DNA Polymerase-Endonuclease Efficiently Synthesizes DNA to Prepare DNA Materials and Develop Novel Signal Amplification System.

DNA biosynthesis, a focus of fundamental and applied research, typically involves DNA polymerases by using templates, primers, and dNTPs. Some polymerases can polymerize dNTPs for DNA de novo synthesis, although this is generally to occur randomly. This novel synthesis method has garnered our attention and practical use. Herein, we observed that the addition of endonuclease significantly enhances the efficiency of the de novo synthesis reaction catalyzed by the DNA polymerase. We further investigated the reaction conditions that influence this efficiency. Building on the optimal reaction conditions, we developed a rapid and efficient strategy for preparing DNA hydrogel. Further, coupled with the CRISPR-Cas system, we developed a nucleic acid signal amplification system characterized by versatility, sensitivity, specificity, and no risk of aerosol contamination. We successfully detected viral nucleic acids in clinical samples. In summary, our study demonstrates the significant potential of DNA polymerase- and endonuclease-catalyzed DNA de novo synthesis in diverse applications.

Attitudes towards snakebite health education and associated factors among residents in China: A national cross-sectional study.

Background: This study aimed to investigate attitudes towards health education on snakebites and to identify the influencing factors among Chinese residents. Additionally, we proposed effective health education strategies for snakebite management. Methods: Between May 2022 and February 2023, we conducted a nationwide cross-sectional questionnaire survey using a multistage sampling method with supplementary snowball sampling. We used descriptive analysis, χ2 tests, and univariable and multivariable binary logistic regression models to analyse the data. Results: We included 56 669 respondents in the analysis. The average score for snakebite knowledge was 12.13 ± 5.26 points, with a maximum score of 28. Among the respondents, 72.66 and 63.03% of the residents believed that it was necessary to disseminate knowledge about snakebites and expressed a willingness to receive snakebite training, respectively. Respondents from the northeast region, respondents with a higher education level, and respondents with higher scores for snakebite knowledge, health knowledge, health skills, and social-psychological adjustment skills exhibited more positive attitudes towards snakebite knowledge dissemination and training. Conversely, respondents from eastern or southern China, respondents older than 60, and respondents who lived in rudimentary housing conditions showed a lower perception of the need for snakebite knowledge dissemination and were less willing to participate in snakebite knowledge and skill training. Conclusions: Generally, Chinese residents have positive attitudes towards snakebite knowledge dissemination and training. However, the public lacks sufficient knowledge about snakebites. Therefore, we should pay close attention to areas south of the Yangtze River to strengthen snakebite health education using engaging formats that align with residents' interests, such as short videos or television programmes, in an attempt to and ultimately improve health literacy and prevention awareness.

Association between nighttime sleep duration, midday napping, and sleep quality during early pregnancy and risk of gestational diabetes mellitus: A prospective cohort study in China.

AIM: To evaluate the prospective associations of nighttime sleep duration, midday napping, and sleep quality during early pregnancy with gestational diabetes mellitus (GDM) risk among Chinese pregnant women. METHODS: Sleep-related information was assessed by the Pittsburgh Sleep Quality Index in baseline surveys during the 6-15 (mean 10.3) gestational weeks. GDM was diagnosed during 24-28 gestational weeks according to the Chinese Guidelines on Diagnosis and Management of Hyperglycemia in Pregnancy (2022). Multivariable logistic regression models with adjustments for socio-demographic and lifestyle factors were used to estimate odds ratios (ORs) and 95 % confidence intervals (CIs) for the associations of sleep traits with GDM risk. RESULTS: We identified 503 incident GDM cases among 6993 participants. Compared with women who slept for 7-9 hours/night in early pregnancy, those who slept <7 hours/night showed a higher risk of GDM (OR, 1.75; 95 % CI: 1.20-2.54), whereas those who slept >9 hours/night showed no significant association for GDM risk (OR, 1.01; 95 % CI: 0.78-1.30). Compared with women with absolutely no napping, those with ≤60 and > 60 min/day midday napping showed no significant association for GDM risk (OR, 0.82; 95 % CI: 0.64-1.05 for ≤60 min/day midday napping; OR, 0.87; 95 % CI: 0.66-1.15 for >60 min/day midday napping). Poor sleep quality was not associated with GDM risk compared with good quality (OR, 0.90; 95 % CI: 0.72-1.12). CONCLUSION: A short nighttime sleep duration during early pregnancy was associated with a higher risk of GDM, which was independent of midday napping, sleep quality and lifestyle factors.

Knowledge and practices related to snakebite prevention, China: a cross-sectional study.

Objective: To assess knowledge and practices related to snakebite prevention among Chinese residents. Methods: By using a multistage random sampling approach augmented by snowball sampling, we surveyed residents from 10 provinces, one municipality and one autonomous region south of the Yangtze River Basin between May 2022 and February 2023. We supplemented the data with a national online survey. We used a χ2-test to identify differences in knowledge and behaviour across various demographic characteristics. We conducted multifactor logistic regression analyses to evaluate factors potentially influencing snakebite knowledge and practices. Findings: We obtained 55 775 valid survey responses, 16 200 respondents from the face-to-face survey and 39 575 respondents from the online survey. Only 25.7% (14 325) respondents demonstrated adequate knowledge about snakebites whereas 25.6% (14 295) respondents knew basic first-aid practices or preventive behaviours. Age, marital status, educational attainment, occupation, type of residence and frequency of exposure to nature are significant independent variables affecting snakebite knowledge (P-values: < 0.05). On the other hand, gender, age, marital status, educational attainment, occupation and type of residence were significant independent variables affecting the behaviour of snakebite prevention and first aid (P-values: < 0.05). Conclusion: There is a notable shortfall in knowledge, first aid and preventive behaviours among Chinese residents regarding snakebites. Misguided first aid practices can severely compromise the effectiveness of evidence-based therapeutic interventions. Consequently, improving health education concerning snakes and snakebites in this population is needed.

The protective effects of ruscogenin against lipopolysaccharide-induced myocardial injury in septic mice.

ABSTRACT: Sepsis-induced myocardial dysfunction (SIMD) commonly occurs in individuals with sepsis and is a severe complication with high morbidity and mortality rates. The current study aimed to investigate the effects and potential mechanisms of the natural steroidal sapogenin ruscogenin (RUS) against lipopolysaccharide (LPS)-induced myocardial injury in septic mice. We found that RUS effectively alleviated myocardial pathological damage, normalized cardiac function, and increased survival in septic mice. RNA sequencing (RNA-seq) demonstrated that RUS administration significantly inhibited the activation of the NOD-like receptor signaling pathway in the myocardial tissues of septic mice. Subsequent experiments further confirmed that RUS suppressed myocardial inflammation and pyroptosis during sepsis. Additionally, cultured HL-1 cardiomyocytes were challenged with LPS, and we observed that RUS could protect these cells against LPS-induced cytotoxicity by suppressing inflammation and pyroptosis. Notably, both the in vivo and in vitro findings indicated that RUS inhibited NLRP3 upregulation in cardiomyocytes stimulated with LPS. As expected, knockdown of NLRP3 blocked the LPS-induced activation of inflammation and pyroptosis in HL-1 cells. Furthermore, the cardioprotective effects of RUS on HL-1 cells under LPS stimulation were abolished by the novel NLRP3 agonist BMS-986299. Taken together, our results suggest that RUS can alleviate myocardial injury during sepsis, at least in part by suppressing NLRP3-mediated inflammation and pyroptosis, highlighting the potential of this molecule as a promising candidate for SIMD therapy.

A national survey on current state and development needs of clinical and academic emergency medicine in China.

BACKGROUND: To characterize the current state of emergency medicine (EM) and the requirements for advancing EM clinical practice, education and research in China. METHODS: An anonymous electronic survey was conducted by Chinese Society of Emergency Medicine during September to October 2021. The survey contained 30 questions divided into 2 sections: the current state of EM development and the requirements for EM growth. RESULTS: 722 hospitals were included, of 487 were Level III and 235 were Level II hospitals. We found that after 40 years of development, EM had established a mature disciplinary system and refined sub-specialties including critical care, cardiopulmonary resuscitation, toxicology, disaster and emergency rescue. In Level III hospitals, 70.8% of EDs were standardized training centers for EM residents, but master's degree program, Doctor Degree program and post-doctoral degree program was approved in only 37.8%, 8.4% and 2.9% of EDs respectively and postgraduate curriculum was available in 1/4 of EDs. Only 8% have national or provincial key laboratories. In addition to advance clinical practice, there was also a high demand to improve teaching and research capacities, mainly focusing on literature review, research design and delivery, paper writing, residency training. CONCLUSIONS: EM has built a mature discipline system and refined sub-specialties in China. Teaching and research developed parallel with clinical practice. However, there was still a lack of EM master's and doctoral programs and research capacities need to be improved. More outstanding clinical and academic training should be provided to promote the rapid growth of EM in China.

Capsaicin Attenuates LPS-Induced Acute Lung Injury by Inhibiting Inflammation and Autophagy Through Regulation of the TRPV1/AKT Pathway.

Purpose: Acute lung injury (ALI) is a severe pulmonary disease characterized by damage to the alveoli and pulmonary blood vessels, leading to severe impairment of lung function. Studies on the effect of capsaicin (8-methyl-N-geranyl-6-nonamide, CAP) on lipopolysaccharide (LPS)-induced ALI in bronchial epithelial cells transformed with Ad12-SV40 2B (BEAS-2B) are still limited. This study aimed to investigate the effect and specific mechanism by which CAP improves LPS-induced ALI. Methods: The present study investigated the effect of CAP and the potential underlying mechanisms in LPS-induced ALI in vitro and vivo via RNA sequencing, Western blotting (WB), quantitative real-time reverse transcription PCR (qRT‒PCR), enzyme-linked immunosorbent assay (ELISA), and transmission electron microscopy (TEM). The TRPV1 inhibitor AMG9810 and the AKT agonist SC79 were used to confirm the protective effect of the TRPV1/AKT axis against ALI. The autophagy agonist rapamycin (Rapa) and the autophagy inhibitors 3-methyladenine (3-MA) and bafilomycin A1 (Baf-A1) were used to clarify the characteristics of LPS-induced autophagy. Results: Our findings demonstrated that CAP effectively suppressed inflammation and autophagy in LPS-induced ALI, both in vivo and in vitro. This mechanism involves regulation by the TRPV1/AKT signaling pathway. By activating TRPV1, CAP reduces the expression of P-AKT, thereby exerting its anti-inflammatory and inhibitory effects on pro-death autophagy. Furthermore, prior administration of CAP provided substantial protection to mice against ALI induced by LPS, reduced the lung wet/dry ratio, decreased proinflammatory cytokine expression, and downregulated LC3 expression. Conclusion: Taken together, our results indicate that CAP protects against LPS-induced ALI by inhibiting inflammatory responses and autophagic death through the TRPV1/AKT signaling pathway, presenting a novel strategy for ALI therapy.

Fe-Capsaicin Nanozymes Attenuate Sepsis-Induced Acute Lung Injury via NF-κB Signaling.

Background: In sepsis, the lungs are one of the most severely affected organs, usually resulting in acute lung injury (ALI). Capsaicin (CAP) is a natural compound found in chili peppers that has pain-relieving and anti-inflammatory properties. Here, we report that nanoparticles containing capsaicin and iron (Fe-CAP NPs) exhibited anti-inflammatory effects in the treatment of ALI. Methods: The morphological characteristics of nanozymes were detected. RAW 264.7 cells were divided into four groups: control, lipopolysaccharide (LPS), CAP+LPS and Fe-CAP+LPS groups. The expression of inducible nitric oxide synthase (iNOS), transforming growth factor-ß (TGF-ß), and tumor necrosis factor-α (TNF-α) was assessed by immunofluorescence, Western blot, and enzyme-linked immunosorbent assay (ELISA). Nuclear factor kappa-B (NF-κB) expression was determined by Western blot. C57 mice were divided into control, LPS, CAP+LPS and Fe-CAP+LPS groups. Interleukin-6 (IL-6) and iNOS expression in the lung was detected by Western Blot. IL-6 and TNF-α expression in serum was detected by ELISA. Extravasated Evans blue, histopathological evaluation and wet-to-dry (W/D) weight ratio were used to assess pulmonary capillary permeability. The blood and major organs (heart, liver, spleen, lung and kidney) of mice were tested for the toxicity of Fe-CAP NPs. Results: In the LPS group, TNF-α, iNOS, p-NF-κB and p-IKBα expression increased. However, their expression was significantly decreased in the Fe-CAP+LPS group. TGF-ß expression showed the opposite trend. In vivo, IL-6 and iNOS expression was notably increased in the lungs of LPS group of mice but decreased with Fe-CAP pretreatment. Fe-CAP significantly ameliorated lung EB leakage, improved the histopathology of lung tissue and reduced the W/D weight ratio. The nanoparticles showed non-cytotoxicity, when studying these biological activities. Conclusion: Fe-CAP NPs could alleviated inflammation by inhibiting the expression of pro-inflammatory factors in macrophages, increasing the expression of anti-inflammatory factors, and alleviating lung tissue damage.

Capsaicin Enhanced the Efficacy of Photodynamic Therapy Against Osteosarcoma via a Pro-Death Strategy by Inducing Ferroptosis and Alleviating Hypoxia.

Ferroptosis, a novel form of nonapoptotic cell death, can effectively enhance photodynamic therapy (PDT) performance by disrupting intracellular redox homeostasis and promoting apoptosis. However, the extremely hypoxic tumor microenvironment (TME) together with highly expressed hypoxia-inducible factor-1α (HIF-1α) presents a considerable challenge for clinical PDT against osteosarcoma (OS). Hence, an innovative nanoplatform that enhances antitumor PDT by inducing ferroptosis and alleviating hypoxia is fabricated. Capsaicin (CAP) is widely reported to specifically activate transient receptor potential vanilloid 1 (TRPV1) channel, trigger an increase in intracellular Ca2+ concentration, which is closely linked with ferroptosis, and participate in decreased oxygen consumption by inhibiting HIF-1α in tumor cells, potentiating PDT antitumor efficiency. Thus, CAP and the photosensitizer IR780 are coencapsulated into highly biocompatible human serum albumin (HSA) to construct a nanoplatform (CI@HSA NPs) for synergistic tumor treatment under near-infrared (NIR) irradiation. Furthermore, the potential underlying signaling pathways of the combination therapy are investigated. CI@HSA NPs achieve real-time dynamic distribution monitoring and exhibit excellent antitumor efficacy with superior biosafety in vivo. Overall, this work highlights a promising NIR imaging-guided "pro-death" strategy to overcome the limitations of PDT for OS by promoting ferroptosis and alleviating hypoxia, providing inspiration and support for future innovative tumor therapy approaches.

Maternal overweight and obesity modify the association of serum fibroblast growth factor 21 levels with gestational diabetes mellitus: A nested case-control study.

AIMS: To examine the prospective association between fibroblast growth factor 21 (FGF21) and risk of gestational diabetes mellitus (GDM) and the modifying effect of overweight/obesity for this association. METHODS: Serum FGF21 levels were measured at 6-15 weeks of gestation among 332 GDM cases and 664 matched controls. Conditional logistic regression was used to evaluate its association with GDM risk. Interaction analyses on multiplicative and additive scales were conducted to investigate the modifying effect of overweight/obesity. RESULTS: Elevated FGF21 levels were associated with a higher risk of GDM in multivariable models, but the positive association was attenuated after further adjustment for pre-pregnancy body mass index (BMI). A significant multiplicative interaction was noted between FGF21 (both continuous and dichotomous) and pre-pregnancy BMI (p for interaction = 0.049 and 0.03), and the association was only significant in participants with pre-pregnancy BMI ≥24 kg/m2 . When participants were grouped based on pre-pregnancy BMI (≥24 and <24 kg/m2 ) and FGF21 levels (≥median and

Caffeic acid attenuates tissue damage and inflammatory response in Klebsiella pneumonia by modulating AhR-Src-STAT3-IL-10 signaling pathway.

CA is a plant derivative with antibacterial and antiviral pharmacological effects, however, the therapeutic effect of CA on Klebsiella pneumonia and its mechanism study is still unclear. A rat KP model was established in vitro, a pneumonia cell model was established in vivo, the histopathological changes in the lungs were observed by HE staining after CA treatment, the expression of relevant inflammatory factors was detected by ELISA, the changes in the expression of proteins related to the AhR-Src-STAT3-IL-10 signaling pathway were detected by Western blot and immunofluorescence in the lungs, and the interactions between the proteins were verified by COIP relationship. The results showed that CA was able to attenuate the injury and inflammatory response of lung tissues, and molecular docking showed that there were binding sites between CA and AhR, and COIP demonstrated that AhR interacted with both STAT3 and Ser. In addition, CA was able to up-regulate the expression levels of pathway-related proteins of AhR, IL-10, p-Src, and p-STAT3, and AhR knockdown was able to reduce LPS-induced inflammatory responses and up-regulate pathway-related proteins, whereas CA treatment of AhR-knockdown-treated A549 cells did not show any statistically significant difference compared with the AhR knockdown group, demonstrating that CA exerts its pharmacological effects. These findings elucidated the mechanism of CA in the treatment of KP and demonstrated that CA is a potential therapeutic agent for KP.

ALDH2 mitigates LPS-induced cardiac dysfunction, inflammation, and apoptosis through the cGAS/STING pathway.

BACKGROUND: Sepsis is a severe syndrome of organ dysfunction that often leads to cardiac dysfunction and endangers life. The role of mitochondrial aldehyde dehydrogenase 2 (ALDH2) in LPS-induced myocardial injury is unclear. The purpose of this study was to assess the role of ALDH2 in lipopolysaccharide (LPS)-induced myocardial injury and the regulatory mechanism and to identify potential therapeutic strategies for treating this condition. METHODS: An in vivo model was established by 12 h of LPS (10 mg/kg, intraperitoneal injection) stimulation, and an in vitro model was generated by stimulating H9C2 cells with LPS (10 µg/ml) for 12 h. We then used the ALDH2 activator Alda-1 and the ALDH2 inhibitor daidzin to assess their effects on LPS-induced cardiac injury. Cardiac function in mice was evaluated by using cardiac ultrasound. We used various methods to evaluate inflammation, apoptosis, and oxidative stress, including ELISA, flow cytometry, JC-1 staining, Western blotting, and DCFH-DA staining. Additionally, we used a small interfering RNA (siRNA) to knock down cyclic GMP-AMP synthase (cGAS) to further investigate the relationship between ALDH2 and cGAS in LPS-induced cardiac injury. RESULTS: LPS-induced cardiac dysfunction and increased the levels of the cardiac injury markers creatine kinase-MB (CKMB) and lactate dehydrogenase (LDH) in vivo. This change was accompanied by an increase in reactive oxygen species (ROS) levels, which exacerbated the oxidative stress response and regulated apoptosis through cleaved caspase-3, BAX, BCL-2. The expression of inflammatory cytokines such as IL-6/IL-1ß/TNF-α was also upregulated. However, these effects were reversed by pretreatment with Alda-1 via the inhibition of cGAS/stimulator of interferon genes (STING) signaling pathway. Interestingly, LPS, Alda-1 and daidzin altered the activity of ALDH2 but did not regulate its protein expression. Knocking down cGAS in H9C2 cardiomyocytes alleviated LPS-induced cardiac inflammation, apoptosis, and ROS production and weakened the synergistic effect of daidzin. CONCLUSION: We demonstrated that ALDH2 alleviated LPS-induced cardiac dysfunction, inflammation, and apoptosis through the cGAS/STING signaling pathway, thereby protecting against LPS-induced cardiac injury. This study identifies a novel therapeutic approach for treating sepsis-induced cardiomyopathy (SIC).

Current Status and Influencing Factors of Snakebite Diagnosis and Treatment Knowledge Among Medical Staff in China: A Cross-Sectional Study.

Objectives: This study aimed to determine the current status of the knowledge of diagnosis and treatment of snakebites among medical staff in China and its influencing factors. Methods: A cross-sectional survey of 12,581 medical staff was conducted in 12 provinces in China between June 2022 and February 2023. We analyzed the results using descriptive statistics, T-tests or analysis of variance, and a generalized linear model. Results: The average score of snakebite diagnosis and treatment knowledge among medical staff in China was 3.15 ± 2.15 out of a total score of 12. Through a generalized linear regression model, we found that gender, occupation, region, hospital level, work department, work tenure, training received in the diagnosis and treatment of snakebite, experience in snakebite diagnosis and treatment, availability of antivenom in the unit, and self-evaluation of snakebite treatment ability all affected the medical staff's scores of snakebite diagnosis and treatment knowledge. Conclusion: The knowledge level of snakebite diagnosis and treatment among Chinese medical staff is generally low, so it is imperative to conduct standardized snakebite diagnosis and treatment training for medical staff.

Research Progress on the Relationship Between Sleep Status During Pregnancy and Gestational Diabetes Mellitus.

In recent years, the morbidity of gestational diabetes mellitus (GDM) maintained an upward trend. GDM can't merely lead to negative pregnancy consequences, but also endanger life of the mother and child in severe cases, and may also bring long-term complications and sequelae to the mother and child. Studies using subjective or objective methods to evaluate the correlation between sleep and GDM are inconsistent, but still suggest that poor sleep status may be related to GDM. In order to further understand the current research status of the relationship between sleep measured by different tools and gestational diabetes mellitus, this paper will review the articles from Web of Science, Wanfang, PubMed, VIP, CNKI and other databases.

Current situation and needs analysis of medical staff first aid ability in China: a cross-sectional study.

OBJECTIVES: We aim to understand the current situation of the first aid ability and training needs of Chinese medical personnel to provide a scientific basis for formulating the contents and methods of emergency medical rescue training and thereby improve the first aid level of Chinese medical personnel. METHODS: A cross-sectional survey was conducted between June 2022 and February 2023 using a two-stage cluster sampling method with a structured questionnaire sent to medical workers in 12 provinces in China. 14,527 questionnaires were included in this study. Data were collected on demographic characteristics, first aid knowledge and skills, and training needs. Variance analysis was used to compare the difference between the first aid ability and training needs of medical staff in different hospitals, and multiple linear regression analysis was carried out to evaluate first aid ability and training needs. RESULT: The study included 6041 patients (41.6%) in tertiary hospitals, 5838 patients (40.2%) in secondary hospitals, and 2648 patients (18.2%) in primary hospitals. There were significant differences in the first aid ability and training needs of medical staff in hospitals of different levels (p < 0.001). The score of first aid knowledge and skills in tertiary hospitals was the highest (209.7 ± 45.0), and the score of training needs in primary hospitals was the highest (240.6 ± 44.0). There was a significant correlation between first aid ability and training needs score (p < 0.001). Multiple linear regression analysis shows that geographic region, age, work tenure, gender, job title, department, professional title, monthly income, and hospital level are the influencing factors of training demand. CONCLUSION: Medical staff in primary hospitals generally have low first aid knowledge and skills and a strong willingness to train. Therefore, it is imperative to strengthen the training of first aid ability and research training strategies. The level of the hospital is closely related to the level of first aid, so it is necessary to recognize the commonalities and differences in medical staff's demand for first aid knowledge and skills and carry out targeted education and training.

A Bibliometric Study on Global Snakebite Research Indexed in Web of Science.

Objective: To conduct a bibliometric analysis of the global snakebite literature to provide a reference for the future development of snakebite research. Methods: The Web of Science citation analysis tools, VOSviewer and CiteSpace V were used to carry out the bibliometric analysis of the literature and generate visualization maps. Results: The number of publications has increased at a considerably accelerated rate in the past 8 years. Nine distinct cooperation clusters were formed between institutions and countries. Keyword clustering yielded nine well-structured clusters covering two major topics, i.e., snakebite envenoming and antivenom. Burstiness detection revealed eight keywords with strong emergence, including neglected tropical diseases, Elapidae, Viperidae, and Russell's viper, which have sustained popularity up to the present. Conclusion: Current research on snakebites has gradually garnered attention from the academic community. Cooperation papers between nations severely affected by snakebite and those with higher economic status received more attention. The continued exploration of therapeutic mechanisms, the development of antivenoms or alternative medicines, and primary prevention of snakebites to ensure the safety of populations in impoverished regions should be prioritized by international scholars. The epidemiological evidence and the timely translation of research findings should be valued by policymakers.

Incidence, process of care, and outcomes of out-of-hospital cardiac arrest in China: a prospective study of the BASIC-OHCA registry.

BACKGROUND: Out-of-hospital cardiac arrest (OHCA) is an important global public health issue, but its epidemiology and outcomes in low-income and middle-income countries remain largely unknown. We aim to comprehensively describe the incidence, process of care, and outcomes of OHCA in China. METHODS: In the prospective, multicentre, population-based Baseline Investigation of Out-of-hospital Cardiac Arrest (BASIC-OHCA) registry study, participating sites were selected from both urban and rural areas in all seven geographical regions across China. All patients with OHCA assessed by emergency medical service (EMS) staff were consecutively enrolled from Aug 1, 2019, to Dec 31, 2020. Patients with suspected cardiac arrest assessed by bystanders whose return of spontaneous circulation was achieved without the need for defibrillation or EMS personnel cardiopulmonary resuscitation were excluded. Patients with all key variables missing were excluded, including resuscitation attempt, age, sex, witnessed status, cause, all process of care indicators, and all outcome measures. In this analysis, we included data for EMS agencies serving 25 monitoring sites (20 urban and five rural) that included the entire serving population, data for the whole of 2020, and at least 50 OHCA patients in 2020. Data were collected and reported using the Utstein template. We calculated the crude incidence of EMS-assessed OHCA in 2020. We also report data on baseline characteristics (including sex, cause, location of OHCA, and presence of shockable rhythm), process of care (including EMS response time, cardiopulmonary resuscitation, defibrillation, and advanced life support), and outcomes of non-traumatic OHCA between Aug 1, 2019, and Dec 31, 2020, including survival and survival with favourable neurological outcomes at discharge or 30 days, and at 6 and 12 months. FINDINGS: Of 115·1 million people served by the 25 participating sites, 132 262 EMS-assessed patients with OHCA were enrolled, and resuscitation was attempted for 42 054 (31·8%) patients between Aug 1, 2019, and Dec 31, 2020. The crude incidence of EMS-assessed OHCA was 95·7 per 100 000 population (95% CI 95·6-95·8) in 2020. Among 38 227 individuals with non-traumatic OHCA, 25 958 (67·9%) were male, 30 282 (79·2%) had a cardiac arrest at home, 32 523 (85·1%) had a presumed cardiac cause, and 2297 (6·0%) presented with an initial shockable rhythm. 4049 (11·5%) of 35 090 patients with an unwitnessed or bystander-witnessed OHCA received dispatcher-assisted cardiopulmonary resuscitation and 7121 (20·3%) received bystander cardiopulmonary resuscitation; only 14 (<0·1%) patients were assessed by bystanders with an automated external defibrillator. The median EMS response time was 12 min (IQR 9-16). At hospital discharge or 30 days, 441 (1·2%) of 38 227 survived, 304 (0·8%) survived up to 6 months, and 269 (0·7%) up to 12 months. At hospital discharge or 30 days, 309 (0·8%) survived with favourable neurological outcomes, 257 (0·7%) had favourable neurological outcomes at 6 months, and 236 (0·6%) at 12 months. INTERPRETATION: Our findings revealed a high burden of EMS-assessed OHCA with a low proportion of resuscitation attempts. The suboptimal implementation of chain of survival and unsatisfactory prognosis call for national efforts to improve the care and outcomes of patients with OHCA in China. FUNDING: The National Science & Technology Fundamental Resources Investigation Program of China, the State Key Program of the National Natural Science Foundation of China, Taishan Pandeng Scholar Program of Shandong Province, the Key Research & Development Program of Shandong Province, the Interdisciplinary Young Researcher Groups Program of Shandong University, the Clinical Research Center of Shandong University, the ECCM Program of Clinical Research Center of Shandong University, and the Natural Science Foundation of Shandong Province.