measurements in epidemiology

1. Measurements ofMeasurements of
Health and diseaseHealth and disease

2.  The simplest and most frequentlyThe simplest and most frequently
performed quantitative measurement inperformed quantitative measurement in
epidemiology is a count of the numberepidemiology is a count of the number
of persons in the group who have aof persons in the group who have a
particular disease or a particularparticular disease or a particular
characteristics, for example, it may becharacteristics, for example, it may be
noted that to people in two collegenoted that to people in two college
dormitories developed infectiousdormitories developed infectious
hepatitis type A.10 students in the firsthepatitis type A.10 students in the first
one and 20 students in the second .one and 20 students in the second .

3. ProportionProportion::
 For a count to be descriptive of aFor a count to be descriptive of a
group it must be seen in proportiongroup it must be seen in proportion
to it; that is must be divided by theto it; that is must be divided by the
total number in the group. The 10total number in the group. The 10
hepatitis cases would have quitehepatitis cases would have quite
differences significance for thedifferences significance for the
dormitory housed 20 student than ifdormitory housed 20 student than if
it housed only500.it housed only500.

4. 
InIn the first case the proportion would bethe first case the proportion would be
0.5 (50%). In the second case the0.5 (50%). In the second case the
proportion would be 0.02(2%) The useproportion would be 0.02(2%) The use
of denominators to convert counts intoof denominators to convert counts into
proportion seems simple to mention. Aproportion seems simple to mention. A
proportion is one basic way to describeproportion is one basic way to describe
a group. It is important to enumeratea group. It is important to enumerate
appropriate denominators in order toappropriate denominators in order to
describe and compare groups in adescribe and compare groups in a
meaningful and useful way.meaningful and useful way.

5. RatioRatio
 Is numerical expression, whichIs numerical expression, which
indicates the relationship inindicates the relationship in
quantity between two parts, thequantity between two parts, the
ratio of male to female is 2:1.ratio of male to female is 2:1.

6. RateRate
A rate is the quantity, amountA rate is the quantity, amount
or degree of somethingor degree of something
measured inmeasured in specific periodspecific period
of time.of time.

7. Population at riskPopulation at risk
 Is that part of population that isIs that part of population that is
potentially susceptible to the diseasepotentially susceptible to the disease
studied.studied.
 For instance, men should not beFor instance, men should not be
included in calculation of carcinoma ofincluded in calculation of carcinoma of
the cervix. Occupational injuries occurthe cervix. Occupational injuries occur
only among working peopleonly among working people
(workforce).(workforce).

8. PrevalencePrevalence::
 The number of existing cases dependsThe number of existing cases depends
on the number of people who developon the number of people who develop
their illness in the past and havetheir illness in the past and have
continued to be ill at the present time.continued to be ill at the present time.
 Period prevalencePeriod prevalence The presence ofThe presence of
particular disease over a longerparticular disease over a longer
period.period.

9. IncidenceIncidence::
 Is defined as the number (No.)Is defined as the number (No.)
ofof new casesnew cases of diseaseof disease

10. Incidence rateIncidence rate::
 No. of new cases in theNo. of new cases in the
population during specificpopulation during specific
period/ no of population at riskperiod/ no of population at risk
of developing the disease at thatof developing the disease at that
period .period . Incidence is the measureIncidence is the measure
of disease developing in a personof disease developing in a person
who did not have the disease .who did not have the disease .

11. Factors of`Factors of`InfluencingInfluencing
prevalence rateprevalence rate::
1.The number of1.The number of new casesnew cases
2.The severity of illness2.The severity of illness
3.The duration of illness3.The duration of illness

12. Period prevalencePeriod prevalence::
 The prevalence of a particularThe prevalence of a particular
disease in a longer period such asdisease in a longer period such as
one month , six months , one yearone month , six months , one year
or even more (life time prevalence)or even more (life time prevalence)

13. Point prevalencePoint prevalence::
 Is used to know how much of aIs used to know how much of a
particular disease is present in aparticular disease is present in a
population at a particular point inpopulation at a particular point in
time , example Dec. , 31, 2010.time , example Dec. , 31, 2010.

14. Incidence
Cure Death
Prevalence
Relationship between incidence
and prevalence
Prevalence = Incidence × average duration of dis.

15. 2009
31-Dec.
2010
31-Dec.

16. IncidenceIncidence is a measure of a diseaseis a measure of a disease
developed in a person who did notdeveloped in a person who did not
have the diease ( transition fromhave the diease ( transition from
non disease to disease status , anynon disease to disease status , any
person in the Y ( denominator )hasperson in the Y ( denominator )has
the potential to become part of thethe potential to become part of the
group that is counted in thegroup that is counted in the
numerator (X)numerator (X)

17. The important point in incidence isThe important point in incidence is
that whatever time period is used inthat whatever time period is used in
the calculation must be clearlythe calculation must be clearly
specified , and all individualsspecified , and all individuals
included in the calculation mustincluded in the calculation must
have been observed ( at risk ) forhave been observed ( at risk ) for
the entire period .the entire period .

18. tools used to evaluate the health status oftools used to evaluate the health status of
the community .the community .
By vital statistics we refer to dataBy vital statistics we refer to data
collected from ongoing recordingcollected from ongoing recording
,registration of all vital events ( birth,,registration of all vital events ( birth,
deaths ,fetal deaths ,marriages anddeaths ,fetal deaths ,marriages and
divorces .divorces .
The physician is responsible for fillingThe physician is responsible for filling
the certificates of death , birth and fetalthe certificates of death , birth and fetal
deathdeath
Vital statisticsVital statistics::

19. Measures of fertilityMeasures of fertility::
Fertility refers to actual bearing ofFertility refers to actual bearing of
children .children .

20. Crude Birth Rate (CBRCrude Birth Rate (CBR((
K
)populationyearmid(Average
)yeara(duringbirthsliveof.No
×

21.  Crude Birth Rate (CBR)Crude Birth Rate (CBR) ::Is theIs the
No. of live births per 1000No. of live births per 1000
population of certain locality andpopulation of certain locality and
year .year .
1000
localityyearmid
yearandlocalitycertainofbirthsliveof.No
×

22. General fertility rateGeneral fertility rate
Κ×
45yrs)-15(agebearinchildofwomenofNo.Total
)yeara(duringbirthsliveofNo.

23. Age specific fertility rateAge specific fertility rate
Κ×
agespecifiedtheofwomenofNo.Total
agecertainaofwomenthebirth toliveofNo.

24. Total Fertility RateTotal Fertility Rate::
The average No. of children thatThe average No. of children that
would be born to womenwould be born to women
surviving until menopause.surviving until menopause.

25. Birth rate is generally high in developingBirth rate is generally high in developing
countries including Iraq , due to :countries including Iraq , due to :
1- high fertility rates due social and1- high fertility rates due social and
traditional motives .traditional motives .
2- poor family planning facilities2- poor family planning facilities
33–– factors related to marriage ( thefactors related to marriage ( the
youngest age of marriage is associatedyoungest age of marriage is associated
with long childbearing period .with long childbearing period .

26. MORTALITY RATESMORTALITY RATES
A mortality rate is a measure of theA mortality rate is a measure of the
frequency of occurrence of death in afrequency of occurrence of death in a
defined population during a specifieddefined population during a specified
interval .interval .

27. Crude Death Rate ( CDRCrude Death Rate ( CDR( =( =
Κ×
yearsametheof(MYP)populationYearMjd
causesandagesallfordeathsofNo.Total
Age specific death rateAge specific death rate::
Mortality at specific age group .Mortality at specific age group .

28. Infant Mortality RateInfant Mortality Rate
 The infant is the baby in the first yearThe infant is the baby in the first year
of life (the baby below one year of ageof life (the baby below one year of age((
 Infant Mortality Rate : It is the numberInfant Mortality Rate : It is the number
of deaths of infants (below one year)of deaths of infants (below one year)
per 1000 live births in a certain localityper 1000 live births in a certain locality
(or country) and year(or country) and year

29. Infant Mortality Rate IMRInfant Mortality Rate IMR
Κ
year&localitysamethebirthsliveof.NoTotal
year&localitycertainainageofyear1underDeathsof.No
×
What is the infant mortality rate inWhat is the infant mortality rate in
Iraq during the year 2013 ????Iraq during the year 2013 ????

30. Neonatal Mortality Rate NMRNeonatal Mortality Rate NMR
Is the number of deaths ofIs the number of deaths of
infants during their firstinfants during their first
month (or 4 weeks) per 1000month (or 4 weeks) per 1000
live births in a certain localitylive births in a certain locality
and yearand year

31. PostPost –– neonatal Mortality Rateneonatal Mortality Rate
 Is the number of deaths ofIs the number of deaths of
infants from one month to oneinfants from one month to one
year of age per 1000 live births inyear of age per 1000 live births in
a certain locality (or country)a certain locality (or country)
and year.and year.

32. Children 1-4 years MortalityChildren 1-4 years Mortality
 It is age specific mortality of preschoolIt is age specific mortality of preschool
children and so called preschool childchildren and so called preschool child
mortality . It is the number of death ofmortality . It is the number of death of
children aged 1-4 years per 1000children aged 1-4 years per 1000
children of the same age group in achildren of the same age group in a
given locality or country and yeargiven locality or country and year

33. Stillbirth RateStillbirth Rate
 Stillbirth is a viable fetus delivered afterStillbirth is a viable fetus delivered after
the 28the 28thth
week of pregnancy withoutweek of pregnancy without
showing any sign of life after beingshowing any sign of life after being
completely expelled from mothercompletely expelled from mother
 Stillbirth rate is the number of fetalStillbirth rate is the number of fetal
deaths after the 28deaths after the 28thth
week of pregnancyweek of pregnancy
per 1000 liveborn in a locality and yearper 1000 liveborn in a locality and year

34. Perinatal Mortality RatePerinatal Mortality Rate
 Perinatal period :is the period aroundPerinatal period :is the period around
labour fom 28labour fom 28thth
week of pregnancy toweek of pregnancy to
the end of first week after labourthe end of first week after labour
 Perinatal Mortality Rate: It is thePerinatal Mortality Rate: It is the
number of death occurring in thenumber of death occurring in the
perinatal periodperinatal period , from 28, from 28thth
week ofweek of
pregnancy to the end of first week afterpregnancy to the end of first week after
labourlabour per 1000 liveborn in a givenper 1000 liveborn in a given
locality and yearlocality and year

35. Maternal Mortality Rate MMRMaternal Mortality Rate MMR
 Maternal mortalityMaternal mortality means death ofmeans death of
mother due to causes related tomother due to causes related to
pregnancy labour and puerperiumpregnancy labour and puerperium
.Risk is more with abortion and ectopic.Risk is more with abortion and ectopic
pregnancy and during child birth andpregnancy and during child birth and
early puerperiumearly puerperium
 Maternal MortalityMaternal Mortality RateRate :Is the number:Is the number
of deaths of mothers due to causesof deaths of mothers due to causes
related to pregnancy labour andrelated to pregnancy labour and
puerperium per 100000 live born in apuerperium per 100000 live born in a
given locality and yeargiven locality and year

36. Maternal Mortality Rate MMRMaternal Mortality Rate MMR==
000001
yeasrandlocalitysamein thebirthsliveTotal
puerperiumandlabourpregnancyto
relatedcausestoduemotherofdeathofNo.
×

37. Case Fatality Rate (CFRCase Fatality Rate (CFR((
 It is the number of deaths of aIt is the number of deaths of a
particular disease per 100 cases in aparticular disease per 100 cases in a
certain locality and year .certain locality and year .
 In outbreaks of a disease in a confinedIn outbreaks of a disease in a confined
community case fatality rate is thecommunity case fatality rate is the
number of deaths per 100 diagnosednumber of deaths per 100 diagnosed
cases during a definite period of timecases during a definite period of time
(period of outbreak)(period of outbreak)

38. Case Fatality Rate (CFRCase Fatality Rate (CFR(=(=
1000
areaorperiodcertainaindiseasethatofcasesAll
diseasecertainafromdeathsAll
×

39. Cause Specific Mortality Rate CSMRCause Specific Mortality Rate CSMR
It is used for chronic disease for exampleIt is used for chronic disease for example
pulmonary T.B. where accurate number ofpulmonary T.B. where accurate number of
cases occurring within the year is notcases occurring within the year is not
available and so case fatality rate can notavailable and so case fatality rate can not
be obtainedbe obtained
1000
localityandyearsametheMYPof
diseasecertainafromdeathsAll
×

40. Proportionate Mortality RateProportionate Mortality Rate
PMRPMR
Is the percent or proportion of theIs the percent or proportion of the
number of deaths of a particularnumber of deaths of a particular
disease to total death in a certaindisease to total death in a certain
locality (or community or group of thelocality (or community or group of the
population )and yearpopulation )and year

41. Exercise No.1Exercise No.1

42. Total midyearTotal midyear
populationpopulation
8000080000
No. of live birthsNo. of live births 20002000
Population aged 45Population aged 45
years and moreyears and more
2000020000
Reported fetal deathsReported fetal deaths 3232
Maternal deathsMaternal deaths 11
Total deathTotal death 648648

43. Death under 1 yearDeath under 1 year 4242
Death of person 45+Death of person 45+
yearsyears
300300
Death due to heartDeath due to heart
diseasedisease
9898
Death due to cancerDeath due to cancer 6060
Death due to strokeDeath due to stroke 4848
Cases of heart diseaseCases of heart disease 10001000
Cases of cancerCases of cancer 12001200

44. CalculateCalculate
 1.Crude Birth Rate1.Crude Birth Rate
 2.Crude Death Rate2.Crude Death Rate
 .3.Infant Mortality Rate.3.Infant Mortality Rate
 4.Maternal Mortality Rate4.Maternal Mortality Rate
 5.Age Specific Mortality Rate 45+5.Age Specific Mortality Rate 45+
 6.Proportionate Mortality Rate due to6.Proportionate Mortality Rate due to
strokestroke
 7.Cause Specific Death Rate due to7.Cause Specific Death Rate due to
cancercancer

45. Exercise No.2Exercise No.2

46. Assume that in a population of 100000Assume that in a population of 100000
persons 20 have disease X in 1 year 18persons 20 have disease X in 1 year 18
die from that disease what are thedie from that disease what are the
mortality rate of that disease? and whatmortality rate of that disease? and what
is the case fatality rate? and what doesis the case fatality rate? and what does
this means to you ?this means to you ?