Epidemiology in Community Health Care

Epidemiology in Community Health Care Epidemiology in Community Health Care Prepared by Suhail AL Humoud

Epidemiology in Community Health Care: objective After completion the lecture the students enable to: • Explore the historical roots of epidemiology. • Explain the host, agent, and environment model. • Describe theories of causality in health and illness. • Explain a “web of causation” matrix that assists you with recognition of multicausal factors in disease or injury occurrences. • Define immunity and compare passive immunity, active immunity, • cross-immunity, and herd immunity. • Explain how epidemiologists determine populations at risk. • Identify the four stages of a disease or health condition. • List the major sources of epidemiologic information. • Distinguish between incidence and prevalence in health and • illness states. • Use epidemiologic methods to describe an aggregate’s health. • Discuss the types of epidemiologic studies that are useful for • researching aggregate health. • Use the seven-step research process when conducting an • epidemiologic study.

definition • DEFINITION • Epidemiology is the study of the determinants and distribution of health, disease, and injuries in human populations. • It is a specialized form of scientific research that can provide health care workers, including community health nurses, with a body of knowledge on which to base their practice and methods for studying new and existing problems.

Definition …. Cont • Epidemiologists • What is the occurrence of health and disease in a population? • Has there been an increase or decrease in a health state over the years? • Does one geographic area have a higher frequency of disease than another? • What characteristics of people with a particular condition distinguish them from those without the condition? • What factors need to be present to cause disease or injury? • Is one treatment or program more effective than another in changing the health of affected people? • Why do some people recover from a disease and others do not?

Definition …. Cont • Health Indictors • Definition: • Health indicators are standardized measures by which to compare health status and health system performance and characteristics among different jurisdictions in country

Definition …. Cont • Categories of Health Indictors • Categories of health indictors • Mortality and burden of disease Ex: Access data on life expectancy, child mortality, morbidity.. • Health services coverage Ex: Access data on skilled birth attendance, antenatal care, TB detection/treatment... • Health systems resources Ex: Access data on health workforce, hospital beds and health expenditure. • Risk Factors Ex: Access data on water and sanitation, nutrition, tobacco use... • Inequities Ex: Access data on inequities in health care and health outcome. • Demographic and socioeconomic statistics as:Access data on total population, birth/death registration

Goal of the epidemiology Goal of the epidemiology • The ultimate goals of epidemiology are to: • determine the scale and nature of human health problems, • identify solutions to prevent disease, and • improve the health of the entire Population • Epidemiology offers community health nurses a specific methodology for assessing the health of aggregates. Furthermore, it provides a frame of reference for investigating and improving clinical practice in any setting.

Goal of the epidemiology … cont • For example, if a community health nursing goal is to lower the incidence of sexually transmitted diseases (STDs) in a given community, such a prevention plan requires information about population groups. • How many STD cases have been reported in this community in the past year? • What is the expected number of STD cases (the morbidity rate)? • Which members of the community are at highest risk of contracting STDs? • Any program of screening, treatment, or health promotion regarding STDs must be based on this kind of information about population groups to be effective.

Goal of the epidemiology • Florence Nightingale, the first nurse epidemiologist, pioneered the use statistics to improve public health. During the Crimean War, Nightingale collected data and systemized record-keeping practices to improve hospital conditions. She invented pie charts, and other graphical illustrations to depict mortality rates and show how improvements in sanitary conditions would lead would lead to decrease in deaths. By focusing on health and disease trends among populations. Ms. Nightingale saved or improved the lives of countless individuals, the ultimate goal of epidemiology.

Definition of related concept An epidemic refers to a disease occurrence that clearly exceeds the normal or expected frequency in a community or region. Epidemics: infections affecting a large number of people at the same time. - Examples: - In past centuries, epidemic of cholera, smallpox swept through community after community , killing thousands of people, changing the community structure.

Definition of related concept Pandemic: An epidemic that worldwide in distribution. - Pandemic: infections affecting extremely high numbers of people, usually in many countries. Examples: -Acquired Immunodeficiency Syndrome (AIDS) is worldwide in distribution.

Definition of related concept • Endemic: • The continuing presence of a disease or infectious agent in a given geographic area. • Examples: • Plague in Vietnam. • Malaria in the tropic of, Africa, Brazil and Indonesia.

Definition of related concept • Biostatistics: • Is the science of statically measuring population health condition. • - Biostatistics are the primary public health measurement and analytic science underlying community health practice. • - Biostatistics helps to describe the extent and distribution of health, illness, and conditions in the community. • - Biostatistics aids in the identification of specific health problems and community strengths. • - It facilitates the setting priorities for program planning.

Definition of related concept A few Statistics Rate, ratio, incidence, and prevalence are common terms used to help describe illness and disease among population groups. A rate: A statistical measures expressing the proportion of persons with a given health problem among a population at risk. Number of events A rate is= --------------------X100,000 Population at risk .

Definition of related concept • A ratio: • which is simply the comparison of one number with another. • A ratio: is often used to compare one at-risk population with another. • The number of females: The number of males • .

Definition of related concept • Mortality: Death rate. • Morbidity: Illness rate. • Mortality and morbidity statistics are collected routinely and used as indicators of the frequency of deaths and disease as they occur in time, place, and persons. • .

Definition of related concept • Incidenceand Prevalence Rates • Incidence: Refers to the rate at which a specific disease develops in a population. • An incidence rate is the number of new cases of an illness or injury that occurs in a specific time. • Number of persons developing a disease • Incidence rate=------------------------------------- X 100,000 • Total number at risk per unit of time.

Definition of related concept • Prevalence: measures all of the existing cases at a • given point of time. • Prevalence includes the incidence (new cases) plus all of the existing cases. • The prevalence rate is influenced by how many people become ill, and by the number of people who die, or do not recover. • Number of persons developing a disease • Prevalence rate= ---------------------------------X100,000 • Total number at risk per unit of time

CONCEPTS BASIC TO EPIDEMIOLOGY CONCEPTS BASIC TO EPIDEMIOLOGY The science of epidemiology draws on certain basic concepts and principles to analyze and understand patterns of occurrence among aggregate health conditions.

CONCEPTS BASIC TO EPIDEMIOLOGY I. Host, Agent, and Environment Model Host, Agent, and Environment Model Through their early study of infectious diseases, epidemiologists began to consider disease states generally in terms of the epidemiologic triad, or the host, agent, and environment model. Interactions among these three elements explained infectious and other disease patterns.

Host, Agent, and Environment Model …. cont • The host is a susceptible human or animal who harbors and nourishes a disease-causing agent. • Many physical, psychological, and lifestyle factors influence the host’s susceptibility and response to an agent. • Physical factors include age, sex, race, and genetic influences on the host’s vulnerability or resistance. • Psychological factors, such as outlook and response to stress, can strongly influence host susceptibility. • Lifestyle factors also play a major role. Diet, exercise, sleep patterns, and healthy or unhealthy habits all contribute to either increased or decreased vulnerability to the disease-causing agent..

Host, Agent, and Environment Model …. cont • Agent is a factor that causes or contributes to a health problem or condition. • Causative agents can be factors that are present (eg, bacteria that cause tuberculosis, rocks on a mountain road that contribute to an automobile crash) or factors that are lacking (eg, lack of iron in the body that causes anemia; lack of seat belt use that contributes to the extent of injury during an automobile crash). • Agents vary considerably and include five types: biologic, chemical, nutrient, physical, and psychological. Biologic agents include bacteria, viruses, fungi, protozoa, worms, and insects.

Host, Agent, and Environment Model …. cont • The environment refers to all the external factors surrounding the host that might influence vulnerability or resistance. • The physical environment includes factors such as geography, climate, weather, safety of buildings, water and food supply, and presence of animals, plants, insects, and microorganisms that have the capacity to serve as reservoirs (storage sites for disease-causing agents) or vectors (carriers) for transmitting disease. • The psychosocial environment refers to social, cultural, economic, and psychological influences and conditions that affect health, such as access to health care, cultural health practices, poverty, and work stressors, which can all contribute to disease or health.

Host, Agent, and Environment Model …. cont • Host, agent, and environment interact to cause a disease or health condition. • For example, the agent responsible for Lyme disease is the spirochete Borreliaburgdorferi; • humans of all ages are susceptible hosts, along with dogs, cattle, and horses. Ticks that feed on wild rodents and deer transfer the spirochete to human hosts after feeding on them for several hours. • Environmental factors, such as working or playing in tick-infested areas, influence host vulnerability.

CONCEPTS BASIC TO EPIDEMIOLOGY II. Causality Causality refers to the relationship between a cause and its effect. A purpose of epidemiologic study has been to discover causal relationships, so as to understand why conditions develop and offer effective prevention and protection. Over the years, however, as scientific knowledge of health and disease has expanded, epidemiology has changed its view of causality

CONCEPTS BASIC TO EPIDEMIOLOGY III. Immunity Immunity refers to a host’s ability to resist a particular infectious disease–causing agent. This occurs when the body forms antibodies and lymphocytes that react with the foreign antigenic molecules and render them harmless. For community health nursing, this concept has significance in determining which individuals and groups are protected against disease and which may be vulnerable. Four types of immunity are important in community health: passive immunity, active immunity, cross-immunity, and herd immunity.

Immunity 1. Passive immunity refers to short-term resistance that is acquired either naturally or artificially. Newborns, through maternal antibody transfer, have natural passive immunity that lasts about 6 months. Artificial passive immunity is attained through inoculation with a vaccine that gives temporary resistance.

Immunity 2. Active immunity is long-term and sometimes lifelong resistance that is acquired either naturally or artificially. Naturally acquired active immunity comes through host infection.. Artificially acquired active immunity is attained through vaccine inoculation. Such vaccines are prepared from killed, living-attenuated, or living-virulent organisms administered to artificially produce or increase immunity to a particular disease.

Immunity 3. Cross-immunity refers to a situation in which a person’s immunity to one agent provides immunity to another related agent as well. The immunity can be either passive or active. Sometimes, infection with one disease, such as cowpox, gives immunity to a related disease, such as smallpox..

Immunity 4. Herd immunity describes the immunity level that is present in a population group (Chin, 1999). A population with low herd immunity is one with few immune members; consequently, it is more susceptible to the disease. Nonimmune people are more likely to contract the disease and spread it throughout the group, placing the entire population at greater risk...

CONCEPTS BASIC TO EPIDEMIOLOGY • Risk • To determine the chances that a disease or health problem will occur, epidemiologists are concerned with risk, or the probability that a disease or other unfavorable health condition will develop. • For any given group of people, the risk of developing a health problem is directly influenced by their biology, environment, lifestyle, and system of health care

Risk … cont A population at risk is a collection of people among whom a health problem has the possibility of developing because certain influencing factors are present (eg, exposure to HIV) or absent (eg, lack of childhood immunizations, lack of specific vitamins in the diet), or because there are modifiable risk factors (eg, with cardiovascular disease). Incidence in exposed group Relative risk ratio = ------------------------------ Incidence in unexposed group

Sources of information for epidemiological study • SOURCES OF INFORMATION • Epidemiologic investigators may draw data from any of three major sources: • existing data, • informal investigations, • (3) scientific studies. • The community health nurse will find all three sources useful in efforts to improve the health of aggregates.

Existing Data 1) Existing Data A variety of information is available nationally, by state, and by section, such as county, region, or urbanized area. This information a. Vital Statistics Vital statistics refers to the information gathered from ongoing registration of births, deaths, adoptions, divorces, and marriages. Certification of births, deaths, and fetal deaths are the most useful vital statistics in epidemiologic studies Sources for vital statistical information include state Web sites on the Internet, local and state health departments, city halls, and county halls of records

Existing Data b. Census Data Data from population censuses taken every 10 years in many countries are the main source of population statistics. This information can be a valuable assessment tool for the community health nurse who is taking part in health planning for aggregates. Population statistics can be analyzed by age, sex, race, ethnic background, type of occupation, income gradient, marital status, educational level, or other standards, such as housing quality. Analysis of population statistics can provide the community health nurse with a better understanding of the community and help identify specific areas that may warrant further epidemiologic investigation. Data from the KSA. Census Bureau is found on their Web site.

Existing Data c. Reportable Diseases Each state has developed laws or regulations that require health organizations and practitioners to report to their local health authority cases of certain communicable and infectious diseases that can be spread through the community. This reporting enables the health department to take the most appropriate and efficient action. All states require that diseases subject to international quarantine regulations be reported immediately.

Existing Data d. Disease Registries Some areas or states have disease registries or rosters for conditions with major public health impact. Tuberculosis and rheumatic fever registries were more common when these diseases occurred more frequently. Cancer registries provide useful incidence, prevalence, and survival data and assist the community health nurse in monitoring cancer patterns within a community. Community health nurses can access these registries through state health department Web sites.

Existing Data e. Environmental Monitoring State governments, through health departments or other agencies, now monitor health hazards found in the environment. Pesticides, industrial wastes, radioactive or nuclear materials, chemical additives in foods, and medicinal drugs have joined the list of pollutants Concerned community members and leaders view these as risk factors that affect health at both community and individual levels. Community health nurses can also obtain data from federal agencies such as the Food and Drug Administration, the Consumer Product Safety Commission, and the Environmental Protection Agency.

Sources of information for epidemiological study 2) Informal Observational Studies A second information source in epidemiologic study is informal observation and description. Almost any client group encountered by the community health nurse can trigger such a study. 3) Scientific Studies The third source of information used in epidemiologic inquiry involves carefully designed scientific studies. The nursing profession has recognized the need to develop a systematic body of knowledge on which to base nursing practice. Already, systematic research is becoming an accepted part of the community health nurse’s role. Findings from epidemiologic studies conducted by or involving nurses are appearing more frequently in the literature

Method in the epidemiologic investigation process METHODS IN THE EPIDEMIOLOGIC The goals of epidemiologic investigation are to identify the causal mechanisms of health and illness states and to develop measures for preventing illness and promoting health. Epidemiologists employ an investigative process that involves a sequence of three approaches that build on one another: descriptive, analytic, and experimental studies. All three approaches have relevance for community health nursing

Method in the epidemiologic investigation process Descriptive Epidemiology includes investigations that seek to observe and describe patterns of health-related conditions that occur naturally in a population. example, a community health nurse might seek to learn how many children in a school district have been immunized for measles, how many home births occur each year in the county, how many cases of STDs have occurred in the city in the past month, or how many automobile crashes have occurred near the community high school. At this stage in the epidemiologic investigation, the researcher seeks to establish the occurrence of a problem. Data from descriptive studies suggest hypotheses for further testing. Descriptive studies almost always involve some form of broad-based quantification and statistical analysis.

Method in the epidemiologic investigation process • Descriptive Epidemiology • Counts • Rates • a. incidence rate • b. prevalence rate • c. period prevalence rate • Crude Mortality Rate • Cause-Specific Mortality Rate • Case Fatality Rate • Proportional Mortality Ratio • Age-Specific Mortality Rate • 3. Computing Rates • 3:1 mortality rate • 3:2 morbidity rate

Method in the epidemiologic investigation process • Analytic Epidemiology • A second type of investigation, analytic epidemiology, goes beyond simple description or observation and seeks to identify associations between a particular human disease or health problem and its possible causes. Analytic studies tend to be more specific than descriptive studies in their focus • Prevalence Studies • Case-Control Studies • Cohort Studies

Method in the epidemiologic investigation process Experimental Epidemiology Experimental epidemiology follows and builds on information gathered from descriptive and analytic approaches. It is used to study epidemics, the etiology of human disease, the value of preventive and therapeutic measures, and the evaluation of health services (Valanis, 1999). In an experimental study, the investigator actually controls or changes the factors suspected of causing the health condition under study and observes what happens to the health state. In human populations, experimental studies should focus on disease prevention or health promotion rather than testing the causes of disease, which is done primarily on animals.

Epidemiology in Community Health Care