Analyses of the relationship between hyperuricemia and osteoporosis

A Mendelian randomization study of the association between serum uric acid and osteoporosis risk

Background

The relationship between serum uric acid (SUA) and osteoporosis (OP) has yielded conflicting results in observational studies. This Mendelian randomization (MR) study aims to elucidate the causal association between SUA and OP.

Methods

A two-sample MR analysis was conducted using summary-level data from genome-wide association studies (GWAS). Two sets of polygenic instruments strongly associated (p < 5 × 10-8) with SUA were extracted from the CKDGen consortium and UK biobank. Polygenic instruments associated with OP (p < 5 × 10-8) were derived from FinnGen biobank and UK biobank. Inverse variance weighting (IVW) was employed as the primary analysis method. Additionally, we utilized MR-Egger, weighted median, the simple mode method, and the weighted mode as complementary analyses. Cochran's Q statistics were used to assess heterogeneity, with MR-Egger intercept testing and MR pleiotropy residual sum and outlier (MR-PRESSO) to examine horizontal pleiotropy. Sensitivity analysis was performed using the leave-one-out method.

Results

The IVW analysis conducted across four groups confirms no significant causal relationship between SUA concentration and OP: UKB-UKB (OR: 1.001, 95% CI: 0.999-1.003, p=0.464), CKD-UKB (OR: 1.001, 95% CI: 0.999-1.003, p=0.349), UKB-Fin (OR: 0.934, 95% CI: 0.747-1.168, p=0.549), CKD-Fin (OR: 1.041, 95%CI: 0.934-1.161, p=0.470). Furthermore, additional four MR analyses corroborated these findings. Upon excluding all outliers identified by the MR-PRESSO test, no significant directional pleiotropy was observed, except for some data heterogeneity noted in the UKB-UKB group (Q=50.65, P=0.002). Additionally, a leave-one-out analysis indicated that no single SNP exerted undue influence on the results.

Conclusion

This MR analysis provides convincing genetic evidence that there is no causal association between SUA and OP, SUA is unlikely to increase or reduce the risk of OP.

Association between cardiovascular health assessed by life's essential 8 and hyperuricemia in U.S. adults: the NHANES 2009-2020

Background

This study presented the new Life's Essential 8 (LE8) framework for examining cardiovascular health (CVH) to analyze the potential relationship between the latter and hyperuricemia (HUA) in the U.S. population.

Methods

Data on individuals aged at least 20 years were collected from the National Health and Nutrition Examination Survey (NHANES) 2009-2020. Smoothed curve fitting and multivariate logistic regression analyses were then performed on a sample of 25,681 adults to explore the association between LE8 and HUA. A sensitivity analysis was conducted to examine the robustness of the research findings.

Results

The study found a strong negative association between LE8 and HUA, with an odds ratio (OR) of 0.71 and a 95% confidence interval (CI) from 0.69 to 0.73 after adjusting for multiple confounding factors. The sensitivity analysis further validated the robustness of this association. This analysis consistently showed negative associations across different genders, ages, races, and education levels (p < 0.05), but there were no significant relationships with marital status. The association between uric acid levels and LE8 displayed an inverted L-shaped curve, with an inflection point around 41.43.

Conclusions

The findings indicate a strong negative relationship between LE8 and HUA among the U.S. population, suggesting that higher scores on the LE8, which assesses CVH, were associated with reduced uric acid levels. The consistent negative association underscores the LE8 framework's potential as a valuable tool for understanding and managing HUA in CVH.

The Prevalence of Hyperuricemia and the Association Between Hyperuricemia and Age in Patients with Psychiatric Disorders to a General Hospital: A Cross-Section Study

Purpose

In clinical work, it has been found that the prevalence of hyperuricemia (HUA) is significantly higher in younger patients with psychiatric disorders, but there are few studies in this area. The present study aims to evaluate the prevalence of HUA and the relationship between the HUA and age in hospitalized patients with psychiatric disorders in the real world, and to provide a theoretical basis for clinical staff to pay attention to the metabolic indicators of younger patients and for future related studies.

Methods

This is a cross-sectional evaluation of a cohort of 1761 patients with psychiatric disorders of hospitalized. The categories of disorders designed for study included: Depression, Bipolar disorder, Schizophrenia, Anxiety, Obsessive-Compulsive disorder, Acute and transient psychotic disorder, Dissociative(conversion) disorders, Conduct disorders and Tic disorders. In addition, based on age, the participants are stratified into three groups. The authors used Kruskal-Wallis tests, chi-square tests, and multiple linear logistic regression to verify the relationship between HUA and age among hospitalized patients with psychiatric disorders.

Results

Overall, the estimated prevalence of HUA was 35.4%. The prevalence of HUA was significantly higher in individuals with 17 years and under compared to those with 45 years and above (P < 0.001). After adjusting for confounders, the prevalence of HUA remained higher at 17 years and under than at 45 years and above. Bipolar disorder can lead to an increased prevalence of HUA (P<0.05).

Conclusion

The prevalence of HUA was higher in hospitalized patients with psychiatric disorders, and the prevalence was inversely proportional to age.

Traditional Chinese medicine in osteoporosis: from pathogenesis to potential activity

Osteoporosis characterized by decreased bone density and mass, is a systemic bone disease with the destruction of microstructure and increase in fragility. Osteoporosis is attributed to multiple causes, including aging, inflammation, diabetes mellitus, and other factors induced by the adverse effects of medications. Without treatment, osteoporosis will further progress and bring great trouble to human life. Due to the various causes, the treatment of osteoporosis is mainly aimed at improving bone metabolism, inhibiting bone resorption, and promoting bone formation. Although the currently approved drugs can reduce the risk of fragility fractures in individuals, a single drug has limitations in terms of safety and effectiveness. By contrast, traditional Chinese medicine (TCM), a characteristic discipline in China, including syndrome differentiation, Chinese medicine prescription, and active ingredients, shows unique advantages in the treatment of osteoporosis and has received attention all over the world. Therefore, this review summarized the pathogenic factors, pathogenesis, therapy limitations, and advantages of TCM, aiming at providing new ideas for the prevention and treatment of OP.

Cross-sectional analysis of the correlation between serum uric acid and trabecular bone score: NHANES 2005-2008

Serum uric acid (SUA) has been discovered to be associated with bone mineral density (BMD), but its relationship with trabecular bone score (TBS) remains unclear. Thus, the aim of our study was to investigate the association between SUA levels and TBS. Our study included 5895 individuals over 20 years old (3061 men and 2834 women) from NHANES 2005-2008. To analyze the association between SUA and TBS, multivariate linear regression models with covariate adjustments were applied. Furthermore, population description, stratified analysis, single factor analysis, smooth curve fitting, interaction analysis, and threshold effect and saturation effect analysis were also conducted. After adjusting for covariates, SUA showed a strong negative relationship with total TBS (β = 0.319; 95% CI 0.145-0.494; P < 0.001). The relationship between SUA levels and total TBS was found to be nonlinear, with inflection points at 4.8 mg/dL for the overall population, 4.2 mg/dL for women, and 5.7 mg/dL for non-Hispanic whites, indicating a saturation effect. Additionally, no interactions were found in any of the subgroups. Our study found a negative association between SUA and total TBS in adults. Maintaining SUA at a saturated level can benefit in preventing osteoporosis and fractures.

Association between serum uric acid level and bone mineral density in men more than 50 years of age

Background

The results of previous studies on the association between serum uric acid levels and bone mineral density and the risk of osteoporosis are controversial. Fat free mass (FFM) is more strongly associated with bone mineral density (BMD) than it is with body fat mass (BFM). Skeletal muscle mass is assumed to contribute indirectly to the relationship between serum uric acid levels and BMD. Therefore, we aimed to evaluate the association between serum uric acid levels and BMD and abnormal BMD (at least osteopenia) by considering body composition in men aged ≥ 50 years.

Methods

This was a retrospective observational cross-sectional study. We used data obtained from 2,991 men aged ≥50 years who completed questionnaires, anthropometric surveys, laboratory tests, and bone mineral density scans. A subgroup analysis of 1,135 men who additionally underwent body composition data analysis using Inbody® was performed. Multiple linear regression analysis was used to explore the relationship between serum uric acid levels and BMD at three sites (L1-L4, Femur neck, Femur total). In addition, multiple logistic regression analysis was performed to determine the association of serum uric acid levels with abnormal BMD (at least osteopenia).

Results

Positive correlations between serum uric acid levels and BMD at the three sites (L1-L4, Femur neck, Femur total) were observed in unadjusted and fully adjusted models except the BMD of the femoral neck (P-value=0.054).Furthermore, FFM and skeletal muscle mass index (SMI) showed positive association with serum uric acid level and BMD at three sites, with statistical significance. An increase in serum uric acid level was associated with a lower risk of abnormal BMD after adjusting for confounders including FFM and SMI.

Conclusion

Serum uric acid level was positively associated with BMD at three sites and had a protective effect against abnormal BMD after adjusting for multiple confounders, including FFM and SMI, in men aged ≥ 50 years.

Sex Difference in the Associations among Obesity-Related Indices with Hyperuricemia in a Large Taiwanese Population Study

Hyperuricemia has been linked with the development of diabetes, gout, kidney, and cardiovascular diseases. Although obesity is associated with hyperuricemia, data on sex differences in this association are scarce. Therefore, this study was conducted to explore sex differences in the correlations among various indices of obesity with hyperuricemia in Taiwan. Data were obtained from the Taiwan Biobank and included 122,067 participants. After excluding 179 participants with missing data, the remaining 121,888 participants (men: 43,790; women: 78,098) were enrolled. The prevalence rates of hyperuricemia (defined as serum uric acid >7.0/6.0 mg/dL in men/women) were 29.8% and 13.6%, respectively (p < 0.001). Multivariable analysis revealed high values of body shape index (ABSI), waist-to-height ratio (WHtR), waist-hip ratio (WHR), lipid accumulation product (LAP), conicity index (CI), visceral adiposity index (VAI), body adiposity index (BAI), abdominal volume index (AVI), body mass index (BMI), and body roundness index (BRI) were significantly associated with hyperuricemia in both the male and female participants (all p < 0.001). The interactions between sex and all 10 of these indices were significant (all p < 0.001) for hyperuricemia. In men, LAP had the highest area under the curve (0.669), followed by BMI (0.655), VAI (0.645), AVI (0.642), BRI (0.640), WHtR (0.633), BAI (0.605), WHR (0.599), CI (0.574), and ABSI (0.510). In women, LAP also had the highest area under the curve (0.754), followed by BMI (0.728), VAI (0.724), WHtR (0.721), BRI (0.720), AVI (0.713), WHR (0.676), BAI (0.673), CI (0.626), and ABSI (0.544). In conclusion, obesity-related indices were associated with hyperuricemia in this large Taiwanese study, and sex differences were found in these associations, with stronger associations in women than in men.

Prevalence and influencing factors of hyperuricemia in middle-aged and older adults in the Yao minority area of China: a cross-sectional study

Hyperuricemia (HUA) endangers human health, and its prevalence has increased rapidly in recent decades. The current study investigated HUA's prevalence and influencing factors in Gongcheng, southern China. A cross-sectional investigation was conducted; 2128 participants aged 30-93 years were included from 2018 to 2019. Univariate and multivariate logistic regression models were used to screen HUA variables. A Bayesian network model was constructed using the PC algorithm to evaluate the association between influencing factors and HUA. The prevalence of HUA was 15.6% (23.2% in men, 10.7% in women). After screening the variables using a logistic regression analysis model, fatty liver disease (FLD), dyslipidemia, abdominal obesity, creatinine (CREA), somatotype, bone mass, drinking, and physical activity level at work were included in the Bayesian network model. The model results showed that dyslipidemia, somatotype, CREA, and drinking were directly related to HUA. Bone mass and FLD were indirectly associated with HUA by affecting the somatotype. The prevalence of HUA in Gongcheng was high in China. The prevalence of HUA was related to somatotype, drinking, bone mass, physical activity level at work, and other metabolic diseases. A good diet and moderate exercise are recommended to maintain a healthy somatotype and reduce the prevalence rate of HUA.

Trabecular Bone Score Significantly Influences Treatment Decisions in Secondary Osteoporosis

The trabecular bone score (TBS) can be determined in addition to the Dual Energy X-ray Absorptiometry (DXA) for bone mineral density (BMD) measurement to diagnose, evaluate, and stratify bone loss and decide on appropriate treatment in patients at risk. Especially in patients with secondary osteoporosis, TBS detects restricted bone quality. To investigate the influence of an additional evaluation of TBS on patients' treatment strategy decisions, we enrolled 292 patients, with a high proportion of patients with secondary osteoporosis, from one outpatient unit over one year. Patients eligible for BMD measurement had the option to opt-in for TBS measurement. We analyzed demographic data, leading diagnoses, bone metabolism parameters, and results of BMD and TBS measurements. More than 90% of patients consented to TBS measurement. TBS measurement influenced the decision in approximately 40% of patients with a treatment indication for anti-osteoporotic drugs. We demonstrate that depending on the underlying disease/risk spectrum, 21-25.5% of patients had an unremarkable BMD measurement with poor bone quality shown in the TBS measurement. In patients with secondary osteoporosis, the use of TBS supplementary to DXA seems useful to better assess fracture risk and, thus, to initiate therapy for osteoporosis in these patients in time.

Association and Interaction between Heavy Metals and Hyperuricemia in a Taiwanese Population

The prevalence of hyperuricemia in Taiwan is high, and hyperuricemia has been associated with a risk of developing several diseases. Although the traditional risk factors for hyperuricemia are well known, the relationship between heavy metals and hyperuricemia is still undefined. Therefore, the aim of this study was to investigate the relationship between hyperuricemia and heavy metals. A total of 2447 participants (977 males and 1470 females) residing in southern Taiwan were enrolled, and levels of the following heavy metals were measured: lead in blood, and nickel, chromium, manganese, arsenic (As), copper, and cadmium in urine. Hyperuricemia was defined as a serum uric acid level greater than 7.0 mg/dL (416.5 μmol/L) in men and 6.0 mg/dL (357 μmol/L) in women. The participants were divided into two groups: those without hyperuricemia (n = 1821; 74.4%) and those with hyperuricemia (n = 626; 25.6%). Multivariate analysis showed that only high urine As (log per 1 μg/g creatinine; odds ratio, 1.965; 95% confidence interval, 1.449 to 2.664; p < 0.001), young age, male sex, high body mass index, high hemoglobin, high triglycerides, and low estimated glomerular filtration rate were significantly associated with hyperuricemia. In addition, the interactions between Pb × Cd (p = 0.010), Ni × Cu (p = 0.002), and Cr × Cd (p = 0.001) on hyperuricemia were statistically significant. Increasing levels of Pb and Cr yielded an increased prevalence of hyperuricemia, and the effect was progressively greater for increasing Cd. Moreover, increasing levels of Ni yielded an increased prevalence of hyperuricemia, and the effect was progressively greater for increasing Cu. In conclusion, our results show that high urine As is associated with hyperuricemia, and some interactions of heavy metals on hyperuricemia are noted. We also found that young age, male sex, high BMI, high hemoglobin, high triglycerides, and low eGFR were significantly associated with hyperuricemia.

Association between Serum Uric Acid Levels and Bone Mineral Density in Taiwanese Elderly Population

Osteoporosis is a progressive metabolic bone disorder characterised by a decline in bone mineral density (BMD). Some previous studies have reported a controversial relationship between uric acid and osteoporosis. This cross-sectional study aimed to assess the association between serum uric acid levels and BMD in older adults from Taiwan. Data from participants aged ≥ 60 years were collected from 2008 to 2018. Furthermore, the participants were classified based on uric acid level quartiles. Regression models were used to assess the association between uric acid levels and bone health, including BMD values and risk of at least osteopenia. Crude and adjusted models of potential confounders, including age, sex and body mass index (BMI), were used. Compared with the first quartile of uric acid levels, the odds ratios for osteoporosis decreased in the higher uric acid level groups after adjustment for age, sex and BMI. The boxplot analysis showed that BMD values were higher in the groups with higher uric acid levels; moreover, the results of the multivariable linear regression model showed a consistent pattern. Notably, uric acid levels were positively correlated with BMD values. Higher uric acid levels in the elderly population might decrease the risk of at least osteopenia. As opposed to the anti-hyperuricemic policy for younger adults with a relatively lower risk of osteoporosis, BMD evaluation and urate-lowering therapy, goal adjustments should be considered for older adults with lower uric acid levels.

Synergetic Association between Anemia and Hyperuricemia on New-Onset Chronic Kidney Disease in a Large Taiwanese Population Follow-Up Study

The incidence of chronic kidney disease (CKD) is increasing worldwide; however, the association between CKD and anemia and hyperuricemia has yet to be clarified. In addition, whether anemia and hyperuricemia only influence renal damage in combination with other comorbidities or whether they are direct causative factors is also controversial. Therefore, the aim of this longitudinal study was to investigate these issues in a large Taiwanese cohort. We enrolled 26,631 participants from the Taiwan Biobank (TWB) after excluding those with CKD at the baseline, all of whom had follow-up data for a median of 4 years. In this study, CKD was defined as an estimated glomerular filtration rate < 60 mL/min/1.73 m2, incident new-onset CKD was defined as the development of CKD during follow-up, anemia was defined as a hemoglobin level <13 mg/dL in males and <12 mg/dL in females, and hyperuricemia was defined as a serum uric acid (UA) level >7 mg/dL in males and >6 mg/dL in females. The participants were divided into four groups according to whether or not they had anemia and hyperuricemia. Multivariable analysis showed that low hemoglobin (per 1 g/dL; odds ratio [OR], 0.760; p < 0.001) and high serum UA (per 1 mg/dL; OR, 1.444; p < 0.001) in model 1 and anemia (OR, 2.367; p < 0.001) and hyperuricemia (OR, 2.516; p < 0.001) in model 2 were significantly associated with new-onset CKD. Furthermore, compared to the group without anemia or hyperuricemia, the groups with anemia without hyperuricemia (OR, 2.502; p < 0.001), without anemia with hyperuricemia (OR, 2.559; p < 0.001), and with anemia and hyperuricemia (OR, 5.505; p < 0.001) were significantly associated with new-onset CKD. There was a significant interaction between hemoglobin and serum UA and new-onset CKD (p < 0.001). In conclusion, we found that anemia and hyperuricemia were associated with new-onset CKD, respectively, and also had a synergetic effect on new-onset CKD.

Associations of Liver Function Parameters with New-Onset Hyperuricemia in a Large Taiwanese Population Study

Hyperuricemia is the chief cause of gout and has been linked with hypertension, cardiovascular and renal disease, diabetes and metabolic syndrome. Liver with the highest protein expression of xanthine oxidase, the main enzyme responsible for uric acid formation, is the primary site of uric acid biosynthesis. However, there are few studies that examine the association between liver function and new-onset hyperuricemia. Hence, using the Taiwan Biobank dataset, we aimed to explore the capability of liver function parameters, including gamma-glutamyl transferase, total bilirubin, albumin, alanine aminotransferase and aspartate aminotransferase in association with the subsequent development of hyperuricemia. We analyzed 21,030 participants without hyperuricemia at baseline. Hyperuricemia was defined as a uric acid concentration > 6.0 mg/dL in women or >7.0 mg/dL in men. New-onset hyperuricemia was defined as participants without baseline hyperuricemia having developed hyperuricemia upon subsequent exam. Overall, 1804 (8.6%) of the study subjects developed new-onset hyperuricemia. After multivariable analysis, significant associations were found between the male sex (odds ratio [OR], 4.412; p < 0.001), high values of systolic blood pressure (SBP) (OR, 1.006; p = 0.012), body mass index (BMI) (OR, 1.064; p < 0.001), fasting glucose (OR, 1.005; p < 0.001), triglycerides (OR, 1.001; p = 0.003), uric acid (OR, 5.120; p < 0.001), low values of estimated glomerular filtration rates (eGFR) (OR, 0.995; p < 0.001), total bilirubin (OR, 0.616; p < 0.001) and new-onset hyperuricemia. The cutoff level of total bilirubin, according to the Youden index, of receiver operating characteristic curve for identifying new-onset hyperuricemia was 0.65 mg/dL. Low total bilirubin was defined as ≤0.65 mg/dL. After multivariable analysis, we found a significant association between low total bilirubin level (≤0.65 mg/dL) (OR = 0.806; p < 0.001) and new-onset hyperuricemia. Our present study demonstrated that in addition to male sex, high SBP, BMI, fasting glucose, triglycerides, and uric acid and low eGFR, the serum’s total bilirubin levels were negatively associated with new-onset hyperuricemia in a large Taiwanese cohort.

Sex Difference in the Associations among Hyperuricemia with New-Onset Chronic Kidney Disease in a Large Taiwanese Population Follow-Up Study

The global prevalence and incidence of chronic kidney disease (CKD) continue to increase. Whether hyperuricemia is an independent risk factor for renal progression and whether there are sex differences in the relationships between serum uric acid (UA) and a decline in renal function are unclear. Therefore, in this longitudinal study, we aimed to explore these relationships in a large cohort of around 27,000 Taiwanese participants in the Taiwan Biobank (TWB), and also to identify serum UA cutoff levels in men and women to predict new-onset CKD. A total of 26,942 participants with a median 4 years of complete follow-up data were enrolled from the TWB. We excluded those with CKD (estimated glomerular filtration rate <60 mL/min/1.73 m2) at baseline (n = 297), and the remaining 26,645 participants (males: 9356; females: 17,289) were analyzed. The participants who developed CKD during follow-up were defined as having incident new-onset CKD, and those with a serum UA level >7 mg/dL in males and >6 mg/dL in females were classified as having hyperuricemia. After multivariable analysis, hyperuricemia (odds ratio [OR], 2.541; 95% confidence interval [CI], 1.970−3.276; p < 0.001) was significantly associated with new-onset CKD. Furthermore, in the male participants (n = 9356), hyperuricemia (OR, 1.989; 95% CI, 1.440−2.747; p < 0.001), and quartile 4 of UA (vs. quartile 1; OR, 2.279; 95% CI, 1.464−3.547; p < 0.001) were significantly associated with new-onset CKD, while in the female participants (n = 17,289), hyperuricemia (OR, 3.813; 95% CI, 2.500−5.815; p < 0.001), quartile 3 of UA (vs. quartile 1; OR, 3.741; 95% CI, 1.250−11.915; p = 0.018), and quartile 4 of UA (vs. quartile 1; OR, 12.114; 95% CI, 14.278−34.305; p < 0.001) were significantly associated with new-onset CKD. There were significant interactions between hyperuricemia and sex (p = 0.024), and quartiles of serum UA and sex (p = 0.010) on new-onset CKD. Hyperuricemia was associated with new-onset CKD in the enrolled participants, and the interactions between hyperuricemia and sex were statistically significant. Hyperuricemia was more strongly associated with new-onset CKD in the women than in the men.

Influence of occupational exposure on hyperuricemia in steelworkers: a nested case-control study

BACKGROUND

Occupational exposure may be associated with an increased risk of developing hyperuricemia. This study sheds lights on the association between occupational exposure and hyperuricemia in steelworkers.

METHOD

A nested case-control study was conducted within a cohort of workers in steel companies to explore the association between occupational exposure and hyperuricemia. The case group consisted of a total of 641 cases of hyperuricemia identified during the study period, while 641 non-hyperuricemia subjects with the same age and gender distribution were randomly selected from the cohort as the control group.

RESULTS

The incidence rate of hyperuricemia among workers in the steel company was 17.30%, with an incidence density of 81.32/1,000 person-years. In comparison to the reference group, the risks of developing hyperuricemia for steelworkers undergoing ever shifts, current shifts, heat exposure, and dust exposure were 2.18 times, 1.81 times, 1.58 times and 1.34 times higher respectively. The odds ratios (ORs) and 95% confidence intervals (CIs) were 1.87(1.12-3.13) and 2.02(1.21-3.37) for the cumulative number of days of night work at 0-1,972.80 and ≥ 1,972.80 (days), respectively. Compared to the group with the cumulative heat exposure of 0 (°C/year), the ORs (95% CI) for the risk of developing hyperuricemia in the groups with the cumulative heat exposure of 0-567.83 and ≥ 567.83 (°C/year) were 1.50(1.02-2.22) and 1.64(1.11-2.43), respectively. The OR (95% CI) for the risk of developing hyperuricemia was 1.56(1.05-2.32) at the cumulative dust exposure of ≥ 30.02 (mg/m³/year) compared to that at the cumulative dust exposure of 0 (mg/m³/year). Furthermore, there was a multiplicative interaction between heat exposure and dust exposure in the development of hyperuricemia.

CONCLUSION

Shift work, heat, and dust are independent risk factors for the development of hyperuricemia in steelworkers. Additionally, there is a multiplicative interaction between heat exposure and dust exposure in the development of hyperuricemia. Interventions for shift work, heat and dust may help to reduce the incidence rate of hyperuricemia and improve the health of steelworkers.