Smooth Test Research Articles

Association between a body shape index and bone mineral density in US adults based on NHANES data

The relationship between a body shape index (ABSI) and bone mineral density (BMD) remains uncertain, prompting further investigation. This study aims to elucidate the association between ABSI and BMD using data from the 2011–2018 National Health and Nutrition Examination Survey (NHANES), involving participants aged 20–60. ABSI was calculated using the formula: ABSI = 1000 × waist circumference (m)×weight (kg)−2/3×height (m)5/6. The analysis employed weighted multiple linear regression, smooth curve fitting, stratified analysis, and interaction tests to explore the relationship between ABSI and total BMD. The study included 10,291 participants, with a mean age of 39.11 ± 10.77 years, and 49.20% were women. The average ABSI was 80.21 ± 1.50. Total BMD, thoracic spine BMD, lumbar spine BMD, and pelvis BMD were measured, with mean values of 0.82 ± 0.11 g/cm², 1.03 ± 0.15 g/cm², and 1.24 ± 0.16 g/cm2, respectively. A negative correlation between ABSI and total BMD was observed. In the fully adjusted model, individuals in the highest ABSI quartile had total BMD levels 0.045 g/cm² lower than those in the lowest quartile. Interaction tests showed a consistent association between ABSI and total BMD across subgroups, with variations in sex and BMI. This analysis of NHANES data confirms a persistent negative association between ABSI and BMD, suggesting that ABSI could be useful in osteoporosis prevention and diagnosis.

Nonlinear association between the serum uric acid-to-creatinine ratio and all cause mortality in patients with hypertension: a ten-year cohort study using the NHANES database

The serum uric acid-to-creatinine ratio (UCR) may be a simple method for assessing xanthine oxidase overactivation, which may contribute to an increase in serum uric acid production and oxidative stress. In this study, we investigated the nonlinear association between the UCR and long-term mortality in patients with hypertension. Data were acquired from the National Health and Nutrition Examination Survey database, and a total of 11,346 patients with hypertension were included. We explored the nonlinear link between the UCR and all-cause mortality via spline smoothing, threshold saturation, and log-likelihood ratio tests. The results were validated through a competing risk model. A nonlinear pattern emerged between the UCR and all-cause mortality in hypertensive patients, with an inflection point at 4.3. Below this point, an increased UCR was associated with a decreased mortality risk (OR = 0.80, 95% CI: 0.68–0.94, P = 0.008), whereas above this point, the risk increased (OR = 1.21, 95% CI: 1.07–1.36, P = 0.004). The competing risk model yielded similar findings for cardiovascular and chronic kidney disease-related deaths. In patients with hypertension, the UCR nonlinearly predicted all-cause mortality, with a notable inflection at 4.3. These findings suggest that the UCR is a valuable prognostic indicator for assessing long-term outcomes in patients with hypertension.

Application of an Instability‐Based Fracture Model for Prediction of Crack Initiation in Modified 9Cr–1Mo Steel

ABSTRACTDuctile fracture of modified 9Cr–1Mo steel was investigated using smooth and notched bar tension tests. Round and flat notched specimens with varying notch acuity ratio were used to investigate the influence of stress state on the fracture strain. Simulations of the experiments were performed using the extended finite element method, together with an instability‐based crack initiation criterion based on the micromechanics of void coalescence. The parameters in the plasticity model were determined using smooth bar tension tests, whereas the void nucleation parameters were calibrated from experiments on a shallow‐notched specimen. Subsequently, the load–deflection responses and strain to crack initiation have been predicted for round and flat notched specimens with various notch acuities, and central notched specimens with notches oriented at various angles to the loading axis. Using a single set of parameters, the model was able to quantitatively predict fracture in different specimen geometries encompassing a range of stress states.

Almost sharp Sobolev trace inequalities in the unit ball under constraints

We establish three families of Sobolev trace inequalities of orders two and four in the unit ball under higher order moments constraint, and are able to construct smooth test functions to show all such inequalities are almost optimal. Some distinct feature in almost sharp examples between the fourth order and second order Sobolev trace inequalities is discovered. This has been neglected in higher order Sobolev inequality case in [21]. As a byproduct, the method of our construction can be used to show the sharpness of the generalized Lebedev-Milin inequality under constraints.

The Effect of Prism Presentation Order on Near Vertical Fusional Vergence Ranges of Normal Young Adults.

Fusional vergence ranges (FVR) quantify the oculomotor system's ability to overcome heterophoria, playing a critical role in diagnosis and treatment.This study investigated the effect of prism order on near vertical FVR using the smooth and step methods. Normal participants were randomly assigned to either the smooth or step testing method and to Base-Up (BU, infravergence) first or Base Down (BD, supravergence) first prism type. After an hour, they crossed over tothe alternative testing method and prism-type. The mean of two consecutive measurements of break and recovery values for one eye in each of the 16 experimental conditions were compared using the Friedman test with post-hoc Bonferroni correction, and non-parametric Bland and Altman analysis. The mean break/recovery values of 27 participants (mean age: 22.5±2.0, range: 20-29, 20female) when BU or BD were measured first were BU: 4.20±1.15Δ/3.07±1.04Δand BD: 4.20±1.21Δ/3.00±0.96Δfor step, and BU: 4.31±0.98Δ/2.97±0.85Δand BD: 4.15±1.14Δ/2.70±0.87Δfor smooth methods, respectively. When measured second, they were BU: 3.74±1.02Δ/2.63±0.93Δand BD: 3.85±1.09Δ/2.64±1.06Δfor step, BU: 3.91±0.99Δ/2.73±0.93Δand BD: 3.81±1.04Δ/2.54±1.04Δ for smooth, respectively. The Friedman test found a significant effect of prism order on break values of the smooth (p<0.001) and step (p<0.02) methods, and recovery values of the step method (p<0.005), but post-hoc tests showed no significant differences. Mean differences were below 0.50Δindicating clinical insignificance. Unlike horizontal FVR, prism order does not affect near vertical FVR using the smooth and step. This simplifies clinical assessment and suggests that horizontal and vertical fusion systems may be treated as separate entities.

Vitamin C and suicidal ideation: A cross-sectional and Mendelian randomization study

BackgroundStudies have shown that a history of suicide attempts is associated with low levels of antioxidant vitamins. However, the specific relationship between vitamin C and suicidal ideation remains poorly understood. The purpose of this study is to investigate the effect of vitamin C on the development of suicidal ideation and to explore further the causal relationship using Mendelian randomization (MR). MethodsUsing the 2005–2018 National Health and Nutrition Examination Survey (NHANES) dataset, a comprehensive, cross-sectional, stratified survey of 28,623 participants aged 20 years and older was conducted. Suicidal ideation was assessed using item 9 of the Patient Health Questionnaire-9 (PHQ-9) item. The relationship between vitamin C and suicidal ideation was revealed by weighted multiple linear regression, smooth curve fitting, hierarchical analysis, and interaction test. To determine causality, MR was performed on vitamin C and suicidal ideation. ResultsIn cross-sectional studies, all models showed a negative association between vitamin C and suicidal ideation, with a 37 % reduction in the risk of suicidal ideation for each unit increase in vitamin C in the highest quartile in the fully adjusted model. The results of the subgroup analysis showed that the association between vitamin C and suicidal ideation was stable across gender, age, education, smoking status, and marital status. In the MR study, our bivariate model showed no significant causal relationship between vitamin C and the development of suicidal ideation. ConclusionsDietary vitamin C intake was negatively associated with the development of suicidal ideation. However, genetic evidence does not support causation of these associations.

Non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) and hypertension in American adults: a NHANES cross-sectional study.

The relationship between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) and hypertension remains uncertain, warranting further investigation. This study aims to elucidate the association between NHHR and hypertension. A comprehensive cross-sectional stratified survey involving 30,602 participants aged 20years and older was conducted using the National Health and Nutrition Examination Survey (NHANES) dataset from 2001 to 2018. NHHR was calculated as [total cholesterol (TC) - high-density lipoprotein cholesterol (HDL-C)]/HDL-C. The relationship between NHHR and hypertension was examined using weighted multiple linear regression, smooth curve fitting, hierarchical analysis, and interaction testing. The mean age of participants was 49.82 ± 17.64 years, with 15,266 women included. The average NHHR was 2.94 ± 0.56. A positive correlation between NHHR and hypertension was observed. Stratification of NHHR into quartiles, in the fully adjusted Model 3, revealed that individuals in the highest NHHR quartile had a 60% increased risk of hypertension for each unit increase in NHHR compared to those in the lowest quartile. Interaction tests indicated that the relationship between NHHR and hypertension remained consistent across subgroups, except for gender, age, education, and smoking status, which influenced this association. Analysis of NHANES data from 2001 to 2018 demonstrated a consistent positive association between NHHR and hypertension. NHHR may provide potential assistance in hypertension prevention and diagnosis.

Transmission Characteristics and Experiment of Hydraulic–Mechanical Transmission of Cotton Picker

To overcome the issue of unstable speed output encountered by cotton pickers operating in harsh environments and subject to frequent external load fluctuations, a hydraulic–mechanical transmission (HMT) for cotton pickers is proposed in this study. By analyzing the driving system of the cotton picker, a Lavira-based HMT scheme is developed. The matching characteristics of the HMT speed ratio are analyzed, a continuity and smoothness test of the speed ratio of the changing segment is carried out, and the influence law of smoothness of the HMT changing segment is discussed. The results show that the HMT system effectively satisfies the driving speed requirements for both field harvesting and road transportation of cotton pickers. The HMT speed ratio is continuously controllable and the design is reasonable. The HMT load torque and the oil pressure in the main oil circuit have a significant impact on the smoothness indicators of speed reduction and dynamic load. Additionally, the flow rate of the governor valve has a notable effect on the smoothness indicator of sliding friction power. However, the engine’s output speed has no significant influence on the HMT’s smoothness. This research can provide theoretical support for the development and design of cotton picker gearboxes and the transmission characteristics and experimental research of off-road vehicle gearboxes.

Sensorimotor tests in patients with neck pain and its associated disorders: a systematic review and meta-analysis

This systematic review aimed to synthesize the current evidence regarding neck sensorimotor testing in individuals with neck pain, assess the differences between neck pain groups and healthy controls, and recognize factors that might affect test results. We performed the data search using PubMed, Embase, PsycINFO, CINAHL, and Scopus databases. We used a two-step screening process to identify studies. Furthermore, we screened the reference lists for additional studies. Hedges g was used to present the difference between neck pain groups and asymptomatic individuals. We assessed the quality of the studies using the QUADAS tool. The final review included 34 studies, of which 25 were related to the joint position error test, four to the smooth pursuit neck torsion test and six to the balance test. Our meta-analysis showed poorer joint-position sense, oculomotor function, and wider postural sway in individuals with neck pain than healthy controls. The size of the difference between the groups seemed to be influenced by the intensity of the pain and the presence of dizziness. Therefore, it might be helpful in future studies to differentiate patients with neck pain into subgroups based on their symptom and demographic profiles to assess other factors that significantly affect cervical sensorimotor control.

The relationship between body roundness index and depression: A cross-sectional study using data from the National Health and Nutrition Examination Survey (NHANES) 2011–2018

BackgroundDepression is linked to obesity. The body roundness index (BRI) provides a more accurate assessment of body and visceral fat levels than the body mass index or waist circumference. However, the association between BRI and depression is unclear. Therefore, we investigated this relationship using the National Health and Nutrition Examination Survey (NHANES) database. MethodsIn this population-based cross-sectional study, data from 18,654 adults aged ≥20 years from the NHANES 2011–2018 were analyzed. Covariates, including age, gender, race/ethnicity, education level, marital status, poverty-income ratio, alcohol status, smoking status, hypertension, diabetes mellitus, cardiovascular disease, energy intake, physical activity, total cholesterol, and triglycerides were adjusted in multivariable logistic regression models. In addition, smooth curve fitting, subgroup analysis, and interaction testing were conducted. ResultsAfter adjusting for covariates, BRI was positively correlated with depression. For each one-unit increase in BRI, the prevalence of depression increased by 8 % (odds ratio = 1.08, 95 % confidence interval = 1.05–1.10, P < 0.001). LimitationsAs this was a cross-sectional study, we could not determine a causal relationship between BRI and depression. Patients with depression in this study were not clinically diagnosed with major depressive disorder. ConclusionBRI levels were positively related to an increased prevalence of depression in American adults. BRI may serve as a simple anthropometric index to predict depression.

Automatic Pricing and Replenishment Decision-Making for Vegetable Commodities Based on Seasonal Index Prediction Models

This study provides an in-depth analysis of the relationship between sales, pricing, and product categories to construct a predictive model designed to optimize replenishment decisions and maximize superstore profits. The study begins with data preprocessing, integrating data coded according to individual products, on which the model is built and solved. In the first part, descriptive statistical analysis and visualization revealed that the sales volume of each category showed a cluster-like distribution, which was affected by seasonal variations. Based on the time series smoothness test, it is initially judged that each individual product is a smooth series, and the smoothness of the series is verified by ADF test. In the second part, the correlation coefficients of the sales volume of each category and single product were calculated by using Spearman correlation analysis, and the results were presented through heat maps, which revealed the strong correlation between different categories. For the relational equation between total sales volume and cost-plus pricing, an autoregressive and least squares model was developed, with cost-plus pricing as the dependent variable and total sales volume as the independent variable. For the seasonal index prediction model, the total daily replenishment and pricing at future dates were predicted by calculating the seasonal index. The results show that the replenishment volume of flowers and leaves fluctuates greatly, and it is recommended that pricing and replenishment volume be adjusted in a timely manner according to the actual sales situation; cauliflower, aquatic roots and tubers, and eggplant are relatively stable, and they should be adjusted moderately according to the market demand; and chili peppers and edibles are on a downward trend, and it is recommended that replenishment volume be reduced in order to avoid the inventory backlog.

Development and application of wellbore flow assurance monitoring system for combustible ice production in deepwater

The commercial development of combustible ice, as the most promising strategy energy, requires not only efficient gas production technology but also a safe flow assurance system. For the depressurization development of combustible ice in the sea area, the issues of wellbore fluid carrying sand, hydrate re-formation in the wellbore, and instability of wellbore flow, are the key problems leading to flow obstacles in the wellbore and affecting the normal production. Therefore, some measures must be taken to effectively monitor and analyze the flow situation in the wellbore during the development of combustible ice in the sea. In this paper, a Wellbore Flow Assurance Monitoring System (WFAMS) is developed to display the fluid flow conditions in the wellbore in real-time during the gas hydrate production, including temperature, pressure, flow rate, the carrying sand amount, etc. Furthermore, the system is capable of online monitoring for potential plug risks, including sand plugs and hydrate blockages caused by gas hydrate formation, as well as assessing flow stability. Additionally, it can provide valuable information, such as production adjustment data and the required injection dosage of thermodynamic inhibitors to prevent hydrate formation. In the 2020 South China Sea production test, this system was used for depressurization production and successfully predicted wellbore flow conditions. This enabled field engineers to monitor flow risks and adjust production plans in a timely manner, ensuring smooth test progress.

Bending analysis of quasicrystal plates using adaptive radial basis function method

A novel mesh-free kernel method is presented for solving function interpolation problems and partial differential equations (PDEs). Despite the simplicity and accuracy of the radial basis function (RBF) method, two main difficulties have been identified: the selection of the scale or shape parameter and the ill-conditioning issue. To address these challenges, an effective condition number (ECN) strategy is proposed for the scale parameter selection, utilizing the ill-conditioning issue to minimize errors. The study demonstrates that this method performs exceptionally well with severely ill-conditioned matrices, making it suitable challenging engineering problems. However, when the problem is severely ill-conditioned, an accurate and efficient method for determining the minimal singular values used in the ECN formulation is required. To tackle this, we utilize an efficient algorithm called minsv, which specifically computes the minimal singular value. The significance of accurately computing the smallest singular value is demonstrated through two interpolation examples, involving non-smooth and smooth test functions with various RBFs and data points. Furthermore, the RBF method is applied to solve a quasicrystal problem, which presents a challenging engineering problem with four unknown parameters, and excellent results are obtained. Finally, we illustrate that using MATLAB’s svd function can potentially produce completely incorrect minimal singular values. The codes implemented are available at https://doi.org/10.24433/CO.8716692.v1.

Strain-Based damage model for ductile tearing simulation under combined tensile and shear modes

This paper proposes a strain-based damage model to simulate ductile tearing under combined tensile and shear modes. For tensile mode, the multiaxial fracture strain model depending only on the stress triaxiality is used, determined by analysing smooth bar tensile test and fracture toughness test data. For shear mode, a simple constant fracture strain model is used, determined by analysing smooth bar torsion test and torsion fracture test using a deep surface cracked cylinder specimen. The proposed damage model is applied to simulate circumferential surface cracked pipe made of SUS 304 under combined bending and torsion. Comparison with full-scale surface cracked pipe test data suggests that the use of the combined tensile and shear damage model with the linear interaction rule gives good and conservative prediction results.

Effect of Shock Absorber Friction on Vehicle Vertical Dynamics

&lt;div&gt;In order to efficiently predict and investigate a vehicle’s vertical dynamics, it is necessary to consider the suspension component properties holistically. Although the effects of suspension stiffness and damping characteristics on vertical dynamics are widely understood, the impact of suspension friction in various driving scenarios has rarely been studied in both simulation and road tests for several decades.&lt;/div&gt; &lt;div&gt;The present study addresses this issue by performing driving tests using a special device that allows a modification of the shock absorber or damper friction, and thus the suspension friction to be modified independently of other suspension parameters. Initially, its correct functioning is verified on a shock absorber test rig. A calibration and application routine is established in order to assign definite additional friction forces at high reproducibility levels.&lt;/div&gt; &lt;div&gt;The device is equipped in a medium-class passenger vehicle, which is driven on various irregular road sections as well as over single obstacles. For all tested road sections, a linear decrease of ride comfort in terms of specific relevant vertical objective values is found by increasing the friction force. This emphasizes a definite link between suspension friction and vertical vehicle body vibration, resulting in a negative impact on vertical ride comfort. However, the longitudinal vehicle body vibration is not significantly affected.&lt;/div&gt; &lt;div&gt;The relevance of friction in terms of transmitting the energy associated with road unevenness to the chassis in the frequency range of the chassis’ natural frequency is found to be remarkably high on smooth roads, and still considerably high on bumpy roads. The chassis and wheel resonance frequencies are significantly friction-dependent due to the damper’s slip or stick states. The results obtained from smooth road tests demonstrate the practical relevance of accurately considering friction for the given suspension type in terms of vertical ride comfort prediction.&lt;/div&gt;

Efficient data integration under prior probability shift.

Conventional supervised learning usually operates under the premise that data are collected from the same underlying population. However, challenges may arise when integrating new data from different populations, resulting in a phenomenon known as dataset shift. This paper focuses on prior probability shift, where the distribution of the outcome varies across datasets but the conditional distribution of features given the outcome remains the same. To tackle the challenges posed by such shift, we propose an estimation algorithm that can efficiently combine information from multiple sources. Unlike existing methods that are restricted to discrete outcomes, the proposed approach accommodates both discrete and continuous outcomes. It also handles high-dimensional covariate vectors through variable selection using an adaptive least absolute shrinkage and selection operator penalty, producing efficient estimates that possess the oracle property. Moreover, a novel semiparametric likelihood ratio test is proposed to check the validity of prior probability shift assumptions by embedding the null conditional density function into Neyman's smooth alternatives (Neyman, 1937) and testing study-specific parameters. We demonstrate the effectiveness of our proposed method through extensive simulations and a real data example. The proposed methods serve as a useful addition to the repertoire of tools for dealing dataset shifts.

Quantitative ultrasonic characterization of Ti-6Al-4V components with surface roughness

Ultrasonic immersion testing enables nondestructive characterization of material microstructure through quantitative linkages between wave propagation parameters and features of interest. However, accurate measurements of metrics such as wave speed and attenuation generally require smooth test samples to ensure the reflected wave packets are not distorted. Thus, rough surfaces are mechanically polished before ultrasonic testing, which compromises the nondestructive nature of the measurement, distorting the sample geometry and imparting local damage. This challenge is particularly salient with the advent of manufacturing processes, such as metal additive manufacturing, that result in rough samples that must be characterized for heterogeneities in their as-manufactured state. This work examines the influence of surface roughness on longitudinal wave speed and attenuation in wrought and additively manufactured Ti-6Al-4V specimens. Samples are measured in an ultrasonic immersion setup before and after mechanical polishing using varying transducer frequencies and focal profiles. The resulting data informs the error generated in ultrasonic measurements as a function of roughness parameters, thereby informing the sample preparation needed for desired precision levels. Lastly, new measurement protocols are explored to correct for the presence of surface irregularities in a point-by-point fashion. This work was supported by the Robert W. Young Award for Undergraduate Student Research.

The associations of two novel inflammation indexes, systemic immune-inflammation index (SII) and system inflammation response index (SIRI), with periodontitis: evidence from NHANES 2009-2014.

The research's goal is to look for any potential relationships between the systemic immune-inflammation index (SII) and the system inflammation response index (SIRI), along with inflammation indicators and the likelihood of periodontitis. Ten thousand two hundred eighty-two individuals in sum were determined to be eligible for this cross-sectional study from the National Health and Nutrition Examination Survey (NHANES) between 2009 and 2014. Multiple logistic regression, generalized additive model, smooth curve fitting, subgroup analysis, and interaction tests were done for analyzing the association between periodontitis and SII, SIRI, and other inflammatory indicators. The analysis, adjusted for population weighting, revealed that individuals with moderate/severe periodontitis had SII levels of 545.46 (95% CI (529.10, 561.82), P = 0.0044) and SIRI levels of 1.33 (95% CI (1.29, 1.37), P < 0.0001). In a fully adjusted multivariate logistic regression model, SII was not sensibly associated with moderate/severe periodontitis among the continuous and quartile Q1-Q4 groups (OR = 0.97, 95% CI (0.91, 1.02)). The continuous variable of SIRI (OR = 1.11, 95% CI (1.06, 1.17)) and the quartile Q4 group (OR = 1.58, 95% CI (1.28, 1.94)) had a deemed significant positive association with moderate to severe periodontitis. In addition, other inflammatory indicators, especially NLR, PPN, PLR, MLR, PC, NC, and MC were observed to be notably involved moderate/severe periodontist in this research. We explored the association between periodontitis and two novel comprehensive markers of inflammation (SII and SIRI). These inflammatory markers are expected to serve as tools to assist clinicians in diagnosing periodontitis.

Identifying changes in the distribution of income from higher‐order moments with an application to Australia

SummaryChanges in the distribution of income over time are identified based on an adjusted two‐sample version of the Neyman smooth test by using subsampling methods to approximate the sampling distribution of the test statistic when samples are not independent of each other. A range of Monte Carlo experiments show that the approach corrects for size distortions arising from dependent samples as well as generating monotonic power functions. Applying the approach to studying the distribution of income in Australia over the business cycle and the Global Financial Crisis, the empirical results highlight the importance of higher‐order moments and demonstrate that business cycles are not all alike as the relative strengths of higher‐order moments vary over phases of the cycle.

The association between plain water intake and periodontitis in the population aged over 45: a cross-sectional study based on NHANES 2009–2014

BackgroundNumerous studies have demonstrated the impact of beverage consumption on overall health and oral health. Specifically, high consumption of sugar-sweetened beverages and coffee has been associated with an increased risk of metabolic disorders and periodontitis. Conversely, high intake of plain water has been linked to various health benefits, including weight management and reduced energy intake. However, no previous studies have explored the potential association between plain water intake and the risk of periodontitis.ObjectivesOur objective was to investigate the relationship between plain water consumption and periodontitis in a middle-aged and elderly population.MethodsThe present cross-sectional study was conducted among participants aged ≥ 45 in the 2009–2014 National Health and Nutrition Examination Surveys. Multivariable regression analysis, subgroup analysis and smooth fitting tests were conducted to explore the independent relationship between plain water intake and periodontitis.ResultsA total of 5,882 participants were enrolled,62.02% have periodontitis. Periodontitis patients have lower plain water intake. The multivariable regression tests showed that the risk of periodontitis decreased with increased plain water intake quartiles (Q4 OR = 0.78; 95%CI 0.62–0.96) after fully adjustment. Subgroup analysis and interaction tests showed that gender, age, smoking, diabetes, hypertension or BMI does not significantly interact with the association. However, the relation was significant in males (Q4 OR = 0.64; 95%CI 0.47–0.86) but not in females (Q4 OR = 0.97;95% CI 0.71–1.31). In the smoothed curve fits stratified by gender, the curve for male participants displayed as a U-shape, with an optimal plain water intake at 1200 ml/day. For males drinking plain water less than 1200 ml/day, the risk of periodontitis decreased by 24% with each increase of 500 ml plain water intake (OR = 0.76, 95%CI 0.66–0.87, p < 0.001).ConclusionsTogether, the results showed that plain water intake is negatively associated with periodontitis risk in US middle aged and elderly population. Further studies are needed to investigate the mechanism unites this association. Attention should be given to adequate plain water intake when considering dietary suggestions to the population at high risk of developing periodontitis, especially for men.