and were 1.18 times (95% CI 1.07, 1.32, P = 0.002) more likely to have poor SPPB performance. Participants with a history of gout had slower walking speed (mean difference -0.03; 95% CI -0.05, -0.01, P < 0.001) and were 1.19 times (95% CI 1.06, 1.34, P = 0.003) more likely to have poor walking speed. Similarly, SPPB score and walking speed, but not grip strength, were worse in participants with hyperuricemia.

CONCLUSION

Older adults with gout and hyperuricemia are more likely to have worse lower extremity, but not upper extremity, function.

Impact of gout on the risk of atrial fibrillation

OBJECTIVES

To examine the risk of atrial fibrillation (AF) at the time of first diagnosis of gout compared with matched controls and to follow incident gout patients and their matched controls after diagnosis to compare their subsequent risk of AF.

METHODS

From the UK Clinical Practice Research Data-link, 45 378 incident gout patients and 45 378 age-, sex-, practice-, registration year- and index year-matched controls were identified. Index dates were initial diagnosis date for gout patients and their matched controls. The risk of AF at diagnosis [odds ratios (ORs), using conditional logistic regression] and after the diagnosis of gout [hazard ratios (HRs), using Cox proportional models] were estimated, adjusted for BMI, smoking, alcohol consumption, ischaemic heart disease, heart failure, heart valve disease, hyperthyroidism and other comorbidities and medications.

RESULTS

The prevalence of AF at index date in gout patients (male, 72.3%; mean age, 62.4 ± 15.1 years) was 7.42% (95% CI 7.18, 7.66%) and in matched controls 2.83% (95% CI 2.67, 2.98%). The adjusted OR (95% CI) was 1.45 (1.29, 1.62). The cumulative probability of AF at 1, 2, 5 and 10 years after index date was 1.08, 2.03, 4.77 and 9.68% in gout patients and 0.43, 1.08, 2.95 and 6.33% in controls, respectively (log-rank test, P < 0.001). The adjusted HR (95% CIs) was 1.09 (1.03, 1.16).

CONCLUSION

This population-based study indicates that gout is independently associated with a higher risk of AF at diagnosis and the risk is also higher after the diagnosis.

Global epidemiology of gout: prevalence, incidence and risk factors

Gout is a crystal-deposition disease that results from chronic elevation of uric acid levels above the saturation point for monosodium urate (MSU) crystal formation. Initial presentation is mainly severely painful episodes of peripheral joint synovitis (acute self-limiting 'attacks') but joint damage and deformity, chronic usage-related pain and subcutaneous tophus deposition can eventually develop. The global burden of gout is substantial and seems to be increasing in many parts of the world over the past 50 years. However, methodological differences impair the comparison of gout epidemiology between countries. In this comprehensive Review, data from epidemiological studies from diverse regions of the world are synthesized to depict the geographic variation in gout prevalence and incidence. Key advances in the understanding of factors associated with increased risk of gout are also summarized. The collected data indicate that the distribution of gout is uneven across the globe, with prevalence being highest in Pacific countries. Developed countries tend to have a higher burden of gout than developing countries, and seem to have increasing prevalence and incidence of the disease. Some ethnic groups are particularly susceptible to gout, supporting the importance of genetic predisposition. Socioeconomic and dietary factors, as well as comorbidities and medications that can influence uric acid levels and/or facilitate MSU crystal formation, are also important in determining the risk of developing clinically evident gout.

Plasma Urate and Risk of a Hospital Stay with AKI: The Atherosclerosis Risk in Communities Study

BACKGROUND AND OBJECTIVES

Higher urate levels are associated with higher risk of CKD, but the association between urate and AKI is less established. This study evaluated the risk of hospitalized AKI associated with urate concentrations in a large population-based cohort. To explore whether urate itself causes kidney injury, the study also evaluated the relationship between a genetic urate score and AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A total of 11,011 participants from the Atherosclerosis Risk in Communities study were followed from 1996-1998 (baseline) to 2010. The association between baseline plasma urate and risk of hospitalized AKI, adjusted for known AKI risk factors, was determined using Cox regression. Interactions of urate with gout and CKD were tested. Mendelian randomization was performed using a published genetic urate score among the participants with genetic data (n=7553).

RESULTS

During 12 years of follow-up, 823 participants were hospitalized with AKI. Overall, mean participant age was 63.3 years, mean eGFR was 86.3 ml/min per 1.73 m(2), and mean plasma urate was 5.6 mg/dl. In patients with plasma urate >5.0 mg/dl, there was a 16% higher risk of hospitalized AKI for each 1-mg/dl higher urate (adjusted hazard ratio, 1.16; 95% confidence interval, 1.10 to 1.23; P<0.001). When stratified by history of gout, the association between higher urate and AKI was significant only in participants without a history of gout (P for interaction=0.02). There was no interaction of CKD and urate with AKI, nor was there an association between genetic urate score and AKI.

CONCLUSIONS

Plasma urate >5.0 mg/dl was independently associated with risk of hospitalized AKI; however, Mendelian randomization did not provide evidence for a causal role of urate in AKI. Further research is needed to determine whether lowering plasma urate might reduce AKI risk.

Comorbidities in patients with gout prior to and following diagnosis: case-control study

Objectives

To determine the burden of comorbidities in patients with gout at diagnosis and the risk of developing new comorbidities post diagnosis.

Methods

There were 39 111 patients with incident gout and 39 111 matched controls identified from the UK Clinical Practice Research Data-link. The risk of comorbidity before (ORs) and after the diagnosis of gout (HRs) were estimated, adjusted for age, sex, diagnosis year, body mass index, smoking and alcohol consumption.

Results

Gout was associated with adjusted ORs (95% CIs) of 1.39 (1.34 to 1.45), 1.89 (1.76 to 2.03) and 2.51 (2.19 to 2.86) for the Charlson index of 1–2, 3–4 and ≥5, respectively. Cardiovascular and genitourinary diseases, in addition to hyperlipidaemia, hypothyroidism, anaemia, psoriasis, chronic pulmonary diseases, osteoarthritis and depression, were associated with a higher risk for gout. Gout was also associated with an adjusted HR (95% CI) of 1.41 (1.34 to 1.48) for having a Charlson index ≥1. Median time to first comorbidity was 43 months in cases and 111 months in controls. Risks for incident comorbidity were higher in cardiovascular, genitourinary, metabolic/endocrine and musculoskeletal diseases, in addition to liver diseases, hemiplegia, depression, anaemia and psoriasis in patients with gout. After additionally adjusting for all comorbidities at diagnosis, gout was associated with a HR (95% CI) for all-cause mortality of 1.13 (1.08 to 1.18; p<0.001).

Conclusions

The majority of patients with gout have worse pre-existing health status at diagnosis and the risk of incident comorbidity continues to rise following diagnosis. The range of associated comorbidities is broader than previously recognised and merits further evaluation.