ObjectiveTo explore the mechanism of herbal cake-separated moxibustion using the classical formula Xiaoyaosan in alleviating neuroimmune inflammatory responses in chronic fatigue syndrome （CFS） rats， based on the regulation of the toll-like receptor 4 （TLR4）/myeloid differentiation factor 88 （MyD88）/nuclear transcription factor-κB （NF-κB） signaling pathway. MethodsFifty SPF-grade SD rats aged 6-8 weeks were randomly divided into five groups： Normal group， model group， sham herbal cake moxibustion group， Chinese medicine intragastric administration group， and herbal cake-separated moxibustion group， with 10 rats in each group. Except for the normal group， all other groups underwent a 21-day modeling process， followed by behavioral testing. The herbal cake-separated moxibustion and sham herbal cake moxibustion groups received interventions at the Shenque （CV8）， Guanyuan （CV4）， Zusanli （ST36）， and Qimen （LR14） acupoints. The Chinese medicine intragastric administration group was treated with a Xiaoyaosan suspension via gavage. Behavioral tests were conducted after 10 days of continuous intervention. Serum levels of interleukin （IL）-1β， IL-6， and tumor necrosis factor-α （TNF-α）， as well as hippocampal levels of IL-1β， IL-6， TNF-α， and NF-κB， were detected by enzyme-linked immunosorbent assay （ELISA）. Morphological changes in the hippocampus were observed using hematoxylin-eosin （HE） staining. Real-time quantitative polymerase chain reaction （Real-time PCR） was used to detect mRNA expression levels of TLR4， MyD88， and NF-κB in the hippocampus. Western blot analysis was performed to detect the relative expression levels of TLR4， MyD88， NF-κB， and p65 proteins in the hippocampus. ResultsCompared with the normal group， the model group showed a significant decrease in upright times during the open field test （P<0.01）， as well as significant reductions in total movement distance， resting time， and center region duration （P<0.01）. In the tail suspension test， immobility time increased （P<0.01）， and struggle times decreased （P<0.01）. Serum and hippocampal levels of IL-1β， IL-6， and TNF-α， as well as hippocampal NF-κB levels and TLR4， MyD88， and NF-κB mRNA expression， were significantly elevated （P<0.01）. After treatment， compared with the model group， the total movement distance and upright times in the open field test were significantly increased in all treatment groups （P<0.01）， while resting time and center region duration were notably prolonged （P<0.05， P<0.01）. Immobility time in the tail suspension test was significantly shortened （P<0.01）， and struggle times significantly increased （P<0.05）. Serum and hippocampal levels of IL-1β， IL-6， TNF-α， hippocampal NF-κB levels， and TLR4 and NF-κB mRNA expression were significantly reduced （P<0.05， P<0.01）. Compared with the sham herbal cake moxibustion group， the herbal cake-separated moxibustion group showed a significant extension in center region duration during the open field test （P<0.05） and a significant increase in upright times （P<0.01）. In the tail suspension test， immobility time was reduced （P<0.01）， and struggle times increased （P<0.01）. Serum TNF-α levels in the Chinese medicine intragastric administration group were significantly reduced （P<0.01）， while serum IL-6 levels， as well as hippocampal levels of IL-1β， TNF-α， NF-κB， and TLR4， MyD88， and NF-κB mRNA expression， were significantly decreased in both the Chinese medicine intragastric administration group and the herbal cake-separated moxibustion group （P<0.05， P<0.01）. Compared with the Chinese medicine intragastric administration group， the herbal cake-separated moxibustion group exhibited significantly increased upright times in the open field test （P<0.01）. In the tail suspension test， immobility time was reduced （P<0.01）， and struggle times increased （P<0.01）. Serum IL-1β， hippocampal TNF-α levels， and TLR4， MyD88， and NF-κB mRNA expression were significantly decreased （P<0.05， P<0.01）. ConclusionHerbal cake-separated moxibustion effectively improves fatigue and memory function in CFS rats， regulates neuroimmune inflammatory responses， and its mechanism may be related to the modulation of the TLR4/MyD88/NF-κB signaling pathway.

Osteoporosis is a common senile bone metabolism disease， clinically characterized by decreased bone mass， destruction of bone microstructure， increased bone fragility， and easy fracture. It tends to occur in the elderly and postmenopausal women， seriously threatening the quality of life and physical and mental health of the elderly. At present， the treatment of osteoporosis is mainly based on oral western medicines， such as calcium， Vitamin D， and bisphosphonates. Still， there are drawbacks such as a long medication cycle and many adverse reactions. In recent years， due to the advantages of multi-component， multi-pathway， and multi-target， some traditional Chinese medicines and effective ingredients can regulate the osteogenic and osteoclastic differentiation process in both directions and are widely used in the prevention and treatment of osteoporosis. Hippophae rhamnoides is a commonly used herbal medicine， and its fruits are rich in flavonoids， polyphenols， fatty acids， vitamins， and trace elements， which have been proven to have a good anti-osteoporosis effect. Isorhamnetin is the main effective ingredient of Hippophae rhamnoides fruits， which has many pharmacological effects such as anti-inflammation， anti-oxidative stress， anti-aging， and anti-tumor. Studies have shown that isorhamnetin can participate in the regulation of bone metabolism and has a good anti-osteoporosis effect. However， the pharmacological effects and related mechanisms of isorhamnetin against osteoporosis have not been systematically summarized. Therefore， this paper reviewed the pharmacological effects and related mechanisms of isorhamnetin against osteoporosis by referring to relevant literature to provide more basis for the development and application of isorhamnetin.

ObjectiveTo explore the mechanism of moxibustion with the classical prescription Xiaoyaosan as the herbal cake in improving cognitive function in the rat model of chronic fatigue syndrome （CFS） by regulating autophagy via phosphatidylinosiol 3-kinase （PI3K）/autophagy key molecule yeast Atg6 homologue 1 （Beclin1） signaling pathway. MethodsFifty SPF-grade SD rats aged 6-8 weeks were randomly grouped as follows： control， model， sham cake-separated moxibustion， intragastric administration with Chinese herbs， and herbal cake-separated moxibustion， each with 10 rats. The other groups except the control group were subjected to modeling by exhaustive swimming and chronic restraint stress for 21 days， and the behavioral test was performed after modeling. Herbal cake-separated moxibustion and sham cake-separated moxibustion were carried out at Shenque （CV8）， Guanyuan （CV4）， Zusanli （ST36）， and Qimen （LR14）. The rats in the intragastric administration with Chinese herbs group were treated with Xiaoyaosan suspension by gavage. After continuous intervention for 10 days， rat behaviors were observed and the levels of interleukin （IL）-4， IL-10， blood urine nitrogen （BUN）， and malondiadehyde （MDA） in the serum and hippocampal tissue of rats in each group were determined by enzyme-linked immunosorbent assay. The morphological changes of the hippocampal tissue were observed by hematoxylin-eosin staining. The relative mRNA and protein levels of PI3K and Beclin1 in the hippocampal tissue were determined by Real-time quantitative polymerase chain reaction （Real-time PCR） and Western blot， respectively. ResultsCompared with the normal group， the model group showed reduced crossings， shortened residence time in the target quadrant， and prolonged average escape latency on days 1， 2， 3， and 4 （P<0.01） in the Morris water maze test. In the new object recognition test， the model group showed decreased recognition index of exploration time and recognition index of exploration times （P<0.01）， lowered levels of IL-4 and IL-10 and elevated levels of BUN and MDA in the serum and hippocampus （P<0.01）， and down-regulated mRNA and protein levels of PI3K and Beclin1 （P<0.01）. After treatment， compared with the model group， each treatment group showed increased crossings， prolonged residence time in the target quadrant， and shortened average escape latency on days 1， 2， 3， and 4 （P<0.05， P<0.01）. In addition， the treatment elevated the levels of IL-4 and IL-10 and lowered the levels of BUN and MDA in the serum and hippocampus （P<0.05， P<0.01）， and up-regulated the mRNA and protein levels of PI3K and Beclin1 （P<0.05， P<0.01）. Compared with the sham cake-separated moxibustion group， the herbal cake-separated moxibustion group and the intragastric administration with Chinese herbs group showed increased crossings， prolonged residence time in the target quadrant （P<0.05）， elevated level of IL-4， lowered level of MDA， and up-regulated relative mRNA and protein levels of PI3K and Beclin1 in the hippocampus （P<0.05， P<0.01）. The serum levels of MDA and BUN in the intragastric administration with Chinese herbs group were significantly decreased. The average escape latency of the herbal cake-separated moxibustion group was significantly shortened on days 2 and 3 （P<0.05， P<0.01）. In addition， this group showed elevated serum level of IL-4， lowered serum level of MDA， and declined BUN level in the hippocampus （P<0.05， P<0.01）. Compared with the intragastric administration with Chinese herbs group， the herbal cake-separated moxibustion group presented risen serum level of IL-4 and up-regulated mRNA level of Beclin1 （P<0.05） and relative protein levels of PI3K and Beclin1 （P<0.05， P<0.01）. ConclusionHerbal cake-separated moxibustion can effectively alleviate fatigue and improve the memory， reduce inflammatory response and oxidative stress， and decrease autophagy of hippocampal neurons in CFS rats by regulating the PI3K/Beclin1 signaling pathway.

ObjectiveTo explore the mechanism of moxibustion with the classical prescription Xiaoyaosan as the herbal cake in improving cognitive function in the rat model of chronic fatigue syndrome （CFS） by regulating autophagy via phosphatidylinosiol 3-kinase （PI3K）/autophagy key molecule yeast Atg6 homologue 1 （Beclin1） signaling pathway. MethodsFifty SPF-grade SD rats aged 6-8 weeks were randomly grouped as follows： control， model， sham cake-separated moxibustion， intragastric administration with Chinese herbs， and herbal cake-separated moxibustion， each with 10 rats. The other groups except the control group were subjected to modeling by exhaustive swimming and chronic restraint stress for 21 days， and the behavioral test was performed after modeling. Herbal cake-separated moxibustion and sham cake-separated moxibustion were carried out at Shenque （CV8）， Guanyuan （CV4）， Zusanli （ST36）， and Qimen （LR14）. The rats in the intragastric administration with Chinese herbs group were treated with Xiaoyaosan suspension by gavage. After continuous intervention for 10 days， rat behaviors were observed and the levels of interleukin （IL）-4， IL-10， blood urine nitrogen （BUN）， and malondiadehyde （MDA） in the serum and hippocampal tissue of rats in each group were determined by enzyme-linked immunosorbent assay. The morphological changes of the hippocampal tissue were observed by hematoxylin-eosin staining. The relative mRNA and protein levels of PI3K and Beclin1 in the hippocampal tissue were determined by Real-time quantitative polymerase chain reaction （Real-time PCR） and Western blot， respectively. ResultsCompared with the normal group， the model group showed reduced crossings， shortened residence time in the target quadrant， and prolonged average escape latency on days 1， 2， 3， and 4 （P<0.01） in the Morris water maze test. In the new object recognition test， the model group showed decreased recognition index of exploration time and recognition index of exploration times （P<0.01）， lowered levels of IL-4 and IL-10 and elevated levels of BUN and MDA in the serum and hippocampus （P<0.01）， and down-regulated mRNA and protein levels of PI3K and Beclin1 （P<0.01）. After treatment， compared with the model group， each treatment group showed increased crossings， prolonged residence time in the target quadrant， and shortened average escape latency on days 1， 2， 3， and 4 （P<0.05， P<0.01）. In addition， the treatment elevated the levels of IL-4 and IL-10 and lowered the levels of BUN and MDA in the serum and hippocampus （P<0.05， P<0.01）， and up-regulated the mRNA and protein levels of PI3K and Beclin1 （P<0.05， P<0.01）. Compared with the sham cake-separated moxibustion group， the herbal cake-separated moxibustion group and the intragastric administration with Chinese herbs group showed increased crossings， prolonged residence time in the target quadrant （P<0.05）， elevated level of IL-4， lowered level of MDA， and up-regulated relative mRNA and protein levels of PI3K and Beclin1 in the hippocampus （P<0.05， P<0.01）. The serum levels of MDA and BUN in the intragastric administration with Chinese herbs group were significantly decreased. The average escape latency of the herbal cake-separated moxibustion group was significantly shortened on days 2 and 3 （P<0.05， P<0.01）. In addition， this group showed elevated serum level of IL-4， lowered serum level of MDA， and declined BUN level in the hippocampus （P<0.05， P<0.01）. Compared with the intragastric administration with Chinese herbs group， the herbal cake-separated moxibustion group presented risen serum level of IL-4 and up-regulated mRNA level of Beclin1 （P<0.05） and relative protein levels of PI3K and Beclin1 （P<0.05， P<0.01）. ConclusionHerbal cake-separated moxibustion can effectively alleviate fatigue and improve the memory， reduce inflammatory response and oxidative stress， and decrease autophagy of hippocampal neurons in CFS rats by regulating the PI3K/Beclin1 signaling pathway.

Objective:To determine the optimal cut-off value of serum cotinine for distinguishing smoking status among Chinese adults based on a large-scale national sample.Methods:A cross-sectional study was conducted among 8 987 Chinese adults aged 20-79 years from 152 administrative counties across 31 provinces during 2017-2018. Sociodemographic characteristics, lifestyle, smoking status, and health status were collected via questionnaires and physical examinations. Blood samples were analyzed for serum cotinine levels using liquid chromatography-mass spectrometry and for blood creatinine levels using the picric acid method. Receiver operating characteristic (ROC) curve analysis was performed with serum cotinine concentration as the test variable and self-reported smoking status as the state variable. The optimal cut-off value was determined based on the maximum Youden′s index, and the bootstrap method was used for repeated sampling (2 000 times) to evaluate the confidence interval of the cut-off value. The net reclassification index (NRI) was used to evaluate the discrimination ability of the cut-off value of this study, the cut-off value of the American population 1 (total population: 3.3 μg/L, men: 4.1 μg/L, women: 3.0 μg/L) and the cut-off value of the American population 2 (the recommended value of the United States Centers for Disease Control and Prevention for the total population: 10.0 μg/L) against the smoking status of the Chinese population. Statistical analyses were conducted using IBM SPSS 27 and Python 3.11, with a significance level of α=0.05.Results:The age of the research subjects was (49.2±15.2) years. Among them, males accounted for 49.8% (4 477); smokers accounted for 28.8% (2 586); the detection rate of serum cotinine was 94.6% (8 501), and the M ( Q1, Q3) concentration of serum cotinine was 0.9 (0.3, 85.4) μg/L. The ROC curve analysis results showed that the cut-off value (95% CI) of serum cotinine in the total population was 8.8 (6.7-11.7) μg/L, with the specificity (95% CI) about 93.6%(92.7%-94.3%), the sensitivity (95% CI) about 91.0%(89.7%-92.3%) and the area under the curve (AUC) (95% CI) about 0.93 (0.92-0.94). The cut-off value (95% CI) of cotinine for males was 17.1 (8.8-21.8) μg/L, with the specificity (95% CI) about 90.7%(87.9%-92.0%), the sensitivity (95% CI) about 89.4%(88.4%-92.2%) and the AUC (95% CI) about 0.92 (0.91-0.93). The cut-off value (95% CI) of cotinine for females was 7.4 (3.3-15.0) μg/L, with the specificity (95% CI) about 95.6%(92.7%-96.8%), the sensitivity (95% CI) about 87.6%(81.6%-92.8%) and the AUC (95% CI) about 0.92 (0.87-0.95). The NRI analysis results showed that compared with the cut-off value of the American population 2, the NRI of this study′s cut-off values in the total population, males and females were 0.020 ( P=0.015), 0.033 ( P=0.015) and 0.011 ( P=0.380), respectively, indicating that this study′s cutoff value could have better classification performance in the total population and males. Compared with the cut-off value of the American population 2, the NRI of the total population in this study was 0.001 ( P=0.285). Conclusion:The serum cotinine cut-off value based on the analysis of large sample data in China is more suitable for distinguishing the smoking status of Chinese adults.

Objective:To investigate the association between blood selenium levels and sex hormones in Chinese men aged 18-79 years.Methods:Data were derived from the China National Human Biomonitoring survey conducted in 2017-2018, with a final sample size of 5 414 men. General demographic characteristics, behavioral habits, and dietary frequency were collected through questionnaires and physical examinations. Fasting blood samples were collected to measure blood lead, serum testosterone, and estradiol levels. Complex sampling linear regression models were used to analyze the associations between blood selenium levels and testosterone, estradiol, and the testosterone/estradiol ratio, adjusting for confounding factors including age, education level, marital status, smoking status, alcohol consumption, seafood intake, soy product intake, protein supplement intake, BMI, and diabetes status.Results:The mean age of the 5 414 participants was (46.85±27.91) years; 4 774 (91.65%) were of Han ethnicity and 4 505 (86.68%) were married. The median ( Q1, Q3) blood selenium concentration in men was 97.80 (80.64, 116.99) μg/L. After adjusting for confounding factors, the complex sampling linear regression model revealed negative associations between blood selenium levels and both testosterone levels and the testosterone/estradiol ratio, with a significant linear trend ( Ptrend<0.05). Compared with the Q1 group, the β (95% CI) values for testosterone in the Q2, Q3, and Q4 groups were -0.02 (-0.06 to 0.02), -0.03 (-0.08 to 0.01), and -0.06 (-0.09 to -0.02), respectively. Similarly, the β (95% CI) values for the testosterone/estradiol ratio in the Q2, Q3, and Q4 groups were -0.01 (-0.03 to 0.02), -0.01 (-0.04 to 0.04), and -0.03 (-0.06 to -0.01), respectively. Subgroup analysis indicated stronger associations between blood selenium levels and testosterone/estradiol levels in non-smoking and obese men (BMI≥28 kg/m2). Conclusion:Blood selenium levels are negatively associated with testosterone levels and the testosterone/estradiol ratio in Chinese adult males.

Objective:To explore the association of blood and urinary cadmium levels with lipid profile levels and dyslipidemia in Chinese adults aged 18 to 79 years.Methods:Based on the China National Human Biomonitoring (CNHBM) program, a cross-sectional survey was conducted from 2017 to 2018 using a multi-stage stratified random sampling method, including a total of 10 713 adults aged 18 to 79 years. Data was obtained through questionnaires, physical examinations, biological sample collection, and laboratory testing. Multiple linear mixed effect model (MLMM) and generalized linear mixed effect model (GLMM) were used to analyze the association of blood and creatinine-corrected urinary cadmium levels with lipid profile levels as well as dyslipidemia among adults.Results:The age of 10 713 participants was (47.23±0.24) years, with 5 372 males accounting for 61.3% of the national population. The weighted mean±standard error (SE) of total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) was (5.21±0.03), (1.86±0.03), (2.96±0.03), and (1.43±0.01) mmol/L, respectively. The prevalence rate of hypercholesterolemia, hypertriglyceridemia, mixed hyperlipidemia, low HDL-C, and high LDL-C was 16.0%, 21.6%, 6.6%, 13.5%, and 10.0%, respectively. MLMM showed that, after adjusting for relevant confounders, log-transformed blood cadmium levels were positively associated with increased levels of TC, TG and LDL-C ( P<0.05). When blood cadmium levels were categorized into quartiles, compared to the lowest exposure group ( Q1), participants in the highest blood cadmium exposure group ( Q4) had increases of 0.19 (95% CI: 0.06, 0.32) mmol/L in TC and 0.25 (95% CI: 0.08, 0.43) mmol/L in TG. GLMM indicated that, after adjusting for confounders, higher blood cadmium exposure levels were associated with increased risks of hypercholesterolemia, hypertriglyceridemia, mixed hyperlipidemia, and high LDL-C ( P<0.05). Further analysis by quartiles showed that, compared to the blood cadmium Q1 exposure group, the OR value (95% CI) for the Q4 group was 1.53 (1.12, 2.08) for hypercholesterolemia, 1.54 (1.09, 2.17) for hypertriglyceridemia, 2.24 (1.47, 3.40) for mixed hyperlipidemia, and 1.49 (1.07, 2.09) for high LDL-C. Conclusion:The cadmium internal exposure levels are associated with blood lipid profile levels as well as the incidence of dyslipidemia in Chinese adults aged 18 to 79.

Objective:To investigate the association between blood selenium levels and sex hormones in Chinese men aged 18-79 years.Methods:Data were derived from the China National Human Biomonitoring survey conducted in 2017-2018, with a final sample size of 5 414 men. General demographic characteristics, behavioral habits, and dietary frequency were collected through questionnaires and physical examinations. Fasting blood samples were collected to measure blood lead, serum testosterone, and estradiol levels. Complex sampling linear regression models were used to analyze the associations between blood selenium levels and testosterone, estradiol, and the testosterone/estradiol ratio, adjusting for confounding factors including age, education level, marital status, smoking status, alcohol consumption, seafood intake, soy product intake, protein supplement intake, BMI, and diabetes status.Results:The mean age of the 5 414 participants was (46.85±27.91) years; 4 774 (91.65%) were of Han ethnicity and 4 505 (86.68%) were married. The median ( Q1, Q3) blood selenium concentration in men was 97.80 (80.64, 116.99) μg/L. After adjusting for confounding factors, the complex sampling linear regression model revealed negative associations between blood selenium levels and both testosterone levels and the testosterone/estradiol ratio, with a significant linear trend ( Ptrend<0.05). Compared with the Q1 group, the β (95% CI) values for testosterone in the Q2, Q3, and Q4 groups were -0.02 (-0.06 to 0.02), -0.03 (-0.08 to 0.01), and -0.06 (-0.09 to -0.02), respectively. Similarly, the β (95% CI) values for the testosterone/estradiol ratio in the Q2, Q3, and Q4 groups were -0.01 (-0.03 to 0.02), -0.01 (-0.04 to 0.04), and -0.03 (-0.06 to -0.01), respectively. Subgroup analysis indicated stronger associations between blood selenium levels and testosterone/estradiol levels in non-smoking and obese men (BMI≥28 kg/m2). Conclusion:Blood selenium levels are negatively associated with testosterone levels and the testosterone/estradiol ratio in Chinese adult males.

Objective:To explore the association of blood and urinary cadmium levels with lipid profile levels and dyslipidemia in Chinese adults aged 18 to 79 years.Methods:Based on the China National Human Biomonitoring (CNHBM) program, a cross-sectional survey was conducted from 2017 to 2018 using a multi-stage stratified random sampling method, including a total of 10 713 adults aged 18 to 79 years. Data was obtained through questionnaires, physical examinations, biological sample collection, and laboratory testing. Multiple linear mixed effect model (MLMM) and generalized linear mixed effect model (GLMM) were used to analyze the association of blood and creatinine-corrected urinary cadmium levels with lipid profile levels as well as dyslipidemia among adults.Results:The age of 10 713 participants was (47.23±0.24) years, with 5 372 males accounting for 61.3% of the national population. The weighted mean±standard error (SE) of total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) was (5.21±0.03), (1.86±0.03), (2.96±0.03), and (1.43±0.01) mmol/L, respectively. The prevalence rate of hypercholesterolemia, hypertriglyceridemia, mixed hyperlipidemia, low HDL-C, and high LDL-C was 16.0%, 21.6%, 6.6%, 13.5%, and 10.0%, respectively. MLMM showed that, after adjusting for relevant confounders, log-transformed blood cadmium levels were positively associated with increased levels of TC, TG and LDL-C ( P<0.05). When blood cadmium levels were categorized into quartiles, compared to the lowest exposure group ( Q1), participants in the highest blood cadmium exposure group ( Q4) had increases of 0.19 (95% CI: 0.06, 0.32) mmol/L in TC and 0.25 (95% CI: 0.08, 0.43) mmol/L in TG. GLMM indicated that, after adjusting for confounders, higher blood cadmium exposure levels were associated with increased risks of hypercholesterolemia, hypertriglyceridemia, mixed hyperlipidemia, and high LDL-C ( P<0.05). Further analysis by quartiles showed that, compared to the blood cadmium Q1 exposure group, the OR value (95% CI) for the Q4 group was 1.53 (1.12, 2.08) for hypercholesterolemia, 1.54 (1.09, 2.17) for hypertriglyceridemia, 2.24 (1.47, 3.40) for mixed hyperlipidemia, and 1.49 (1.07, 2.09) for high LDL-C. Conclusion:The cadmium internal exposure levels are associated with blood lipid profile levels as well as the incidence of dyslipidemia in Chinese adults aged 18 to 79.

Objective:To determine the optimal cut-off value of serum cotinine for distinguishing smoking status among Chinese adults based on a large-scale national sample.Methods:A cross-sectional study was conducted among 8 987 Chinese adults aged 20-79 years from 152 administrative counties across 31 provinces during 2017-2018. Sociodemographic characteristics, lifestyle, smoking status, and health status were collected via questionnaires and physical examinations. Blood samples were analyzed for serum cotinine levels using liquid chromatography-mass spectrometry and for blood creatinine levels using the picric acid method. Receiver operating characteristic (ROC) curve analysis was performed with serum cotinine concentration as the test variable and self-reported smoking status as the state variable. The optimal cut-off value was determined based on the maximum Youden′s index, and the bootstrap method was used for repeated sampling (2 000 times) to evaluate the confidence interval of the cut-off value. The net reclassification index (NRI) was used to evaluate the discrimination ability of the cut-off value of this study, the cut-off value of the American population 1 (total population: 3.3 μg/L, men: 4.1 μg/L, women: 3.0 μg/L) and the cut-off value of the American population 2 (the recommended value of the United States Centers for Disease Control and Prevention for the total population: 10.0 μg/L) against the smoking status of the Chinese population. Statistical analyses were conducted using IBM SPSS 27 and Python 3.11, with a significance level of α=0.05.Results:The age of the research subjects was (49.2±15.2) years. Among them, males accounted for 49.8% (4 477); smokers accounted for 28.8% (2 586); the detection rate of serum cotinine was 94.6% (8 501), and the M ( Q1, Q3) concentration of serum cotinine was 0.9 (0.3, 85.4) μg/L. The ROC curve analysis results showed that the cut-off value (95% CI) of serum cotinine in the total population was 8.8 (6.7-11.7) μg/L, with the specificity (95% CI) about 93.6%(92.7%-94.3%), the sensitivity (95% CI) about 91.0%(89.7%-92.3%) and the area under the curve (AUC) (95% CI) about 0.93 (0.92-0.94). The cut-off value (95% CI) of cotinine for males was 17.1 (8.8-21.8) μg/L, with the specificity (95% CI) about 90.7%(87.9%-92.0%), the sensitivity (95% CI) about 89.4%(88.4%-92.2%) and the AUC (95% CI) about 0.92 (0.91-0.93). The cut-off value (95% CI) of cotinine for females was 7.4 (3.3-15.0) μg/L, with the specificity (95% CI) about 95.6%(92.7%-96.8%), the sensitivity (95% CI) about 87.6%(81.6%-92.8%) and the AUC (95% CI) about 0.92 (0.87-0.95). The NRI analysis results showed that compared with the cut-off value of the American population 2, the NRI of this study′s cut-off values in the total population, males and females were 0.020 ( P=0.015), 0.033 ( P=0.015) and 0.011 ( P=0.380), respectively, indicating that this study′s cutoff value could have better classification performance in the total population and males. Compared with the cut-off value of the American population 2, the NRI of the total population in this study was 0.001 ( P=0.285). Conclusion:The serum cotinine cut-off value based on the analysis of large sample data in China is more suitable for distinguishing the smoking status of Chinese adults.