1. Epidemiological concept? 2. Task? 3. Classification of research methods? 4. Common indicators? 5. Common research methods?
The study of the distribution, influence and decisive factors of diseases, health conditions and events in the population, so as to prevent and control diseases and promote health.
1. The first stage-revealing the phenomenon
2. The second stage-find out the reason, influence or decisive factor.
3. The third stage-providing measures
Combined with health management, the corresponding measures are: health information collection, health risk assessment, health guidance and health risk factor intervention.
(1) ratio and ratio
1. Proportion-refers to the quantitative proportion between parts of the same thing and the whole, usually expressed by p = a/(a+b).
2. Rate-refers to the ratio of the actual number of cases of a phenomenon to the total number of cases that may occur under certain conditions, which is used to explain the frequency or intensity of a phenomenon in unit time. Rate = (the actual number of cases of a phenomenon/the total number of people who may have the phenomenon) ×k, k= 100%, 0.000%, 0.0000%, 0.0000%, 0.0000%, 0.0000%.
3. Rate composition: the number of people affected, the total number of people affected by observation, and the specified time.
4. Ratio-also called relative ratio, means the value obtained by dividing two numbers and their relative level. Formula: ratio = indicator A/ indicator B? 100% (added)
(2) Incidence index
1. Incidence
(1) refers to the frequency of new cases of a certain disease in a certain period of time. Formula: Incidence rate = (number of new cases of a certain disease in a certain population in a certain period/number of exposed population in the same period)? k
(2) The exposed population-also known as the dangerous population-refers to people who may have diseases to be observed in the observation area during the observation period.
(3) Use-It is particularly important for infectious diseases and diseases with extremely low mortality or non-fatal diseases, reflecting the danger of diseases; It is often used to describe the distribution of diseases, explore pathogenic factors, put forward etiological hypothesis and evaluate the effect of prevention and control measures.
2. Prevalence rate
(1), also known as prevalence rate and prevalence rate, refers to the ratio of new cases to old cases of a certain disease in a certain population in a specific time. Prevalence rate = (number of new and old cases of a disease in a certain population at a specific time point/observed population in the same period)? k
(2) Influencing factors: incidence and course of disease.
(3) Use-It can provide some valuable information about the epidemic situation of chronic diseases with a long course, and can reflect the disease distribution in a certain area and the disease burden of a certain disease. According to the prevalence rate, we can reasonably plan the demand of health facilities, manpower, material resources and health resources, study the epidemic factors of diseases and monitor the control effect of chronic diseases.
3. Difference between prevalence and incidence
(1) The numerator of the prevalence rate is the number of old and new cases of a certain disease in the investigated population at a specific time, regardless of the onset time of these cases; The molecule of incidence rate is the number of new cases among exposed people in a certain period;
(2) The prevalence rate is the frequency of diseases obtained from cross-sectional surveys, and it is a static indicator to measure the existence or prevalence of diseases. It is actually a ratio, not a real ratio. Incidence rate is the frequency and intensity of diseases in unit time obtained from incidence reports or cohort studies. It is a dynamic index and a real ratio.
(3) Death index
1. Lethal rate
(1) refers to the proportion of people who died of various causes per unit time, and is the most commonly used indicator to measure the risk of death. Mortality rate = (the total number of deaths of a certain population in a certain year/the average population of that population in that year)? K, where k= 100,000 per thousand or 100,000 per thousand.
(2) Classification: crude mortality-mortality caused by all causes is unadjusted mortality; Specific mortality-mortality calculated by disease type, age, sex, occupation, race, etc.
2. Mortality rate
(1) indicates the proportion of all patients with a certain disease who died of the disease in a certain period of time. Mortality is different from mortality. Mortality is not a real ratio, but a ratio. Mortality rate = (number of deaths due to a certain disease in a certain period/number of cases diagnosed as a certain disease in the same period)? 100%
(2) Mortality rate is usually used for acute diseases with short course of disease to measure the threat to human life.
3. Survival rate
(1), also known as survival rate, refers to the proportion of patients suffering from certain diseases (or patients receiving certain treatment measures) who have been followed up for n years, and the proportion of cases that are still alive at the end of follow-up to the number of observed cases.
(2)n-year survival rate = (number of disease survivors/number of disease cases followed up for N years)? 100%
(4) Relative risk
1. Relative risk degree
(1), also called ratio ratio (RR), refers to the ratio of the incidence (Ie) of exposed group to the incidence (io) of non-exposed group, which reflects the degree of correlation between exposure and disease. Calculation formula RR=Ie/Io
(2) significance-explain how many times the risk of the exposed group is than that of the unexposed group.
(3)RR is unitless, and the ratio ranges from 0 to positive infinity. The greater the ratio, the stronger the connection.
RR= 1, and there is no connection between exposure and disease. RR < 1, negatively correlated, and exposure was a protective factor; RR > 1, positively correlated, and exposure was a risk factor.
2. Ratio ratio
(1) is also called dominance ratio and cross product ratio (OR). Refers to the ratio of exposed persons to unexposed persons in case group divided by the ratio of exposed persons to unexposed persons in control group.
(2) Like RR, OR reflects the higher risk of illness in exposed people than in unexposed people.
(3) If the following two conditions can be met, the OR value is close to or even equal to the RR value: the morbidity (mortality) of the studied disease is very low, and the selected subjects are representative.
(5) Attributable risk
1. Attributable risk degree
(1) is also called rate difference, abbreviated as AR. Refers to the difference of incidence rate between exposed group and non-exposed group, which reflects the degree to which the incidence rate is attributed to exposure factors. Formula: AR=Ie-Io=Io(RR- 1)
(2) Significance: refers to the morbidity or mortality caused by an exposure factor in the exposed population.
2. Percentage of attributable risk
Abbreviation of (1): AR% refers to the percentage of cases caused by exposure factors in all cases. Formula: AR%=(Ie-Io)/Ie, and then × 100%.
(2) The higher the value, the more important the intervention.
3. Percent of population attributable risk
(1) is abbreviated as PAR%, indicating the proportion of exposure-induced diseases in the whole population. The formula 1: PAR% = (It-IO)/IT, and then × 100% is the incidence of the whole population.
(2) Hygienic significance: the extent to which the incidence (or mortality) of a certain disease in the population may decrease after the exposure factors are completely controlled.
(1) current situation investigation
1. Concept: refers to the collection of data about variables, diseases or health status in a specific time by means of general survey or sampling survey in a certain population, so as to describe the current distribution of diseases or health status and the correlation between a certain factor and diseases. Because it was completed in a certain time or in a short time, this world point is like a cross section, so it is also called cross-sectional study.
2. Objective: (1) to describe the distribution of diseases or health conditions; (2) looking for clues of etiology; (3) Secondary prevention of adaptive diseases; (4) Evaluate the preventive and therapeutic effects of diseases; (5) monitoring diseases; (6) Others: measure the health level and health status of a country or region, study the demand for health services, and make community health plans.
3. Classification: general survey and sampling survey (divided into non-random sampling and random sampling)
4. Advantages and disadvantages
(1) Advantages: Sampling survey is a commonly used method in current survey, and the reliability of estimating the population with samples is high, so its research results have strong promotion significance. At present, the situation study is to collect play data, and then compare the samples according to whether they are exposed or sick, that is, there are naturally formed control groups from the same group, so the results are comparable. Questionnaire survey or sampling monitoring is used in the research process, so many factors can be observed at the same time in one survey, which is one of the indispensable basic work in the process of exploring the cause.
(2) Limitations: The time correlation between antecedents and consequences is difficult to determine. Incidence data are not available. It is possible to underestimate the disease level of this research group.
(b) group studies
1. Concept: Also called group learning. It is an observational research method, which divides a specific population into n groups or queues according to whether they are exposed to a certain factor or different exposure levels, and follows up for a period of time to compare the differences in morbidity or mortality between two groups or groups, so as to test whether there is a causal connection between the factor and a certain disease and the strength of the connection. It can be used to test the hypothesis of etiology, evaluate the preventive effect and study the natural history of diseases.
2. Types: prospective cohort study, historical cohort study and bidirectional cohort study (mixed cohort study).
3. Characteristics
(1) is from front to back in time sequence, and it started before the onset, so it is a prospective study.
(2) It is an observational comparative study.
(3) Subjects are grouped according to exposure or not, which is different from the random classification of experimental research.
(4) It is a study from "cause" to "effect".
(5) Follow-up observation of the difference in morbidity or mortality between the two groups.
4. Advantages and disadvantages
(1) Advantages: Before the disease occurs, patients are grouped according to whether they are exposed to certain factors, and the obtained data are complete, and there is no memory bias. You can calculate the incidence of exposure group and non-exposure group, and measure the specific risk and relative risk between the two groups. The influence of exposure factors can be graded, which is convenient for calculating the dose-effect relationship. The sample size is large and the results are stable. In the case of complete data records, a retrospective historical cohort study can be carried out.
(2) Limitations: long observation time, high labor intensity and high cost. The design is scientific and the implementation is difficult. The study of rare diseases needs a large number of subjects, and it is difficult to collect complete and reliable data, which is not suitable for the study of rare diseases.
(3) Case control study
1. Concept: Select a group of patients with the studied disease and a group of control group without the disease, investigate their exposure to certain factors before the onset, compare the differences of exposure rate and exposure level between the two groups, and study the relationship between the disease and these factors.
2. Features
(1) was carried out after the onset of the disease, and there were several cases at the beginning of the study.
(2) The subjects were divided into case group and control group according to the onset or not.
(3) Obtain the exposure of the studied factors through retrospective investigation or information collection.
(4) If the causal relationship is analyzed, the result has already occurred, which is the reasoning order of causality.
(5) By comparing the exposure rate and exposure level between the two groups, the relationship between exposure and diseases was analyzed.
3. Advantages and disadvantages
Advantages of (1): small sample size, easy case acquisition, easy implementation and quick effect. It is suitable for diseases with complex etiology, low incidence and long incubation period. The curative effect and side effects of the treatment measures can be preliminarily evaluated.
(2) Limitations: It is often difficult to judge the time sequence of exposure factors and diseases, so it is impossible to determine the causal relationship. Incidence, mortality and relative risk cannot be calculated. It is easy to produce selection bias when choosing the research object, and it is easy to produce information bias (recall bias) when retrospective investigation.
(4) Experimental research
1. Basic properties: The researcher grasps the experimental conditions to a certain extent and actively gives some intervention measures to the research object. Also known as intervention research.
2. Types: clinical trials, field trials, community trials and similar trials.
3. Features: Prospective study, random grouping, establishment of control group and intervention measures.
4. Clinical trials
(1) is a clinical trial to evaluate the efficacy of new drugs and new therapies, and it is the last human application trial before the formal application of clinical treatment measures.
(2) According to the principle of random distribution, the subjects were divided into experimental group and control group, the former was given some treatment measures, and the latter was not given this measure or placebo, and the effect and value of this measure were evaluated after a period of time.
(3) The purpose of clinical trial is to observe and demonstrate the effect or influence of one or some research factors on the research object.
5. Community trial: also known as lifestyle intervention trial, is an experimental observation of people who have never suffered from the studied disease as a whole, and is often used to evaluate or evaluate some preventive measures or methods.
(v) Evaluation and research of diagnostic tests.
1. Concept: Diagnostic test is a test method to diagnose diseases.
2. Diagnostic indicators: objective indicators, subjective indicators and semi-objective indicators.
3. Methods to determine diagnostic criteria: biostatistics, clinical judgment and ROC curve.
4. Evaluation index of diagnostic test
5. Evaluation criteria of diagnostic test
(1) Comparison between synchronous blind method and gold standard diagnosis method;
(2) the representativeness of the research object;
(3) There should be enough sample size;
(4) The determination of diagnostic threshold should be reasonable;
(5) Not only the authenticity but also the reliability should be evaluated;
(6) Test methods and steps should be specific and operable.
6. Methods to improve the quality of diagnosis
(six) evaluation and research of screening test.
1. Concept: Screening test distinguishes people who may be sick but look healthy from those who may not be sick through rapid examination, examination or other measures.
2. Use: early detection of pre-clinical or early clinical suspicious patients; High-risk individuals who find certain diseases; Carry out epidemiological monitoring; Understand the natural history of diseases.
3. Type: According to the range of screening objects, it can be divided into group screening and selective screening.
4. Methods: Single screening and multiple screening.
5. It is suggested that screening methods for hypertension, diabetes, overweight and obesity, chronic obstructive pulmonary disease and chronic diseases such as cervical cancer, breast cancer, colorectal cancer, liver cancer and nasopharyngeal carcinoma are relatively mature, and tumors with good therapeutic effect can be found early.