A case control study is a type of observational study. In this study design, participants are selected to participate depending on their outcome status. Cases are participants with outcome of interest whereas controls are participants who do not have the outcome of interest. These studies estimate the odds ratio or the odds between the exposure and health outcome, however they cannot prove causality. Advantages of case control studies include the following: inexpensive, easy to design and implement, and are used to study rare outcomes. Case control studies are prone to certain research bias but can be addressed by the investigator through careful designing and planning. This paper describes the case control studies, their advantages, bias in case control studies and how to address them, and discuss the steps in how to conduct this type of study design.

Pregnancy ; Female ; Humans ; Pre-Eclampsia/epidemiology* ; Prenatal Exposure Delayed Effects ; Case-Control Studies ; China/epidemiology* ; Fluorocarbons/toxicity*

Infant, Newborn ; Humans ; Retrospective Studies ; Case-Control Studies ; Tracheotomy ; Respiration, Artificial

BACKGROUND: It remains unclear whether circulating malondialdehyde (MDA) levels change in people with diabetic retinopathy (DR). This systematic review compared circulating MDA levels in diabetic people with and without DR. METHODS: PubMed, Medline (Ovid), Embase (Ovid), and Web of Science were searched for case-control studies conducted before May 2022 in English that compared circulating MDA levels in people with and without DR. The following MeSH search terms were used: ("malondialdehyde" or "thiobarbituric acid reactive substances [TBARS]" or "lipid peroxidation" or "oxidative stress") and "diabetic retinopathy." Newcastle-Ottawa Quality Assessment Scale was used to evaluate the quality of the included studies. Random-effects pairwise meta-analysis pooled the effect size with standardized mean difference (SMD) and 95% confidence intervals (CIs). RESULTS: This meta-analysis included 29 case-control studies with 1680 people with DR and 1799 people with diabetes but not DR. Compared to people without DR, the circulating MDA levels were higher in those with DR (SMD, 0.897; 95% CI, 0.631 to 1.162; P  < 0.001). The study did not identify credible subgroup effects or publication bias and the sensitivity analysis confirmed the robustness of the study. CONCLUSIONS: Circulating MDA levels are higher in people with DR compared to those without. Future comparative studies that use more specific methods are required to draw firm conclusions. REGISTRATION PROSPERO; https://www.crd.york.ac.uk/PROSPERO/ ; No. CRD42022352640.
Humans ; Diabetic Retinopathy ; Malondialdehyde ; Oxidative Stress ; Case-Control Studies ; Diabetes Mellitus

Child ; Humans ; Case-Control Studies ; East Asian People ; Genetic Predisposition to Disease/genetics* ; Methyltransferases/genetics* ; Polymorphism, Genetic ; Wilms Tumor/pathology*

OBJECTIVE: This study prospectively investigates the association between immunoglobulin G (IgG) N-glycan traits and ischemic stroke (IS) risk. METHODS: A nested case-control study was conducted in the China suboptimal health cohort study, which recruited 4,313 individuals in 2013-2014. Cases were identified as patients diagnosed with IS, and controls were 1:1 matched by age and sex with cases. IgG N-glycans in baseline plasma samples were analyzed. RESULTS: A total of 99 IS cases and 99 controls were included, and 24 directly measured glycan peaks (GPs) were separated from IgG N-glycans. In directly measured GPs, GP4, GP9, GP21, GP22, GP23, and GP24 were associated with the risk of IS in men after adjusting for age, waist and hip circumference, obesity, diabetes, hypertension, and dyslipidemia. Derived glycan traits representing decreased galactosylation and sialylation were associated with IS in men (FBG2S2/(FBG2 + FBG2S1 + FBG2S2): odds ratio ( OR) = 0.92, 95% confidence interval ( CI): 0.87-0.97; G1 ⁿ: OR = 0.74, 95% CI: 0.63-0.87; G0 ⁿ: OR = 1.12, 95% CI: 1.03-1.22). However, these associations were not found among women. CONCLUSION This study validated that altered IgG N-glycan traits were associated with incident IS in men, suggesting that sex discrepancies might exist in these associations.
Male ; Humans ; Female ; Immunoglobulin G/metabolism* ; Ischemic Stroke ; Case-Control Studies ; Cohort Studies ; Glycosylation ; Polysaccharides

Objective To investigate the effect of systematic graded rewarming pattern on all-cause mortality of hypothermic trauma patients in different time periods. Methods A prospective case-control study was carried out for 236 hypothermic trauma patients with modified trauma score<12 in the Emergency Department of the Second Affiliated Hospital of Wenzhou Medical University from January 2020 to December 2021.The patients were randomly assigned into a systematic graded rewarming group (n=118) and a traditional rewarming group (n=118).The main outcome event was all-cause death within 15 days after trauma,and the secondary outcome event was all-cause death within 3,7,and 30 days after trauma. Results Overall,13.98%(33/236) and 14.83%(35/236) of the patients died within 15 and 30 days after trauma,respectively,and the median survival time of all dead patients was 6 (4,10) days.The systematic graded rewarming group had higher temperature after rewarming for 2 h (P=0.001) and larger temperature change after rewarming intervention (P=0.047) than the traditional rewarming group.The all-cause mortality within 15 days (27.3%vs.72.7%,P=0.005) and 30 days (25.7%vs.74.3%,P=0.002) in the systematic graded rewarming group was lower than that in the traditional rewarming group.Kaplan-Meier analysis showed that the survival time of the patients in the systematic graded rewarming group was longer than that in the traditional rewarming group (P=0.003).Multivariate cox regression analysis indicated that systematic graded rewarming was a strong protective factor for survival time after trauma (HR=0.450, P=0.042).Further Logistic regression analysis for the occurrence of all-cause death in each time period showed that the OR of systematic graded rewarming pattern to all-cause death within 15 days and 30 days after trauma were 0.289 and 0.286,respectively,after adjusting the covariates(P=0.008,P=0.005).The temperature after rewarming for 2 h had a negative correlation with all-cause mortality within 30 days after trauma (OR=0.670, P=0.049). Conclusions Systematic graded rewarming is a protective factor for the survival time of patients with traumatic hypothermia and an independent factor affecting the risk of all-cause death within 15 days and 30 days after trauma.The temperature after rewarming for 2 h is expected to be an independent predictor of all-cause mortality of 30 days after trauma in the patients with hypothermia.The systematic graded rewarming pattern could reduce the mortality of hypothermic trauma patients.
Humans ; Hypothermia ; Rewarming ; Case-Control Studies

Objective To explore the relationship between scavenger receptor class B member 1 (SCARB1) gene promoter methylation and the pathogenesis of coronary artery disease. Methods A total of 120 patients with coronary heart disease treated in Renji Hospital affiliated to Shanghai Jiao Tong University School of Medicine from December 2018 to May 2020 were selected as the case group,while 140 gender and age matched healthy participants were randomly selected as the control group for a case-control study.The methylation status was detected by high-throughput target sequencing after bisulfite converting,and the methylation of CpG sites in the promoter region of SCARB1 gene was compared between the two groups. Results The case group showed higher methylation level of SCARB1+67 and lower methylation level of SCARB1+134 than the control group (both P<0.001),and the differences remained statistically significant in men (both P<0.001) and women (both P<0.001).The overall methylation level in the case group was lower than that in the control group [(80.27±2.14)% vs.(81.11±1.27)%;P=0.006],while this trend was statistically significant only in men (P=0.002). Conclusion The methylation of SCARB1 gene promotor is associated with the pathogenesis and may participate in the occurrence and development of coronary heart disease.
Male ; Humans ; Female ; Methylation ; Case-Control Studies ; China ; Coronary Artery Disease/genetics* ; Promoter Regions, Genetic ; DNA Methylation ; Scavenger Receptors, Class B/genetics*

Clinical efficacy is the basis for the development of traditional Chinese medicine(TCM), and the evaluation of clinical efficacy of TCM has always been the focus of attention. The technical and methodological difficulties in the evaluation process often restrict the generation of high-level evidence. Therefore, methodological research should be deepened and innovative practice should be carried out to study the application of scientific research methods in the evaluation of the advantages of TCM. After more than ten years of development, the clinical efficacy evaluation of TCM, on the basis of the initially classic placebo randomized controlled trials, has successively carried out a series of meaningful attempts and explorations in N-of-1 trials, cohort studies, case-control studies, cross-sectional studies, real world studies, narrative medicine studies, systematic evaluation, and other aspects, laying the foundation for the transformation of TCM from "experience" to "evidence". This paper focused on the clinical efficacy evaluation of TCM, summarized the main connotation and development status of efficacy evaluation indicators, standards, and methods, and put forward corresponding countermeasures and suggestions for the problems of indicator selection, standard formulation, and methodology optimization in the research process. It is clear that scientific and objective evaluation of the efficacy of TCM is an urgent problem to be solved at present.
Medicine, Chinese Traditional ; Cross-Sectional Studies ; Treatment Outcome ; Case-Control Studies ; Narrative Medicine

OBJECTIVE: To explore relationship between bone marrow edema(BME) and osteoporosis in patients with severe knee osteoarthritis. METHODS: Unmatched case-control study was conducted. Totally 160 patients with severe knee osteoarthritis who had undergone knee magnetic resonance imaging (MRI) and bone mineral density examination (BMD) from January 2020 to March 2021 were included. Eighty patients complicated with BME were included in BME group, and 80 patients without BME were selected as NBME group. In BME group, there were 12 males and 68 females, aged from 51 to 80 years old with an average of(66.58±8.10) years old;the courses of disease ranged from 5 to 40 months with an average of (15.61±9.25) months;body mass index(BMI) ranged from 21.81 to 34.70 with an average of (27.79±3.00) kg·m^-2;25 patients classified to grade Ⅲ and 55 patients grade Ⅳ according to Kellgren- Lawrence(K-L). In NBME group, there were 15 males and 65 females, aged from 50 to 80 years old with an average of(67.82±8.05) years old;the course of disease ranged from 6 to 37 months with an average of(15.75±8.18) months;BMI ranged from 21.39 to 34.46 with an average of (28.26±3.13) kg·m^-2;25 patients were K-L Ⅲ and 55 patients with K-L Ⅳ. The degree of bone marrow edema was evaluated by knee whole oragan magnetic resonance imaging score(WORMS). Osteoporosis was diagnosed and BMD was evaluated by DXA T value. To explore the relationship between bone marrow edema and osteoporosis by comparing prevalence rate of osteoporosis between two groups, and to further explore relationship between BME and BMD by Spearman correlation analysis of BME WORMS score and DXA T value in BME group. RESULTS: The complete case data were obtained on the first diagnosis, and there was no significant difference in sex, age, courses of disease and BMI between two groups (P>0.05). The proportion of K-L Ⅳ in BME group was significantly higher than that in NBME (P<0.05). The prevalence rate of osteoporosis in BME group was significantly higher than in NBME group with the same K-L grade (P<0.001), and there was a strong negative correlation between BME WORMS score and DXA BMD T value (r=-0.812, |r|=0.812 >0.8, P<0.001). CONCLUSION Osteoporosis is one of the risk factors of bone marrow edema in patients with severe knee osteoarthritis, and the lower the bone mineral density is, the easier it is to be complicated with bone marrow edema.
Male ; Female ; Humans ; Osteoarthritis, Knee/diagnostic imaging* ; Bone Marrow/pathology* ; Case-Control Studies ; Bone Marrow Diseases/etiology* ; Osteoporosis/complications* ; Edema/etiology* ; Magnetic Resonance Imaging/methods*