Diarrhea ; Cities ; Epidemiologic Causality

Measurement bias (MB) has been described in causal structures but is still not entirely clear. In practice, the correctness of substitution estimate (SE) of effect is a prerequisite for causal inference, usually based on a bidirectionally non-differential misclassification between the measured exposure and the measured outcome. Based on a directed acyclic graph (DAG), this paper proposes a structure for the single-variable measure, where its MB is derived from the choice of an imperfect, "input/output device-like" measurement system. The MB of the SE is influenced both by the measurement system itself and by factors outside the measurement system: while the independence or dependence mechanism of the measurement system still ensures that the MB of the SE is bidirectionally non-differential; however, the misclassification can be bidirectionally non-differential, unidirectionally differential, or bidirectionally differential resulted from the factors outside the measurement system. In addition, reverse causality should be defined at the level of measurement, where measured exposures can influence measured outcomes and vice versa. Combined with temporal relationships, DAGs help elucidate MB's structures, mechanisms, and directionality.
Humans ; Confounding Factors, Epidemiologic ; Data Interpretation, Statistical ; Bias ; Causality

The overall details of causality frames in the objective world remain obscure, which poses difficulty for causality research. Based on the temporality of cause and effect, the objective world is divided into three time zones and two time points, in which the causal relationships of the variables are parsed by using Directed Acyclic Graphs (DAGs). Causal DAGs of the world (or causal web) is composed of two parts. One is basic or core to the whole DAGs, formed by the combination of any one variable originating from each time unit mentioned above. Cause effect is affected by the confounding only. The other is an internal DAGs within each time unit representing a parent-child or ancestor-descendant relationship, which exhibits a structure similar to the confounding. This paper summarizes the construction of causality frames for objective world research (causal DAGs), and clarify a structural basis for the control of the confounding in effect estimate.
Causality ; Computer Graphics ; Confounding Factors, Epidemiologic ; Data Interpretation, Statistical ; Epidemiologic Methods ; Humans

One of the commonly accepted merits of cohort studies (CSs) refers to the exposure precedes outcome superior to other observational designs. We use Directed Acyclic Graphs to construct a causal graph among research populations under CSs. We notice that the substitution of research population in place of a susceptible one can be used for effect estimation. Its correctness depends on the outcome-free status of the substituted population and the performance of both screening and diagnosis regarding the outcomes under study at baseline. The temporal precedence of exposure over outcome occurs theoretically, despite the opposite happens in realities. Correct effect estimate is affected by both the suitability of population substitution and the validities of outcome identification and exclusion.
Causality ; Cohort Studies ; Confounding Factors, Epidemiologic ; Epidemiologic Methods ; Mass Screening ; Research Design

Confounding affects the causal relation among the population. Depending on whether the confounders are known, measurable or measured, they can be divided into four categories. Based on Directed Acyclic Graphs, the strategies for confounding control can be classified as (1) the broken-confounding-path method, which can be further divided into single and dual broken paths, corresponding to exposure complete intervention, restriction and stratification, (2) and the reserved-confounding-path method, which can be further divided into incomplete exposure intervention (in instrumental variable design and non-perfect random control test), mediator method and matching method. Among them, random control test, instrumental variable design or Mendelian randomized design, mediator method can meet the requirements for controlling all four types of confounders, while the restriction, stratification and matching methods are only applicable to known, measurable and measured confounders. Identifying the mechanisms of confounding control is a prerequisite for obtaining correct causal effect estimates, which will be helpful in research design.
Causality ; Confounding Factors, Epidemiologic ; Humans ; Models, Statistical ; Random Allocation ; Randomized Controlled Trials as Topic ; Research Design

PURPOSE: Alternaria spp. is opportunistic fungus and the most prevalent cause of asthma and allergic disease. Keratitis caused by the fungus Alternariaspp. is quite rare. The authors performed an epidemiological study to identify the risk factor and to evaluate clinical manifestations, methods and results of treatment in Alternaria keratitis. METHODS: Epidemiological study of Alternaria keratitis was performed prospectively under the identical protocol from April 1995 to May 2000 in 5 hospitals. RESULTS: Seven cases of Alternaria keratitis were identified by culture with corneal scraping or corneal biopsy. They were 8.5% of the 82 cases of fungal keratitis. Of the 7 patients, 5 were men (71.4%). All patients were over 50 years and 5 of them (71.4%) were farmers. In terms of trauma history, 6 out of 7 patients had previous history of corneal traumas, and most of these corneal traumas were vegetable matter-related. CONCLUSIONS: The most common (83.3%) predisposing factor for Alternaria keratitis was vegetable matter-related corneal trauma. The prompt referral for diagnostic studies and specific antifungal management, or surgical therapy might be helpful to reduce the incidence rate of complication of keratomycoses.
Alternaria* ; Asthma ; Biopsy ; Causality ; Epidemiologic Studies* ; Fungi ; Humans ; Incidence ; Keratitis* ; Male ; Prospective Studies ; Referral and Consultation ; Risk Factors ; Vegetables

Dermatoglyphics has been studied in various diseases including mongolism, ruhella syndrome, congenital heart disease, selected neurologic diseases and other disorders. However, reports of derrnatoglyphic studies in patients with leprosy have not been evcountered a lot. Although Ieprasy is an infectious disease due to the hfycobacterium leprae, the hereditary susceptibility of the host to the organism is proposed as an additional predisposing factor. Thia concept has been proposed to reconcile the low incidence of lisease among large numbers of contacts. Most reports delving into the role of heredity in leprosy have been related ta epidemiological studies. Prasad and Mohamad suggest, on the basis of data related to rnultiple patient families, that the acquisition of leprosy may be determined genetically on the assumption of incomplete dominance of genes; on the other hand, Spickett suggested that if there is any genetic effect, it is but a component af the familial effect. This study of dennatoglyphics in 77 male leprosy patients was undcataken to determine if there might be significance in the analysis of dermal patterns af the hands as related to the hereditary susceptibility of individuals to the disease comparing with those of 234 healthy Korean soldiers. Results are as follows: 1. In the analysis of the total fingertip ridges, there is significant difference (P<0.01) between the leprosy (137.66+4.7) and the control group (152.93+9.50). 2. A aignificant statistical difference between the leprosy and the control group (14.73+2.79) does not exist with respect to the pattern intensity, however that af the borderline group of leprosy (12.00+5.09)is decreased (P<0.025). 3. In the incidence of simian lines, the leprosy group (5.20%) shows lower incidence rate than that of control group (8.98%). 4. As for the a-b ridge count, it is decreased significantly (P<0.05) in the left hand of leprosy group (34.71+0.87) than that of the eontrol group (37.11+0.52), Also there is significant difference(P<0. 05) in the right hands of tuberculoid type of leprosy (34.64+1.38). 5. With respect to the propoetional distance (mm.) between the distal flexion crease of the wrist to the base of the middle finger with the distance (mm.) of the same point of the wrist to the axial triradius, a significant statistical difference between the leprosy and the control group does not exist, but significantly longer distance (mm.) exists in the tuberculoid type of leprosy (P<0.05). 6. No significant fingertip pattern differences are noted between the leprosy and the control group.
Causality ; Communicable Diseases ; Dermatoglyphics* ; Down Syndrome ; Epidemiologic Studies ; Fingers ; Hand ; Heart Defects, Congenital ; Heredity ; Humans ; Incidence ; Korea* ; Leprosy* ; Male ; Military Personnel ; Wrist

BACKGROUND: Eczema herpeticum (EH) is caused by viral infection, usually with the herpes simplex virus (HSV), and most often occurs in patients with atopic dermatitis (AD). Although EH is a common dermatosis, predisposing factors are largely unknown, and there have been few clinical and epidemiologic studies in Korea. OBJECTIVE: This study evaluated the clinical characteristics of inpatients diagnosed with EH over the last 10 years. METHODS: We reviewed the medical records of 62 patients who were diagnosed with EH and were hospitalized at the Chonnam National University Hospital in Gwangju from January 2004 to July 2014. RESULTS: The ratio of male to female patients with EH was about 2:1, and the mean age at onset of EH was 25.3 (+/-17.3) years. In this study, AD (67.7%) was the most common preceding skin disorder, followed by nummular eczema (6.5%), and seborrheic dermatitis (3.2%). Patients with EH had other systemic symptoms such as fever (22.6%), headache (4.8%), and lymphadenopathy (4.8%). Patients with recurrent infection of HSV had longer hospitalizations compared to those with primary infection (9.35 vs. 6.49 days), but the difference was not significant (p=0.269). There was no significant difference in the number of hospitalized days between patients receiving antiviral agents vs. antibiotics (p=0.153). Systemic steroids were administered in 66.1% patients, which had no correlation with the number of hospitalized days (p=0.203). CONCLUSION: The present retrospective analysis contributes to our understanding of the clinical characteristics of EH.
Anti-Bacterial Agents ; Antiviral Agents ; Causality ; Dermatitis, Atopic ; Dermatitis, Seborrheic ; Eczema* ; Epidemiologic Studies ; Female ; Fever ; Gwangju ; Headache ; Hospitalization ; Humans ; Inpatients* ; Jeollanam-do ; Kaposi Varicelliform Eruption* ; Korea ; Lymphatic Diseases ; Male ; Medical Records ; Retrospective Studies ; Simplexvirus ; Skin ; Skin Diseases ; Steroids

BACKGROUND: Rosacea is well recognized as a chronic cutaneous disorder primarily of the convexities of the central face. Despite its apparent high incidence, the nosology of rosacea is not well established in Korea. OBJECTIVE: The purpose of this epidemiological study was to investigate the clinical manifestations of Korean rosacea patients diagnosed by the US National Rosacea Society guidelines of US. METHODS: We performed a clinical study in 90 patients with rosacea who visited the Department of Dermatology, Korea University Ansan Hospital from January 2005 to December 2006. These patients were evaluated with regard to age, sex, primary/secondary features, clinical subtypes and predisposing factors. RESULTS: The ratio of males to females was 1 : 1.3. The age distribution showed a peak incidence in the fifth decade. Primary features of rosacea were telangiectasia (70.0%), nontransient erythema (68.9%), papules and pustules (62.2%) and flushing (61.1%). The most common secondary features of rosacea were burning and stinging (62.2%). Other secondary features were dry appearance (46.7%), edema (35.6%), plaque (20.0%), phymatous changes(18.9%), ocular manifestations (17.8%) and peripheral location (2.2%). The most common subtype was erythematotelangiectatic rosacea (51.1%), followed by papulopustular rosacea (34.4%), phymatous rosacea (12.2%) and ocular rosacea (2.2%). The majority of rosacea patients revealed mild symptoms (83.3%). Predisposing or exacerbating factors of rosacea were stress (52.2%), hot baths (46.7%), alcohol (44.4%), hot weather (42.2%), sun exposure (38.9%), exercise (35.6%), cold weather (25.5%), skin-care products (23.3%), spicy foods (21.1%), indoor heat (15.6%), heated beverages (12.2%) and humidity (4.4%). CONCLUSION: In this study, the National Rosacea Society classification system applied well to Korean patients. We identified female predominance, a peak in the fifth decade and the majority of Korean rosacea patients suffering from the erythrotelangiectatic type of rosacea. Other similarities and differences to previous reports were also discussed.
Age Distribution ; Baths ; Beverages ; Bites and Stings ; Burns ; Causality ; Classification ; Dermatology ; Edema ; Epidemiologic Studies ; Erythema ; Female ; Flushing ; Gyeonggi-do ; Hot Temperature ; Humans ; Humidity ; Incidence ; Korea ; Male ; Rosacea* ; Solar System ; Telangiectasis ; Weather