Relationship between ideal cardiovascular health score and perioperative acute kidney injury: A case‐control study

Abstract Background Maintaining ideal cardiovascular health scores (CHS) may indirectly contribute to reducing the risk of perioperative acute kidney injury (AKI), which has never been explored previously. In this study, we aimed to explore the relationship between CHS and AKI and provide new ideas for AKI prevention and treatment. Methods We examined the effects of CHS on the occurrence of AKI among 2783 participants from the Kailuan study, who received general anesthesia during noncardiac surgery from 2016 to 2020. The odds ratios (ORs) and 95% confidence intervals (95% CIs) for AKI were calculated by using the logistic regression. Results Among 2783 participants 187 were diagnosed with perioperative AKI. We found an inverse relationship between the CHS scores and the risk of AKI. Participants with CHS score ≥ 10 had 57% decreased risk of AKI (OR = 0.43, 95% CI = 0.23, 0.79), compared with participants with CHS score ≤ 7, especially in men (OR = 0.39, 95% CI: 0.20, 0.76). In addition, participants who never smoked, exercised frequently, and had normal blood pressure had decreased risk of AKI, with corresponding ORs (95% CIs) of 0.66 (0.47, 0.91), 0.73 (0.60, 0.92), and 0.46 (0.28, 0.75), respectively. Conclusions CHS was strongly associated with the risk of perioperative AKI, and higher CHS scores were associated with a lower risk of AKI. Further research is needed to explore the long‐term effects of achieving and maintaining an ideal CHS on AKI risk.

Between 2016 and 2021, 2983 participants in the Kailuan Study received general anesthesia during noncardiac surgery.We excluded 200 participants for whom CHS data were not available, and a total of 2783 participants were included in this study (Supporting Information: Figure S1).

| Collection of clinical data and relevant definitions
For details on the epidemiological indicators, anthropometric measurements, and biochemical indicator tests evaluated in this study, please refer to prior literature published by our research team. 12,13The general clinical data of the selected individuals were collected through questionnaire surveys, and the information included smoking status, physical exercise, salt intake, any histories of diabetes, hypertension, abnormal blood lipid levels, heart failure, and medication history.Smoking was defined as smoking at least one cigarette/day on average over the past year, and drinking was defined as consuming at least 100 mL of hard liquor (with an alcohol content of 50% or more) per day on average over the past year, continuously, for at least 1 year.Individuals who had quit smoking or drinking for less than 1 year were still considered smokers or drinkers.Regular physical exercise was defined as exercising at least three times a week, with each session lasting at least 30 minutes, while occasional physical exercise was defined as exercising 1-2 times/week, with each session lasting at least 30 minutes.
Anthropometric and biochemical indicators of the selected individuals were collected from medical examination records.The BMI was calculated as BMI = weight/height 2 (kg/m 2 ).
Blood pressure in the right brachial artery was measured using a calibrated mercury sphygmomanometer.Systolic blood pressure (SBP)   and diastolic blood pressure (DBP) were determined using the first and fifth Korotkoff sounds, respectively.Three consecutive measurements were taken, with 1-2 minutes between each measurement, and the average value was recorded.For biochemical indicator testing, fasting (at least 8 hours) blood samples (5 mL) were collected from the median cubital vein on the day of the medical examination.A Hitachi 7600 biochemical analyzer was used for standardized testing.The main indicators included fasting blood glucose (FBG), TC, triglycerides, C-reactive protein (CRP), and other measures.
Fluid transfusion volume, blood transfusion volume, urinary volume, bleeding volume, anesthesia time, intraoperative blood pressure, operation levels, and ASA Physical Status Classification System scores were obtained from the intraoperative anesthesia records.

| CHS calculation and categorization
Each of the seven cardiovascular health behavior factors was assigned a score of two points for ideal, one point for moderate, and zero points for poor. 15The overall CHS value represents the total score of the seven items.Based on CHS, the selected population was divided into three groups: CHS ≤ 7 group, 8 ≤ CHS ≤ 9 group, and CHS ≥ 10 group.

| Diagnosis of perioperative AKI
According to current KDIGO guidelines, 6 AKI is diagnosed based on two functional markers: serum creatinine increase and urine output decrease.Considering serum creatinine levels, AKI presents as a sudden increase in serum creatinine by at least 0.3 mg/dL (26.5 µmol/L) within 48 hours or an increase in serum creatinine to at least 1.5 times the baseline value, which is known or presumed to have occurred within the past 7 days.Considering urine output, AKI presents as decreased urine output, also known as oliguria, which is defined as urine output of less than 0.5 mL/kg/h for at least 6 hours.However, it is important to note that urine output alone may not be a reliable indicator in some individuals, such as in patients taking diuretics or those with pre-existing kidney disease.

| Statistical analysis
Health examination data were imported by trained personnel and uploaded through the network to the computer center at Kailuan General Hospital, into an Oracle 10.2 database.Statistical analyses were performed using SAS software (SAS Institute) version 9.4.
Normally distributed continuous data are presented as mean ± standard deviation, and comparisons among multiple groups were analyzed using one-way analysis of variance.Skewed distributed continuous data are presented as median (interquartile range), and comparisons were conducted using a nonparametric test (Kruskal-Wallis test).
Categorical data are presented as frequencies (percentages), and comparisons were performed using the χ 2 test.Restricted cubic spline curves were used to calculate the continuous form of CHS and the dose-response relationship with the odds ratio (OR) of AKI.

Multivariable logistic regression models were used to analyze the influence of the CHS group on the ORs (95% confidence interval [CI])
of AKI, and the ORs of each CHS metric for AKI were further analyzed.
Propensity score matching was applied to match the AKI and non-AKI groups, followed by multivariate logistic regression analysis to reduce the impact of confounding factors on the results.Subgroup analyses on the relationships were also conducted on the variables of age (median, <63 vs. ≥63 years) and sex.Sensitivity analysis was performed by excluding participants who underwent renal surgery, followed by multivariate logistic regression analysis, to minimize the influence of this subgroup on the results.Differences with p < .05(two-sided) were considered statistically significant.

| General clinical characteristics
Our study included a final population of 2783 participants, with 772, 1035, and 976 individuals in the CHS score ≤ 7 group, 8 ≤ CHS score ≤ 9 group, and CHS score ≥ 10 group, respectively.Age, SBP, DBP, FBG, BMI, TC, CRP, hemoglobin (Hb), fluid transfusion volume, blood transfusion volume, urinary volume, bleeding volume, and anesthesia time differed significantly among the three groups (all p < .05;Table 1).The percentages of men, hypertension, diabetes, chronic heart disease (CHD), stroke, intraoperative hypotension, physical activity, salt intake, smoking, alcohol consumption, and ASA Physical Status Classification System differed between the groups (all p < .05;Table 1).We further divided the subjects according to whether they had AKI and explored the general clinical information of the two groups (Supporting Information: Table S1).

| Relationship between CHS levels and AKI
Among the 2783 participants in the Kailuan study who received general anesthesia during noncardiac surgery from 2016 to 2021.A total of 187 were diagnosed with perioperative AKI.The inverse relationship between the CHS scores and AKI risk is shown in  95% CI: 0.23, 0.98), as did the male population (OR = 0.39, 95% CI: 0.20, 0.76).

| Sensitivity analysis and CHS components
In the sensitivity analysis, participants who underwent kidney surgery were excluded to eliminate the possible effects of kidney surgery on the primary outcome.We further used propensity score matching to adjust for imbalances in covariates between patients with AKI and the non-AKI population, and similar results were obtained for the primary findings (Supporting Information: Tables S2 and S3).We further analyzed the relationship between each CHS component and AKI risk (

| DISCUSSION
The identification of modifiable risk factors is crucial for AKI prevention and management.In the current study, we found that CHS scores are strongly associated with the risk of perioperative AKI, with higher CHS scores associated with a lower risk of AKI, especially in men.In addition, the CHS components, including nonsmoking status, exercise, and normal blood pressure, were associated with a lower risk of AKI.These findings provide a theoretical basis and clinical evidence for preventing perioperative AKI.
The CHS score is a composite measure of cardiovascular health that is based on several modifiable risk factors, which include smoking status, BMI, physical activity, diet, blood pressure, blood glucose, and cholesterol levels.While few studies have investigated the association between CHS and AKI, numerous studies have consistently shown that individuals with a higher CHS have a significantly lower risk of several health outcomes, including cardiovascular disease 16,17 (coronary artery disease, stroke, and heart failure), all-cause mortality, 18 metabolic health 19 (obesity, type 2 diabetes, and metabolic syndrome), and cognitive function. 20In 2010, the AHA established ambitious goals to enhance the cardiovascular health of the population by 20% and reduce mortality from cardiovascular diseases and stroke by 20% by the year 2020.F I G U R E 2 Subgroup analysis of the relationship between CHS and AKI risk.AKI, acute kidney injury; CHS, cardiovascular health scores; CI, confidence interval; HR, hazard ratio.
Achieving these goals necessitates the development of new strategic approaches to cardiovascular health promotion and disease prevention using the AHA's research, clinical results, public health policies, and patient advocacy initiatives for the coming decade and beyond.
In our study, we investigated the association between each CHS component and the occurrence of perioperative AKI.Our findings revealed that nonsmoking status, regular physical activity, and optimal blood pressure were significantly associated with a reduced risk of developing AKI during the perioperative period.Notably, smoking has previously been identified as a risk factor for AKI. 22rmful chemicals present in tobacco smoke can lead to endothelial dysfunction and inflammation, which affects the blood vessels and impairs kidney function. 23Smoking also causes vasoconstriction, reduces renal blood flow, and promotes blood clot formation, which can contribute to kidney damage. 24Additionally, smoking has been linked to increased oxidative stress and the release of inflammatory markers that further exacerbate kidney injury. 25The relationship between blood pressure and AKI can be explained by several Maintaining an ideal CHS can potentially decrease the risk of perioperative AKI through several mechanisms, as follows.First, maintaining an ideal CHS provides a healthy cardiovascular system, 27 which ensures optimal blood flow to all organs, including the kidneys.
Good blood flow helps maintain an adequate oxygen and nutrient supply to the kidneys and reduces the risk of kidney injury.Conversely, individuals with compromised cardiovascular health may have reduced blood flow to the kidneys, making them more susceptible to AKI.
Second, maintaining an ideal CHS lowers the risk of ischemia. 28chemia refers to an inadequate blood supply to tissues or organs.
During surgery, there can be instances of reduced blood flow to the kidneys due to various factors, such as changes in blood pressure or the use of certain medications.Having an ideal CHS, which includes factors such as blood pressure control and regular exercise, can minimize the risk of ischemia-related kidney injury.Third, maintaining an ideal CHS reduces inflammation. 29Surgery triggers an inflammatory response in the body that contributes to kidney injury.Furthermore, a healthy cardiovascular system is associated with low systemic

| CONCLUSIONS
The results of this study suggest that CHS is strongly associated with the risk of perioperative AKI, with higher CHS scores being associated with a lower risk of AKI, especially in men.Promoting and maintaining ideal cardiovascular health, as measured by the CHS, should be a public health priority.Strategies that aim to promote cardiovascular health should focus on lifestyle modifications, risk factor management, and promoting an awareness of CHS metrics.
Further research is required to explore the long-term effects of achieving and maintaining an ideal cardiovascular health status on various health outcomes.

Figure 1 .
Figure 1.After adjustments were made for age, sex, operation levels, history of stroke and CHD, anesthesia time, drinking status, intraoperative hypotension, CRP, Hb, fluid and blood transfusion volume, urinary volume, bleeding volume, and ASA Physical Status Classification System, participants with CHS score ≥ 10 had 57% decreased ORs of AKI (OR = 0.43, 95% CI = 0.23, 0.79), compared with participants with CHS score ≤ 7 (Table2).As shown in Figure2, inflammation.By adhering to a healthy lifestyle, including a balanced diet and regular exercise, individuals can reduce chronic inflammation and potentially mitigate inflammatory responses during surgery, thereby lowering the risk of AKI.Fourth, an ideal CHS minimizes nephrotoxic exposure.Certain medications and substances used during surgery, such as contrast agents and anesthetics, can have nephrotoxic effects, potentially leading to AKI.However, individuals with ideal cardiovascular health may have fewer comorbidities and a reduced need for certain medications, which minimizes their exposure to nephrotoxic substances and consequently decreases their risk of AKI.Fifth, maintaining an ideal CHS allows optimal fluid balance, which is crucial for kidney health.Patients with ideal cardiovascular health are more likely to have a well-regulated fluid status, which can help prevent fluid overload or dehydration, both of which can contribute to kidney injury during surgery.Overall, perioperative AKI is a significant clinical problem with a complex pathogenesis and multiple risk factors.Further research is required to improve our understanding of the underlying mechanisms, develop more effective preventive strategies, and identify new treatments for this serious complication.This study represents a pioneering analysis of the association between CHS and AKI, and our findings shed new light on the prevention and management of perioperative AKI.The notable strengths of this study include substantial sample size, the inclusion of numerous relevant covariates, and the application of multiple statistical methods, including propensity scores.It is also important to acknowledge the limitations of this study.First, the study did not incorporate several novel markers of kidney injury, for example, neutrophil gelatinase-associated lipocalin,30 which could have provided additional insights into the relationship between CHS and AKI.These markers may include urinary biomarkers or imaging techniques that can accurately assess renal function and structural changes.Second, it is important to acknowledge that the Kailuan community primarily consists of industrial laborers, which may lead to an imbalance in the distribution of sexes within the study population.However, it is noteworthy that the researchers conducted separate statistical analyses for both sexes, which helped to mitigate the potential impact of this imbalance on the study results.Third, we only used CHS data from a single measurement.CHS may change over time, which may have led to misgrouping of the population.Future studies should focus on long-term CHS and the impact of changes on health outcomes.

Table 2
Baseline characteristics of the study population stratified by CHS scores.

Table 3
).After adjusting for age, sex, operation level, history of stroke and CHD, anesthesia time, drinking status, intraoperative hypotension, CRP, Hb, fluid and blood transfusion volume, urinaryT A B L E 1 (Continued) 21 The ORs (95% CI) of CHS groups for the AKI risk.Adjustments were made for age, sex, operation levels, history of stroke and chronic heart disease, anesthesia time, drinking status, intraoperative hypotension, C-reactive protein, HGB, fluid and blood transfusion volume, urinary volume, bleeding volume, and ASA physical status classification system.Abbreviations: AKI, acute kidney injury; CHS, cardiovascular health scores; CI, confidence interval; HGB, hemoglobin; OR, odds ratio.
T A B L E 2 The ORs (95% CI) of each CHS component for the AKI risk.Results presented with bold valued were statistically significant with all p value < 0.05.Adjustments were made for age, sex, operation levels, history of stroke and chronic heart disease, anesthesia time, drinking status, intraoperative hypotension, C-reactive protein, HGB, fluid and blood transfusion volume, urinary volume, bleeding volume, ASA physical status classification system, and all cardiovascular health score components.