Epidemiology in Community Health Care PDF

Epidemiology in community health care Historical Roots of Epidemiology Ancient Times: Hippocrates (460 to 375 BCE) Middle Ages: 1348—Plague (Black Death) 18th century: Florence Nightingale (1820 to 1910) 19th century: Modern epidemiology Causal thinking Sa...

Epidemiology in community health care Historical Roots of Epidemiology Ancient Times: Hippocrates (460 to 375 BCE) Middle Ages: 1348—Plague (Black Death) 18th century: Florence Nightingale (1820 to 1910) 19th century: Modern epidemiology Causal thinking Sanitary statistics Infectious-disease epidemiology Chronic-disease epidemiology Current: Eco-epidemiology Classically speaking Epi = upon Demos = people Ology = science Epidemiology = the science which deals with what falls upon people….. Bridge between biomedical, social and behavioral sciences A Modern Definition Study of the occurrence and distribution of health- related diseases or events in specified populations, including the study of the determinants influencing such states, and the application of this knowledge to control the health problem (Porta M, Last J, Greenland S. A Dictionary of Epidemiology, 2008)  Terms to know Disease a pattern of response by a living organism to some form of invasion by a foreign substance or injury which causes an alteration of the organisms normal functioning also – an abnormal state in which the body is not capable of responding to or carrying on its normally required functions Pathogens organisms or substances such as bacteria, viruses, or parasites that are capable of producing diseases Pathogenesis the development, production, or process of generating a disease Pathogenic means disease causing or producing Pathogenicity describes the potential ability and strength of a pathogenic substance to cause disease  Terms to know Etiology the factors contributing to the source of or causation of a disease Toxins a poisonous substance that is a specific product of the metabolic activities of a living organism and is usually very unstable notably toxic when introduced into the tissues, and typically capable of inducing antibody formation Antibiotics a substance produced by or a semisynthetic substance derived from a microorganism and able in dilute solution to inhibit or kill another microorganism  Terms to know incidence: the extent that people, within a population who do not have a disease, develop the disease during a specific time period prevalence: the number of people within a population who have a certain disease at a given point in time point prevalence: how many cases of a disease exist in a group of people at that moment. prevalence relies on 2 factors: How many people have had the disease in the past Duration of the disease in the population Immunity: The host` ability to resist a particular infectious disease-causing agent. Acquired immunity : is the resistance acquired by a host as a result of previous exposure to an infection. Nosocomial infection: in the episodic setting an infection that is not present or incubating at the time of admission (hospital infection). Herd immunity: describe the immunity level that is present in population group Theories of Causality in Health and Illness Relationship between a cause and its effect Chain of causation Causation in noninfectious disease: environmental exposure and potential health outcomes (nine elements) Multiple causation Dever’s epidemiological model also called the Web of Causation  Purposes of Epidemiology 1. To investigate nature / extent of health- related phenomena in the community / identify priorities 2. To study natural history and prognosis of health-related problems 3. To identify causes and risk factors 4. To recommend / assist in application of / evaluate best interventions (preventive and therapeutic measures) 5. To provide foundation for public policy  Uses of Epidemiology To study the cause (or etiology) of disease(s), or conditions, disorders, disabilities, etc. determine the primary agent responsible or ascertain causative factors determine the characteristics of the agent or causative factors define the mode of transmission determine contributing factors identify and determine geographic patterns To determine, describe, and report on the natural course of disease, disability, injury, and death. To aid in the planning and development of health services and programs To provide administrative and planning data  USES OF EPIDEMIOLOGY IN DISEASE CONTROL AND PREVENTION 1. Identifying characteristics of people who suffered from a disease such as cholera or plague and compared them with characteristics of those who are healthy such as personal factors, socioeconomic status and health status Questioning whether there were differences in the location or.2 living environment of ill people compared with healthy individuals and whether these factors influenced disease development Examining whether common time factors existed (i.e., when.3 people acquired disease) EPIDEMILOGICAL METHODS 1. Descriptive epidemiology : Descriptive Epidemiology focuses on the amount and distribution of health and health problems within a population. Its purpose is to describe the characteristics of people who are protected from disease and those who have a disease. Factors of particular interest include age, sex, ethnicity or race, socioeconomic status, occupation and family status. Epidemiologists use morbidity and mortality rates to describe the extent of disease and to determine the risk factors that make certain groups prone to acquiring disease. Basic Triad of Descriptive Epidemiology THE THREE ESSENTIAL CHARACTERISTICS OF DISEASE WE LOOK FOR IN DESCRIPTIVE EPIDEMIOLOGY ARE: PERSON PLACE TIME Personal Characteristics (whom) Age Gender Socio-economic status (education, occupation, income) Marital status Ethnicity/race/genetic profile Behavior / habits Place (where ?) Geographically restricted or widespread (outbreak, epidemic, pandemic)? Off-shore (tsunami…) Climate effects (temperature, humidity, combined effects..) Urban / sub-urban-squatter / rural Relation to environmental exposure (water, food supply, etc) Multiple clusters or one?  Time (when ?) Changing or stable? Clustered (epidemic) or evenly distributed (endemic)? Time-trends: Point source, propagated, seasonal, secular, combinations 2. Analytic Epidemiology: Analytic Epidemiology investigates the causes of disease by determining why a disease rate is lower in one population group than in another. This method tests hypothesis generated from descriptive data and either accepts or rejects them on the basis of analytic research. The epidemiologist seeks to establish a cause and effect relationship between preexisting condition or event and the disease. THE THREE PHENOMENA ASSESSED IN :ANALYTIC EPIDEMIOLOGY ARE Basic triad of analytical epidemiology HOST AGENT ENVIRONMENT  Agents Biological (micro-organisms) Physical (temperature, radiation, trauma, others) Chemical (acids, alkalis, poisons, tobacco, others) Environmental (nutrients in diet, allergens, others) Psychological experiences  Host Factors Genetic endowment Immunologic status Personal characteristics Personal behavior Definitive versus intermediate (in vector-borne diseases)  Environment Living conditions (housing, crowding, water supply, refuse, sewage, etc) Atmosphere / climate Modes of communication: phenomena in the environment that bring host and agent together, such as: vector, vehicle, reservoir, etc) Type of analytic Epidemiology Prevalence studies Case-control studies Cohort studies Experimental epidemiology Sources of Epidemiologic Information Vital statistics Census data Reportable diseases Disease registries Environmental monitoring National Center for Health Statistics Health surveys Informal observational studies Scientific studies  Disease Transmission Fomites: inanimate objects that serve as a role in disease transmission Pencils, pens, doorknobs, infected blankets Vector: any living non-human carrier of disease that transports and serves the process of disease transmission Insects: fly, flea, mosquito; rodents; deer Reservoirs: humans, animals, plants, soils or inanimate organic matter (feces or food) in which infectious organisms live and multiply Humans often serve as reservoir and host Zoonois: when a animal transmits a disease to a human Carrier: one that spreads or harbors an infectious organism Some carriers may be infected and not be sick. e.g. Typhoid Mary Mary Mallon (1869 – 1938) was the first person in the United States to be identified as a healthy carrier of typhoid fever. Over the course of her career as a cook, she infected 47 people, three of whom died from the disease. Her notoriety is in part due to her vehement denial of her own role in spreading the disease, together with her refusal to cease working as a cook. She was forcibly quarantined twice by public health authorities and died in quarantine. It is possible that she was born with the disease, as her mother had typhoid fever during her pregnancy.  Disease Transmission Active carrier: individual exposed to and harbors a disease- causing organism. May have recovered from the disease Convalescent carrier: exposed to and harbors disease-causing organism (pathogen) and is in the recovery phase but is still infectious Healthy carrier: exposed to an harbors pathogen, has not shown any symptoms Incubatory carrier: exposed to and harbors a disease and is in the beginning stages of the disease, showing symptoms, and has the ability to transmit the disease Intermittent carrier: exposed to and harbors disease and can intermittently spread the disease Passive carrier: exposed to and harbors disease causing organism, but has no signs or symptoms  Modes Disease Transmission Modes of disease transmission methods by which an agent can be passed from one host to the next or can exit the host to infect another susceptible host (either person or animal) Two general modes direct indirect Direct transmission or person to person Immediate transfer of the pathogen or agent Direct transmission or person to person Immediate transfer of the pathogen or agent from a host/reservoir to a susceptible host Can occur through direct physical contact or direct personal contact such as touching contaminated hands, kissing or sex Indirect transmission pathogens or agents are transferred or carried by some intermediate item or organism, means or process to a susceptible host done in one or more following ways: airborne, waterborne, vehicleborne, vectorborne  Modes Disease Transmission Indirect transmission Airborne Droplets or dust particles carry the pathogen to the host and infect it Sneezing, coughing, talking all spray microscopic droplets in the air Waterborne Carried in drinking water, swimming pool, streams or lakes used for swimming. Examples: cholera Vehicleborne Related to fomites Vectorborne A pathogen uses a host (fly, flea, louse, or rat) as a mechanism for a ride or nourishment this is mechanical transmission biological transmission when the pathogen undergoes changes as part of its life cycle, while within the host/vector and before being transmitted to the new host Diseases for which vaccines are used Antrhax Pneumonia Chicken pox Polio Cholera Rabies Diphtheria Small pox German measles (rubella) Spotted fever Hepatitis A & B Tetanus Influenza Malaria (in process) Tuberculosis Measles Typhoid Fever Menigitis Typhus Mumps Whooping Cough Plague Yellow Fever Risk Probability that a disease or unfavorable health condition will develop Directly influenced by biology, environment, lifestyle, and system of health care Risk factors: negative influences Epidemiologists studying populations at risk: collection of people among whom a health problem has the possibility of developing because certain influencing factors are present or absent or because there are modifiable risk factors Measurement of relative risk ratio: incidence rate in exposed group/incidence rate in unexposed group RISK FACTORS Risk factors variables that increase the rate of disease in people who have them (e.g., a genetic predisposition) or in those exposed to them (e.g., an infectious agent or a diet high in saturated fat). Therefore their identification is critical to identifying specific prevention and intervention approaches that effectively and efficiently reduces chronic disease morbidity and mortality. For example, the identification of cardiovascular disease risk factors has suggested a number of lifestyle modifications that could reduce the morbidity risk before disease onset. Primary prevention strategies such as dietary saturated fat reduction, smoking cessation and hypertension control developed in response to previous epidemiological studies that identified these risk factors. Risk Estimates Risk, also known as cumulative incidence, has a similar meaning in epidemiology as it does in everyday usage – it is about chance. Risk is the probability that a negative event will occur. In epidemiology, risk is the observed or calculated probability that a health event will occur in a known population - within a specified time frame after exposure to a specific hazard. 200 people - the study population - go for a 2-hour walk in the snow wearing light clothes (the risk factor). After the walk, 10 people develop a cold. The risk - the number of new cases that occurred during the study - of developing a cold after walking in the snow with light clothes is therefore 5%. 32 The risk rate is 10 cases per 2 hours. Risk Rate The risk rate (or incidence rate) introduces the notion of time. Risk rates also measure the frequency of new cases of a health event in a population, but they take into account the sum of time that each participant remained under observation and at risk of developing the health event under investigation. The risk rate is the frequency with which new health events occur in a particular time frame - the number of new cases in a time period. Everyone walked the same amount of time, 2 hours, in the snow. They were all exposed to the risk factor for the same amount of time. In real life things are different. Everyone is exposed to risk factors for different amounts of time. Epidemiology provides a solution by considering every individual’s exposure time and summing it all up to build a ‘total exposure time’ for the cohort - the group of people being studied. 33 Relative Risk Relative risk measures reflect the increase in frequency of the health event in one population versus another..The unexposed population is treated as the baseline Relative risk measures the strength of an association between exposure and disease and whether an observed association is likely to be causal. 34 Methods in Epidemiologic Investigative Process Descriptive epidemiology Counts Rates Incidence: refers to all new cases of a disease or health condition appearing during a given time Number of persons developing a disease Total number at risk per unit of time Methods in Epidemiologic Investigative Process (cont.) Rates (cont.) Prevalence: all of the people with a particular health condition existing in a given population at a given point in time Number of persons with a characteristic Total number in population Computing rates Mortality Morbidity RATES: Rates are statistical measures expressing the proportion of people with a given health problem among population. When raw counts are converted to rates, the community health nurse can make meaningful comparisons with rates from other countries, from the nation and from previous time periods. These analyses assist the nurse in determining the magnitude of a public health problem in a given area and allow more reliable tracking of trends in the community over time Specific Rates for Maternal and Infant Populations Crude Birth Rate = Number of Live Births During 1 Year Estimated Population as of July 1 of Same Year × 1,000 General Fertility Rate = Number of Live Births During 1 Year Number of Females Aged 15-44 as of July 1 of Same Year × 1,000 Maternal Mortality Rate = Number of Deaths From Pueperal Causes During 1 Year Number of Live Births During Same Year ×100,000 Infant Mortality Rate = Number of Deaths Under 1 Year of Age for Given Year Number of Live Births Reported for Same Year × 1,000 Perinatal Mortality Rate = Number of Fetal Deaths Plus Infant Deaths Under 7 Days of Age During 1 Year Number of Live Births Plus Fetal Deaths During Same Year × 1,000 Epidemiologic research includes seven steps 1. Identify the problem, which is usually a threat to the population’s health. 2. 2. review the literature to determine what other studies have found. 3. Carefully design the study. 4. Collect the data. 5. analyze the findings. 6. Develop conclusions and applications. 7. Disseminate the findings. Aggregate Health 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. Wellness models that at first focused on individual behavior now include approaches that encompass aggregates. USE OF EPIDEMIOLOGY IN DISEASE PREVENTION 1. Primary Prevention The central goals of epidemiology are: a. Describing the disease patterns b. Identifying the etiologic factors in disease development c. Finding the most effective preventive measures. When these measures occur before disease development, they are called primary prevention. Primary prevention relies on epidemiological information to indicate those behaviors that are protective, or will not contribute to an increase in disease, and those that are associated with increased risk. 2. Secondary and Tertiary Prevention Secondary prevention occurs after pathogenesis. Those measures designed to detect disease at its earliest stage, namely screening and physical examinations that are aimed at early diagnosis, are secondary prevention. Interventions that provide for early treatment and cure of disease are also in this category. Tertiary prevention includes the limitation of disability and the rehabilitation of those with irreversible disease such as diabetes and spinal cord injury. ESTABLISHING CAUSALITY The criteria can be used with infectious disease, yet their significance lies with attributing cause in noninfectious disease. Each of the nine elements is summarized below :  1. Strength of association: This refers to the ratio of disease rates in those with and without the suspected causal factor. A strong association would be noted if disease rates are much higher in the group with the factor than in the group without it. 2. Consistency: An association is demonstrated in varying types of studies among diverse study groups (i.e., replication). 3. Specificity: A cause leads to one effect (not always the case in noninfectious diseases). 4. Temporality: Exposure to the suspected factor must precede the onset of disease (i.e., time order or time sequence).  5. Biological gradient: This relationship is demonstrated if, with increasing levels of exposure to the factor, there is a corresponding increase in occurrence of the disease (i.e., dose–response relationship). 6. Plausibility: The hypothesized cause makes sense based on current biologic or social models (i.e., it is possible). 7. Coherence of explanation: The hypothesized cause makes sense based on current knowledge about the natural history or biology of the disease (i.e., scientific knowledge).  8. Experiment: Experimental and nonexperimental studies support the association (e.g., reduced tobacco use in a population should lead to reduced lung cancer rates). 9. Analogy: Similarities between the association of interest and others (e.g., potential links to birth defects from new drugs is a concern since we already recognize this potential from the use of the drug thalidomide during the 1950s and early 1960s). Question Is the following statement true or false? The current thinking of epidemiology focuses on causal thinking. Answer False Rationale: Current thinking of epidemiology is termed eco-epidemiology, distinguished by transforming global health patterns and technological advances. Question Is the following statement true or false? Analytic epidemiology involves cohort studies. Answer True Rationale: Analytic epidemiology attempts to identify associations between a human disease or health problem and its possible causes. Analytic studies include prevalence studies, case–control studies, and cohort studies.