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Public Health PUBH 600 3: Principles and
Practice of Epidemiology Final Study Guide
Who is Imhotep ( 2650 - 2600 BC)? - ✔✔Egyptian founder of medicine. Diagnosed and treated over 200 diseases, performed surgery, and practiced some dentistry. He extracted medicine from plants. Was also a master architect and credited as the builder of the first pyramid at Saqqara. Who was Hippocrates ( 460 - 377 BC)? - ✔✔Was regarded as the "Father of Medicine", until evidence on the contributions of Imhotep surfaced. Wrote "On Airs, Waters, and Places" which made many observations about environmental and behavioral causes of disease. Who was Girolamo Fracastoro ( 1478 - 1553 )? - ✔✔Italian physician and poet. Wrote "De Contagione et contagiosis morbis", a treatise on the concept of contagious disease and infection. He also coined the term 'syphilis'. He proposed a scientific germ theory of disease 300 years before its empirical formulation by Louis Pasteur and Robert Koch. Who was John Graunt ( 1630 - 1674 )? - ✔✔Haberdasher and demographer. Developed statistical and census methods. Developed first life table. Analyzed mortality in London to study onset and spread of the plague. Who was Bernadino Ramazzini ( 1633 - 1714 )? - ✔✔Professor of Medicine in Modena, Italy. Wrote a book entitled ?The Diseases of Workers? (De Morbis Artificium Diatriba) that became influential in the area of occupational medicine and health. First to observe that disease among workers arose from harmful exposures encountered in the workplace. He was also 1 st to observe higher rates of breast cancer
Who was Edward Jenner (1 749 - 1823 )? - ✔✔Edward Jenner ( 1749 - 1823 ): English surgeon. Observed persons infected with cowpox appeared to be protected against smallpox. In 1768 , administered cowpox material to 8 - year old boy. Later, he exposed the boy to smallpox. First 'vaccine trial'. Who was James Lind ( 1716 - 1794 )? - ✔✔English surgeon. Conducted first clinical trials in 1747 among British sailors to examine effects of fresh fruits on preventing scurvy (before we knew of the concept of vitamins and vitamin deficiency) Who was William Farr ( 1807 - 1883 )? - ✔✔English physician. A contemporary of John Snow. Worked for the General Register Office. Responsible for collecting official medical statistics for England and Wales. Set up a system for routinely recording causes of death which played an essential role in Snow's investigations of cholera mortality. Who was John Snow ( 1813 - 1858 )? - ✔✔British Physician. Queen Victoria's anesthesiologist for the birth of her 8 th child. Called the 'Father of Modern Epidemiology' for his work on several cholera outbreaks in London. Identified the means of transmission decades before the discovery of the cholera vibrio. Who was Ignaz Semmelweis ( 1818 - 1865 )? - ✔✔Hungarian physician. Called the 'savior of mothers' for his seminal work on reducing the rate of puerperal fever by hand washing and sanitary practices. Resulted in a reduction of the rate of this often fatal disease (childbed fever) among mothers 10 - fold. Conducted systematic studies to verify this. Who was Florence Nightingale ( 1820 - 1910 )? - ✔✔Pioneer of profession of nursing. Made several contributions to the field of epidemiology. Was an excellent statistician and a great influence on the British Army Sanitary Commission. Was an expert in the visual and graphical depiction of data. First elected female member of the Royal Statistical Society.
Predicting disease occurrence, impact, and distribution in a community Estimating an individual's chance of suffering from diseases (risk) Evaluating preventive, therapeutic, and intervention activities Measuring the efficacy of health measures Studying historical disease trends Identifying disease syndromes Planning for current health needs Predicting future health care needs Provides the evidence base for establishing and evaluating public health policy What is primary prevention? - ✔✔Actions taken to prevent the development of disease among persons who do not have the disease What is secondary prevention? - ✔✔Actions taken among people who have already developed a disease to improve their prognosis; refers to early detection (screening) and early intervention What is tertiary prevention? - ✔✔Tertiary Prevention - Consists of the prevention of disease progression and suffering after a disease is clinically obvious and a diagnosis has been established.
Examples include routine screening for and management of early renal, eye and foot problems among diabetics. Often called "disease management." What is the natural progression in epidemiologic reasoning? - ✔✔ 1 st - Suspicion that a factor influences disease occurrence. Arises from clinical practice, lab research, examining disease patterns by person, place and time, prior epidemiologic studies 2 nd - Formulation of a specific hypothesis 3 rd - Conduct epidemiologic study to determine the relationship between the exposure and the disease. Need to consider chance, bias, confounding when interpreting the study results. 4 th - Judge whether association may be causal. Need to consider other research, strength of association, temporal aspects, etc. What is the epidemiologic triad? - ✔✔Host, vector, environment, agent Disease described as result of interaction between: a.) Susceptible host b.) Appropriate agent c.) Appropriate environment d.) Ability of agent to affect the host e.) Biologic/social host characteristics Model initially developed for infectious diseases but can apply to all diseases/conditions What are some agents of disease? - ✔✔Infectious organisms (note that some infectious agents require transmission by vectors)
Disease is related to environmental and personal characteristics that vary by: a.) Person b.) Place c.) Time Goal of descriptive epidemiology is to determine the groups who are most at risk (and ultimately, why) Characteristics of 'place' in epidemiology... - ✔✔Geographic differences may result from differences in: a.) Inhabitants b.) Environment c.) Data Quality We can examine geographic differences by comparing: a.) Spot Maps b.) Politically-Defined Areas c.) Naturally-Defined Areas d.) Migrant Studies What is a secular trend? - ✔✔A change in disease frequency occurring over a long period of time (years or decades) What is a cyclic change? - ✔✔Recurrent alterations in the frequency of disease (often seasonal) What are the 10 great public health achievements from 2001 - 2010 (U.S.)? - ✔✔Vaccine-Preventable Diseases
Prevention and Control of Infectious Diseases Tobacco Control Maternal and Infant Health Motor Vehicle Safety Cardiovascular Disease Prevention Occupational Safety Cancer Prevention Childhood Lead Poisoning Public Health Preparedness and Response What are the 10 great public health achievements world wide from 2001 - 2010? - ✔✔Reductions in Childhood Mortality Vaccine-Preventable Diseases Assess to Safe Water and Sanitation Malaria Prevention and Control Prevention and Control of HIV/AIDS
How is cholera transmitted? - ✔✔Cholera is transmitted by the fecal-oral route through contaminated water & food. Person to person infection is rare. The infectious dose of bacteria required to cause clinical disease varies with the source. If ingested with water the dose is in the order of 10 ^ 3 - 10 ^ 6 organisms. When ingested with food, fewer organisms are required to produce disease, namely 10 ^ 2 - 10 ^ 4. Cholera in children... - ✔✔Breast-fed infants are protected. Symptoms are severe & fever is frequent. Shock, drowsiness & coma are common. Hypoglycemia is a recognized complication, which may lead to convulsions. Rotavirus infection may give similar picture & need to be excluded. How is cholera treated? - ✔✔The primary goal of therapy is to replenish fluid losses caused by diarrhea & vomiting. Fluid therapy is accomplished in 2 phases: rehydration and maintenance. Rehydration should be completed in 4 hours & maintenance fluids should replace ongoing losses & provide daily requirement. John Snow and cholera... - ✔✔Cholera first appeared in England in 1 831
Believe to be spread by the "miasma theory" Four outbreaks between 1831 and 1854 Over 60 , 000 deaths In the mid- 19 th century, Soho was an unsanitary place of cow-sheds, slaughterhouses, and primitive, decaying sewers, and open cesspools. Initially, the worst-hit areas of London were Southwark and Lambeth On the night of August 31 , 1854 , ?the most terrible outbreak of cholera which ever occurred in the kingdom? broke out in Golden Square, Soho. During the next 3 days, 127 persons living in or around Broad Street died By September 10 , the number of deaths had reached 500 and the death rate for St. Anne's, Berwick Street and the Golden Square subdivisions of the parish had risen to 12. 5 %, more than double that for the rest of London. What is a population? - ✔✔Group of people with a common characteristic like age, race, sex, place of residence, religion, or use of hospital services. What is a fixed population? - ✔✔Membership is permanent and defined by an event Ex. Members of the Framingham Cohort; residents exposed to radiation from Chernobyl What is a dynamic population? - ✔✔Membership is transient and defined by being in or out of a "state"
b.) Maternal Mortality Ratio = # maternal deaths/1, 000 live births c.) Body Mass Index (BMI) = weight (kg) /height (m)^ What is a proportion? - ✔✔a/(a + b) Numerator included in the denominator Usually expressed as a percent (%) Range from 0 to 1 (or 0 % to 100 %) Examples a.) Proportion of males in the population: b.) Case fatality: c.) Cumulative incidence d.) Prevalence (rate) e.) Attack (rate) f.) Case-fatality (rate) (NOTE: these are not true rates) What is prevalence? - ✔✔Quantifies number of existing cases of disease in a population at a point or during a period of P = (Number of existing cases of disease)/(Number in total population) Ex. City A has 7000 people with arthritis on Jan 1 st, 1999 a.) Population of City A = 70 , 000 b.) Prevalence of arthritis on Jan 1 st =. 10 or 10 %
What is incidence? - ✔✔Quantifies number of new cases of disease that develop in a population at risk during a specified time period. New disease events, or for diseases that can occur more than once, usually first occurrence of disease Population at risk (candidate population) - can't have disease already Time must pass for a person to move from health to disease What is cumulative incidence? - ✔✔(Number of new cases of disease)/(Number in candidate population over a specified period of time) Cumulative incidence estimates the probability or risk that a person will develop disease DURING A SPECIFIED TIME PERIOD. Note that the candidate population is comprised of people who are "at risk" of getting the disease What is an incidence rate (IR)? - ✔✔(# new cases of disease)/(person-time of observation in candidate population) This measure is a true rate because it directly integrates time into the denominator. This is also called "Incidence Density"
Note: Only pop'n aged 25 - 34 is in the denominator. If a group can't be included in the numerator, it can't be included in the denominator either! What is a cause-specific mortality rate? - ✔✔(# deaths from a specific cause)/(total population) x 1000 What is a cause-specific death rate? - ✔✔Cause-Specific Death Rate due to Unintentional Injury per 100 , 000 U.S. ( 2000 ) ( 97 , 900 deaths due to unintentional injury)/( 275 , 265 , 000 U.S. pop'n) x 100 , 000 = 35 .6 deaths due to UI per 100 , 000 per year This is for all ages, it is not age-adjusted. What is case fatality? - ✔✔The proportion of people with a disease/diagnosis/condition/procedure, who die from it during a specified period of time after symptom onset/diagnosis/ treatment (etc.). Usually expressed as a percent. CF is a measure of disease severity. CF = (# deaths due to a specific disease)/(total # of persons with that disease) What is a crude-birth rate? - ✔✔(total number of livebirths for one year)/(total mid-year population) x 1000 (sometime defined as a rate per total # of women of childbearing age)
What is a neonatal mortality rate? - ✔✔(# deaths among children < 28 days of age)/(total # live births in same time period) What is an infant mortality rate? - ✔✔(# deaths of infants under 1 year of age for one year)/( 1 , 000 live- births) What is a fetal death ratio? - ✔✔(# fetal deaths during year)/(# live births in the same year) Fetal death defined as loss of fetus after 22 or more weeks of gestation (ACOG) What is an attack rate? - ✔✔(# cases of disease that develop during defined period)/(# in pop. at risk at start of period) Usually used for infectious disease outbreaks What is proportionate mortality? - ✔✔(# deaths from a specific cause)/(total number of deaths) x 100 How do we standardize rates? - ✔✔Difficult to interpret measures of comparison based on crude rates because groups may differ on important characteristics (age, gender, race) that can distort these measures. Standardization of rates minimizes these differences and provides an undistorted measure of comparison. What are the two methods of rate standardization? - ✔✔The DIRECT method of standardization The INDIRECT method of standardization.
RR= 2. 0 -- two times the risk of disease in the exposed compared to the unexposed RR = 0 .5 -- 0. 5 times or 1 / 2 the risk of disease in exposed compared to unexposed. What is risk/rate difference (absolute risk/rate)? - ✔✔RD=Rate or risk in exposed (R^exp) - Rate or risk in unexposed (R^unexp) For CI: CI^exp - CI^unexp = (a/ (a+b)) - (c/(c+d)) For IR: IR^exp - IR^unexp = (a/ PT^exp) - (c/PT^unexp) RD = 0 when there is no association the absolute effect of exposure on disease occurrence. The excess disease risk in the exposed group compared to the unexposed group. The public health impact of an exposure, that is, how much disease would be prevented if the exposure were removed. This assumes that the exposure causes the disease. What is population risk/rate difference (PRD)? - ✔✔Measures excess disease occurrence among the total population that is associated with the exposure. Helps to evaluate which exposures are most relevant to the health of a target population. Two formulas for PRD: a.) PRD = (RD) (P^exp) i.) Where P^exp = proportion of population that is exposed, and RD is the risk or rate difference
b.) PRD = R^total - R^unexp i.) Where R^total = risk/rate in total population and R^unexp = risk/rate among unexposed Who was Samuel Johnson? - ✔✔( 18 September 1709? 13 December 1784 ) Often referred to as Dr Johnson, was an English author who made lasting contributions to English literature as a poet, essayist, moralist, literary critic, biographer, editor and lexicographer. Johnson has been described as "arguably the most distinguished man of letters in English history". He is also the subject of "the most famous single work of biographical art in the whole of literature": James Boswell's Life of Samuel Johnson. After nine years of work, Johnson's A Dictionary of the English Language was published in 1 755 ; it had a far-reaching effect on Modern English and has been described as "one of the greatest single achievements of scholarship." This work brought Johnson popularity and success. Until the completion of the Oxford English Dictionary 150 years later, Johnson's was viewed as the pre-eminent British dictionary Why do epidemiologists use public data sets? - ✔✔Use of pre-existing data can allow a study to be done more cheaply, more quickly, and often on a larger scale than if new data collection were required. Most epidemiologic studies involve the use of rates Interpreting Rates and Trends a.) Need to assess whether observed differences in rates either within a country or when comparing countries are real or if they are artifactual dues to errors and biases in the way the data were collected. What are real reasons for differences in rates or trends? - ✔✔Changes in rates of disease due to changes (increases or decreases) in behavior; eg, smoking and lung cancer rates; NTD's and folic acid consumption Differences between populations in relevant demographic characteristics (SES, ethnic/racial) associated with environmental or behavioral risk
