3) Measurement of Mortality and Morbidity

Morbidity and Mortality Measurements in a Population

WHY IMPORTANT FOR MEDICAL DOCTOR? WHY IMPORTANT FOR MEDICAL DOCTOR?

AS A CLINICIANAS A CLINICIAN::1.1. Patient DiagnosisPatient Diagnosis2.2. Determine TherapyDetermine Therapy

1.1. Estimate PrognosisEstimate Prognosis2.2. Trend of mortalityTrend of mortality

PREVALENCEINCIDENCEMorbidity

MortalitySURVIVAL RATECASE FATALITY RATE

Greenberg, Epidemiologic Measures, pages 15-23

As a public health doctorAs a public health doctor

1. Diagnose community health problems1. Diagnose community health problems2. Intervention/program evaluation2. Intervention/program evaluation3. Program Management3. Program Management4. Compare community health status4. Compare community health status

ABSOLUTE, RATIO, PROPORTION, RATE

TYPES OF MEASUREMENTTYPES OF MEASUREMENT

ABSOLUTE/FREQUENCY, RELATIVE ABSOLUTE/FREQUENCY, RELATIVE (RATIO, PROPORTION, RATE)(RATIO, PROPORTION, RATE)

CRUDE, SPECIFIC, ADJUSTEDCRUDE, SPECIFIC, ADJUSTED

ABSOLUTEABSOLUTE(Frequency of numerator)(Frequency of numerator)

Logistic planningLogistic planning

Diagnose community health Diagnose community health problem problem

Evaluate programEvaluate program Etiology StudyEtiology Study

Ok X

RATIO

• Def: Comparison between two independent numbers

• Example: • SEX RATIO number of men : number of women

• AIRT and Diarrhea number of AIRT patients : diarrhea patients

• Interpretation ??

X Y

PROPORTIOPROPORTIONN

Def: comparison between two number in Def: comparison between two number in which the numerator is part of the which the numerator is part of the denominatordenominator

Example:Example:– AIRT Proportion from total clinic visitsAIRT Proportion from total clinic visits– TBC proportion from total TBC and HIV in USATBC proportion from total TBC and HIV in USA

Interpretation: ……….Interpretation: ……….

X X + Y

* IN* INCCIDENIDENCECE* PREVALEN* PREVALENCECE

- - What? (What? (DefiniDefinition) tion) - - How to measure ?How to measure ?- - What for? (usageWhat for? (usage))

X X + Y

RATERATE

RATE• A proportion when the denominator is

population “at risk”.• Rate always proportion but not all Rate always proportion but not all

proportion is rate.proportion is rate.Example:

– Crude death rate– Cause specific death rate– Infant mortality rate– Fetal death rate

X X+Y

“RATE” CONDITIONNumerator/ Denominator, Constant, Time

1 2 5 4 3

1. Numerator and denominator have similar characteristics

2. Denominator is population at risk3. Presented in a unit of period4. Stated in a constant of round number (kelipatan 10)6. Denominator is population at certain

geographic area

DEFINITION• Incidence rate: proportion of people

who are previously not suffer for disease and become ill in a period of time toward observed at risk population

• Prevalence: proportion of ill people at a point of time toward observed at risk population

Figure-1

1/1/06 31/12/06500

people

1. Direct observation toward a group of people (primary data).

2. Estimation using secondary data.3. Estimation using prevalence data and

average of illness duration. Formula: P = I x d

Methods to gain incidence rate

INCIDENCE RATE

Method 1. Direct Observation

x x x 1/1/92 30/3/92 31/6/92 30/9/92

31/12/92

Numerator of Incidence rate:• Number of people• Number of incident (Jumlah kejadian)

Sampel 500 pop at risk

Gonorrhea

1/1/06 31/12/06

Case 1

Case 2

Case 3

Case 4

1500 population “at risk”

Method 2. Secondary DataNumerator (those who became ill)

Posyandu, Puskesmas pembantu, Puskesmas, RS, RSUP, Laboratory (Public/private), public/private doctor and paramedic

Denominator (at risk)Population in a certain area at a point of time.1. Population Census2. Estimation of number of population based on

population growth rate and census3. Population Registration or vital statistic.

Method 3: By formula

Prevalence depend on:1.Previous incidence.2.Duration of illness.

P ≈ I x d Only for Chronic Disease

DENOMINATOR of Incidence rate

• Population “at risk”.• Those who are NOT “at risk”:

– Have had ill and become immune – Have immunization– Have been ill at the point of incidence

measurement– Died– “Lost to follow up”

Which population to be denominator?

• Average of population• Initial + End population divided by 2.• Mid-year population or mid-time of

measurement period• “Person years” the most accurate

- Point Prevalence- Period Prevalence

1/1/06 31/12/06

500 people

1/6/06

PREVALENCE RATE

Incidence PrevalenceRisk to suffer for disease (period of time)

Proportion of suffering disease (point of time)

For acute/chronic For chronic

Application:- Etiology- Management

Application:- Management

COMPARISON BETWEEN INCIDENCE AND PREVALENCE