question

Frequency measures are used to

answer

describe nominal (categorized/labeled) data

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many epidemiological nominal variables have ? categories

answer

two; alive/dead, case/control, exposed/not exposed dichotomous variables

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used with dichotomous variables are

answer

ratios, proportions, rates

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frequency measures are based on single formula

answer

(x/y)(10^n)

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what are being compared in frequency measures

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x and y quantities

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n'th power of 10 examples

answer

10^0=1 10^1=10 10^2=100 10^3=1000

question

ratio

answer

x and y may be independent from each other OR x may be included in y independent: females/males xy inclusive: females/total population

question

proportion

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is a ratio where x is included in y

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EMS Eosinophilia Myalgia Syndrome

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increase in eosinophils with severe muscle pain (chest/abdomen)

question

eosinophils

answer

type of WBC that attacks worms/toxins

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EMS has been associated with

answer

ingestions of contaminated L-tryptophan -amino acid isomer (health food sleep aid) -1988 Jap Co created genetically modified bacteria to make L tryptophan but strain also caused unidentified impurity -37 died, 1500 disabled

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Rate

answer

is a ratio, that measures the frequency/occurrence of an event over time

question

rate formula

answer

(number of cases or events in a given time/population at risk in a given time)(10^n)

question

rate formula requires (3)

answer

-cases must be from population in denominator (can be thought of as proportion) -numerator and denominator must occur in same time period -denominator pop must be at risk, must have at least the possibility of experiencing the event

question

ratios, proportions, and rates are used to describe 3 epidemiological events

answer

-morbidity -mortality -natality

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Morbidity Frequency Measures

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used to describe the presence/probability (risk) of disease in a populaiton

question

disease

answer

illness, injury, or disability

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Incidence rates

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**most common way to measure frequency of disease in a population -measures risk and is used to compare risks between different poulation

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what are rates better than for comparing disease occurrence and why

answer

better than raw numbers; because rates adjust data for population size

question

Incidence rate formula

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(new cases in a given time/population at risk in a given time)(10^n)

question

incidence rate example

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(50/100) high risk relative to (10/1000)

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incidence rate numerator

answer

-numerator only includes new cases in a given time

question

incidence rate denominator

answer

-population at risk should have possibility of developing disease (susceptible); difficult to eliminate non-susceptible in a large population, US census figures normally used; only in small population can non-susceptible be eliminated i.e. nursing homes, school, hospital -denominator pop must originate the numerator cases pop usually defined Geo-politically (state, county, city); pop may be defined by common experience (radiation exposure, eating at restaurant) -appropriate denominator is 1 out of 3 possibilities: pop size at start/time period, pop size at middle/time period, average size of pop over time period

question

incidence rate 10^n

answer

for nationally notifiable diseases (gonorrhea, HIV, plague) 10^n=10^5=100000 otherwise select 10^n where smallest rate calculated has a small whole number (use 4.2/100 not 0.42/10, 10^2 not 10^1) in all tables 10^n must be identified to inform reader

question

incidence rate implies

answer

change over time in health healthy-> disease state (new cases)

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incidence rate period of time

answer

must be specified (calendar year most common)

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Prevalence rate formula

answer

(new+preexisting cases in a given time/pop at risk in same given time) (10^n)

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Prevalence rate

answer

diff than incidence rate, includes all cases in numerator; may be point prevalence

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point prevalence

answer

amount of disease in an interval of time (week/mo/year)

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Prevalence VS Incidence

answer

prevalence includes ALL CASES (new+preexisiting in a give time) incidence includes (only new cases in a give time)

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chronic disease with unclear onset date is better described by (prevalence or incidence?)

answer

PREVALENCE! i.e. osteoarthritis, diabetes

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Factors increasing prevalence

answer

more duration of disease, prolonging life of disease, more incidence, immigration of cases, emigration of healthy, immigration of susceptible, better reporting of cases

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factors decreasing prevalence

answer

less duration, high fatality rate, less incidence (new cases), emigration of healthy, improved cure rate

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Attack rate

answer

type of incidence rate, applied to narrowly defined population for a limited time (epidemic) measures risk or probability of becoming a case if you are a contact of a primary case

question

attack rate (primary) formula

answer

(new cases in a given time/population at risk at beginning of time period)(100)

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attack rate expressed as a

answer

percent; 10^n is 10^2

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secondary attack rate formula

answer

(new cases among contacts of primary cases in a given time/total number of cases)(100)

question

secondary attack rate measures

answer

risk/probability of becoming a case if you are a contact of a primary case expressed as a percent

question

person-time rate

answer

type of incidence rate; used for cohort (follow-up) studies of disease with long incubation or latency periods ie AIDS cancer heart disease

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person-time rate formula

answer

(new cases in given time of observation/total observation time for all persons)(10^n)

question

person-time rate VS attack rate

answer

person-time rate takes into account persons lost to follow up, attack rate ignores attack rate better at finding the proportion of a population becoming ill in a short time period person-time rate=better to see how quickly people develop illness over extended time

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risk ratio (relative risk) formula

answer

(risk for group of primary interest/risk for comparison group) aka exposed over not

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risk ratio (relative risk)

answer

compares the health risk of a disease between two known well defined groups (cohorts)

question

Risk ratio (relative risk) characteristics

answer

-usually primary interest group is the exposed group and the comparison group is not exposed group -for diseases, incidence rate/attack rate are used as measure of risk for both groups-population at risk is known for these measures

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interpretation of risk ratio values

answer

if =1 both groups have identical risk if = >1 increased risk for primary group of interest the exposure may be causing the illness if = < 1 decreased risk for primary group of interest the exposure may have protective effect

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PELLAGRA

answer

deficiency of niacin (b vitamin, precursor of NAD coenzyme, helps enzyme function) in diet leads to 3D syndrome (dermatitis, diarrhea, dementia)

question

2x2 table showing attack rates (risk) of pellagra in males and females in 1920's

answer

females have greater risk than females; because not economically developed; exposed mill workers-risk was 0.2 very low; 1/5 of non mill workers (non exposed) numerator group appeared protected from risk compared to denominator group flour provides be vitamin

question

measure of association

answer

quantified relationship between exposure and disease for cohort studies; cohort studies may be historical

question

high risk ratio

answer

more likely exposure is causal for disease in question

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risk ratio of stroke for women (smoke vs not)

answer

smoke 49.6/don't 17.7 = 2.8:1

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risk ratio greater than 2 considered strong association between cause/effect

answer

increased risk ratio more likely cause effect

question

rate ratio

answer

used to compare rates of 2 groups; disease rate, death rate, person-time rate

question

rate ratio formula

answer

=(rate per primary interest group/rate per comparison group) =(exposed/non-exposed)

question

rate ratio interpretation

answer

similar to risk ratio (higher, more likely exposure is causal for disease in question)

question

in case control studies, we pick an arbitrary number of individuals for control group because

answer

we don't know the true size of population at risk

question

can't calculate incidence rate or attack rate so can't calculate relative risk

answer

can't do this without knowing size of population at risk.

question

odds ratio

answer

estimates relative risk by comparing exposure among cases to exposure among controls; is the measure of association used for case-control studies to quantify the relationship of exposure and disease

question

odds ratio is an indirect measure of

answer

risk

question

odds ratio formula

answer

(cases/exposure)(controls of not exposed)/(controls with exposure)*(cases of not exposed)

question

odds ratio compares

answer

odds (probability) of exposure, cases to controls

question

odds ratio: a/c , b/d aka cross product ratio

answer

a/c: odds of exposure among the cases b/d: odds of exposure among the controls odds ratio=(a/c) / (b/d) = (ad)/ (bc)

question

interpretation of odds ratio

answer

-if 1.0 odds of exposure are greater for cases (exposure is more likely associated with disease) indicates how likely exposure gave the disease agent to cases

question

odds ratio can be applied to historical cohort studies to approximate risk but is not a direct measure of risk as is the risk ratio

answer

1920s south Carolina pellagra study cases 2.5x more likely to be associated with exposure of being female than male by odds ratio but actual risk of illness by pellagra is 2.4x for females over males (risk ratio)

question

TWO MEASURES OF PUBLIC HEALTH IMPACT

answer

reflects burden on public that an exposed contributes to frequency of disease -attributable proportion -vaccine efficacy or effectiveness

question

attributable proportion (attributable risk %)

answer

the proportion of disease in an exposed group that is attributable to the exposure OR measusre the reduction of a disease if the exposure is reduced from the population

question

attributable proportion formula

answer

=(risk for exposed group - risk for unexposed group) / (risk for exposed group) all *100

question

vaccine efficacy or effectiveness

answer

proportionate reduction of disease in vaccinated group identified the amount of disease (%) reduced among those vaccinated

question

vaccine efficacy or effectiveness formula

answer

=(risk unvaccinated - risk vaccinated)/(risk unvaccined) *100

question

mortality frequency measures

answer

measures the frequency of death

question

mortality rate (generic formula)

answer

(deaths/given time)/(pop size/same time from which the deaths occurred) (10^n) *if based on vital statistics (death certificate) denominator=population at the middle of time period most 10n 10^3 or 10^5

question

crude mortality rate

answer

numerator deaths= due to all causes

question

age-specific mortality rate

answer

numerator deaths and denominator pop size form specific age group

question

cause-specific mortality rate

answer

numerator deaths due to specific cause

question

sex-specific mortality rate

answer

numerator deaths and denominator population size are limited to one sex M/F

question

race-specific mortality rate

answer

numerator deaths and denominator population size are limited to specific race

question

infant mortality rate formula

answer

deaths (<1yr old/given time)/(live births/same given time) * (10^3) deaths/1000 live births

question

infant mortality rate

answer

indicator of pop health, sensitive to socioeconomic and health care conditions greater IMR in less developed countries

question

IMR not exactly same as age specific death rate for infants because

answer

some infants may die in nation without being born there

question

neonatal mortality rate formula

answer

deaths (<28 days old/given time)/(live births/same given time) (10^3)

question

post neonatal mortality rate formula

answer

(deaths 28-364 DO/given time)/(live births/same given time)(10^3)

question

maternal mortality rate formula

answer

(deaths (pregnancy related)/given time)/(live births/given time) *10^5

question

maternal mortality rate

answer

expressed as deaths per 100000 live births; much less maternal death than infant death; numerator includes death while pregnant/within 42 days of pregnancy termination, but not accident-related death

question

death to case ratio formula

answer

(deaths due to a disease/given time)(new cases of disease in same time)(10n)

question

death to case ratio

answer

use when deaths in numerator are not necessarily restricted to new cases in denominator some deaths in numerator may be due to development of disease in a time period prior to the time period of new cases

question

death to case ratio example

answer

diphtheria caused by corynebacterium diphtheriae bacteria that infect the throat, cause a pseudo membrane (tough, fiber-like covering) which can block airways, may spread via bloodstream to heart; 10% fatality; vax good for 10 yrs; death to case ratio 7.83/100 some could be due to development disease so ratio not proportion

question

case fatality rate

answer

proportion (x included in y) of those with a disease that die from that disease deaths in numerator are restricted to cases in denominator

question

case-fatality rate formula

answer

(deaths among cases/given time)(cases of the disease/same time)(10n)

question

case fatality rate measures

answer

severity/virulence of disease; greater CFR, more virulent disease

question

case fatality rate example

answer

zaire virus (zaire ebola virus) causes hemorrhagic fever with case-fatality rate of up to 90% with an average case fatality rate of about 83% CDC reports Hep A virus in US has overall case-fatality rate of about 0.3% with 1.8 among >50 YO

question

proportionate mortality rate formula

answer

(deaths due to disease/given time)/(deaths due to all causes/same time)(100)

question

proportionate mortality rate

answer

expressed as %; proportion of deaths due to specific cause heart disease PMR-35%, now 28% but still #1 cause of death

question

PRIMARY CAUSES OF DEATH 1987 (6)

answer

heart disease, cancer, cerebrovascular disease, accidents, chronic pulmonary disease, pneumonia+influenza

question

PRIMARY CAUSES OF DEATH 2003 (6)

answer

heart disease, cancer, stroke, chronic lower respiratory, accidents, diabetes

question

diabetes

answer

fasting blood glucose of >126 mg/dL not enough insulin to signal cells to take up glucose or cell ignores insulin signal, high sugar hurts eyes, kidneys, nerves, heart assoc with obesity, lack of exercise, genetics type 1-juvenile, failure to produce insulin type 2- failure to produce/use insulin, most common type

question

proportionate mortality ratio formula

answer

(proportionate mortality/group of interest)/(proportionate mortality/entire population)

question

proportionate mortality ratio

answer

compare PM of group to PM of entire pop PMR greater than 1=cause of group mortality accounts for a greater proportion of deaths in population than expected

question

PMRatio ex

answer

rosenman Sanbury lung cancer in former workers with chromium compounds PCMR 1.51 white men 1.34 black men; lack of increase in other smoking related diseases suggest that lung cancer not related to smoking

question

YEARS of potential life lost

answer

measures premature mortality in relation to a predetermined endpoint usually 65.70.75 or average life expectancy any death prior to endpoint is considered premature; this mortality measure is weighted towards deaths at younger ages [death of 10 YO counts more than that of 50]

question

YPLL determined two ways

answer

YPLL from line listing data YPLL from frequency distribution data

question

YPLL from line listing data

answer

calculate each individual YPLL then sum for group =[sum(predetermined endpoint age - age of death before endpoint)] endpoint 65 death 45 YPLL 20

question

YPLL from frequency distribution data

answer

uses age group data -calculate midpoint for each age group [(age group youngest+oldest age+1)/(2)] ---(endpoint-midpoint of age group)*(deaths in age group)=age group YPLL

question

YPLL RATE formula

answer

(YPLL/pop under endpoint age)(10n)

question

YPLL rate

answer

used to compare YPLL between different populations

question

age adjusted mortality rate

answer

mortality rate increases with age, if mortality rates for 2+ pop are studied must assure mortality difference isn't due only to age diff in diff pop pop/more elderly has higher mortality rate to eliminate age diff adjust mortality rates of diff pop to a standard pop

question

direct method age adjusted death rate

answer

requires knowledge of age specific death rate

question

direct method age adjusted death rate procedure:

answer

age-specific death rate/100000* age group std pop=expected deaths for age group sum of all expected deaths for all age groups=total expected deaths total expected deaths *10^5/total standard population=age adjusted death rate for population

question

iNDIRECT METHOD FOR AGE ADJUSTED DEATH RATE

answer

USE IF LACK OF KNOWLEDGE OF AGE SPECIFIC DEATH RATE; SMALL POP CAN BE COMPARED TO LARGER GROUP

question

standardized mortality rate formula

answer

this is an indirect method of age-adjusted death rate (observed deaths/expected deaths)(100)

question

heart disease death rate of city is 2x that of nation (40/20)

answer

heart disease death rate of city is 2x that of nation (40/20)

question

public health surveillance gain knowledge by (4) and involves (3)

answer

-data collection, data analysis, interp, dissemination of info involves public, HC provider, health agencies

question

goal of public health surveillance attained by?

answer

improved public health via public action attained by identifying public health problems, set priorities, plan health programs, implement health programs, evaluate health programs

question

10 essential public health services

answer

monitor health status to ID probs diagnose and investigate health probs inform public on health issues develop policies supporting public health enforce public health laws and regulations link people to needed health services assure a competent public health workforce evaluate effectiveness accessibility and quality of public health services reserach innovative solutions to health problems

question

public health surveillance monitors population health to

answer

detect sudden changes in disease occurrence follow secular long term trends in disease id changes in disease agents/hosts detect changes in health practices detect potential terrorist activities

question

public health surveillance requires source of data

answer

mortality data sources: vital stats:birth, death, marriage, divorce data records state and local 122 cities in us report death by age and cause to CDC ~1/3 of US deaths, CDC publishes weekly summary in MMWR CDC natnl center for health stats-national sampling of death certif. that goes into natnl mortality followback survey, looks for risk factors and causes of death medical examiners and coroners-med ex appointed physician or pathologist traine din death invest, coroner elected layperson using medical personell to investigate; investigate sudden, suscpicious, violent, unattended,unexplained death and rpt to county/state principal tool-autopsy--research conclusion on cause/manner of death

question

notifiable disease reports

answer

each state decide what health event reportable by health care provider states range widely in what is required NATTIONAL ELECTONIC TELECOMM SYS for SURV is a computerized sys by CDC with weekly data regarding cases of natiaonally notif diseases

question

lab data

answer

diseae may require lab confirm to diagnose

question

hospital data

answer

hosp keep computerized discharge records for financial reasons NCHS performs natnl random sapling and complies an anual natnal hosp discharge report monitoring ER visist to detect disease outbreaks early0may provide first evidence terroism

question

outpatient data

answer

NCHS randmoly samples shopital emergency and outrbeak info and cmpiles it into natnl hostpital ambulaotry medical care survey

question

cancer regittries

answer

45 stats collect data on paitient, type, site, treatment

question

adverse drug rxn

answer

FDA tracks probs of marketed drugs via physican/pharmacist

question

injury surveillence

answer

NHTSA natnl highway traffic safty admin tracks fatal crahses on public roads

question

occupational illness

answer

info from federal OSHA occupat safely and health admin or state agency equiv

question

types of surveys to collct public health data

answer

general pop health surveys -NCHS periodic random sampl US pop health Ntnl health and nutriiton exam survey -behav risk factor surv system (smoking, etc) cross sectional telephone survey

question

diseae indicator surveys

answer

animal population survye evn survye drug utiliz survey sutdnet emplyee

question

animal pop suvey

answer

morb/mortal in animal pop due to zoonoess; presence of diseae agents wild/domestic animals; presence of diseae agent in vector; cahgne in size/dist of potential reservoi vector pop

question

env survay

answer

health dept sample food milk water for diseae agents; health dept loate potential breeding site vector; occupat health dept chack job related ehatlh

question

drug util survgey

answer

state health CDC onlyu source for inrequent drugs; pentamidine-anti penumocysits drug the request upsurge 1981 IADS

question

student survey

answer

school absence flu

question

employee

answer

worker comp claims help asses occu injuryu

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