Epidemiological Measurements Of Morbidity And Mortality

Question 1

WhT are epidemiological measures

Answer 1

Epidemiologic measures represent an application of common mathematical terms to the description of the health of the population

Question 2

Epidemiologic measures provide information on:
•The frequency of a disease or condition
•Associations between exposures and health outcomes
•Strength of the relationship between an exposure and a health outcome

True or false

Answer 2

True

Question 3

What must you consider in defining the numerator and denominator

Answer 3

Defining the numerator
•Case definition (condition) — carefully defined in a manner that can be replicated by others
•Frequency—How many cases are there?
•Severity—Some epidemiologic measures employ morbidity as the numerator and others use mortality
•Defining the denominator
•Does the measure make use of the entire population or a subset of the population?
•Some measures use the population at risk

Question 4

What is the The simplest and most frequently performed quantitative measure in epidemiology and explain it

Answer 4

Count and it is the Refers to the number of cases of a disease or other health phenomenon being studied

• Significant for rare diseases or symptom presentations
• e.g., case of Ebola virus

Question 5

Ratio is a value obtained by dividing one quantity by another

The most general form has no specified relationship between numerator and denominator
•Proportions, percentages, and rates are also ratio

Give two examples of ratio

Answer 5

Gender ratio
Male divided by female is equal to Male:Female

Example- 950/50 females is equal to 19 males : 1 female

Question 6

What is proportion and what is it used for

Answer 6

measure that states a count relative to the size of the group.

•A ratio in which the numerator is part of the denominator.

• May be expressed as a percentage
• A percentage is a proportion that has been multiplied by 100

Use-Can demonstrate the magnitude of a health problem relative to size of a group
•Example:
•10 dormitory students develop hepatitis.
•How important is this problem:
•If only 20 students live in the dorm?
•0.50 (50%) are ill.

Question 7

What is rate and what elements does it contain

Answer 7

a ratio that consists of a numerator and a denominator and in which time forms part of the denominator.
•Contains the following elements:
•disease frequency
•unit size of population
•time period during which an event occurs

Question 8

What are the measures of disease frequency in epidemiology and state em

Answer 8

The term incidence refers to the occurrence of new disease or mortality within a defined period of observation (e.g., a week, month, year, or other time period) in a specified population.

Prevalence
•The number of existing cases of a disease or health condition in a population at some designated time

Question 9

Name and explain the types of incidence

Answer 9

Cumulative Incidence
•Describes the rate of development of a disease in a group over a certain time period.
•Contains three elements:
•Numerator = the number of new cases.
•Denominator = the population at risk.
•Time = the period during which the cases occur.

Incidence rate
•An incidence measure used when members of a population or study group are under observation for different lengths of time.

Question 10

Who are the population at risk

Answer 10

members of the population who are capable of developing the disease or condition being studied

Question 11

Uses of incidence data

Answer 11

the effects of exposure on health outcomes
•the risks associated with certain exposures; “. . . the probability of someone in that population developing the disease during a specified period, conditional on not dying first from another disease.”

Question 12

Formula for cumulative incidence is

Answer 12

Cumulative incidence Rate
Cumulative incidence =
Number of new cases
over a time period

  Total population at risk
during the same time period
X multiplier (e.g., 100,000)
Number of new cases = 1,085
Population at risk = 37,105
Period =8 years
Cumulative Incidence =
1,085
37,105
= 0.02924/8
= 365.5 cases per 100,000 women per year
= 0.003655 x 100,000

Question 13

Formula for incidence rate

Answer 13

1. Cumulative incidence rate: number of new cases during the time period divided by total person time observation
2. incidence rate:number of new cases during the time period divided by total person years observation

Question 14

Person- years is equal to the sum of the number of subjects times the total duration of the lengths of observation

True or false

Answer 14

True

Question 15

Name and explain the types of prevalence with their formulas

Answer 15

Point Prevalence

•All cases of a disease, health condition, or deaths that exist at a particular point in time relative to a specific population from which the cases are derived

Point Prevalence

Point Prevalence =
Number of persons ill
Total number in the group
at point in time

Example:

Total number of smokers in the group = 6,234
Total number in the group 41,837
or 14.9%
= 149.0 per 1,000
Loading…

Period Prevalence

•All cases of a disease, health condition, or deaths that exist within a point of time relative to a specific population from which the cases are derived

                                   Number of persons ill over a period of time divided by Average population

Example:
People who have been diagnosed w cancer divided by average population

Question 16

Prevalence of diarrhea in a children’s camp on July 13 was 33% is an example of what type of prevalence and Prevalence of cancer in women during between July 13 and July 30 period was 33% is another example of what type of prevalence

Answer 16

Point and period prevalence

Question 17

Uses or prevalence

Answer 17

Provides an indication of the extent of a health problem.

Describing the burden of a health problem in a population.

• Estimating the frequency of an exposure.
• Determining allocation of health resources such as facilities and personnel.

Question 18

What causes increased or decreased prevalence

Answer 18

Increased prevalence
•Longer duration of the disease
•Prolongation of life of patients without cure
•Increase in new cases (increase in incidence)
•In-migration of cases
•Out-migration of healthy people
•In-migration of susceptible people
•Improved diagnostic facilities (better reporting)

Decreased prevalence
•Shorter duration of disease
•High case-fatality rate from disease
•Decrease in new cases (decrease in incidence)
•In-migration of healthy people
•Out-migration of cases
•Improved cure rate of cases

Question 19

Prevalence is equal to incidence rate times duration true or false

Answer 19

True

Question 20

When does prevalence become similar to incidence

Answer 20

If duration of disease is short and incidence is high, prevalence becomes similar to incidence.

If duration of disease is short and incidence is high, prevalence becomes similar to incidence.
•Short duration–cases recover rapidly or are fatal.
•Example: common cold

Question 21

When does prevalence increases greatly relative to incidence

Answer 21

If duration of disease is long and incidence is low, prevalence increases greatly relative to incidence.
•Example: many chronic diseases

Question 22

Types of rates

Answer 22

Crude Rates
•Specific Rates
•Adjusted Rates

Question 23

Where an incidence rate applies to an entire population, it is referred to as a crude rate.

True or false

Answer 23

True

Question 24

Formula for crude death rate and crude birth rate

Answer 24

Number of deaths in a given year divided by reference population during midpoint of the year multiplied by a reasonable multiplier that’ll give a whole number

Number of live births
within a given period
Divided by
Population size at the
middle of that period times a reasonable
Multiplier

Question 25

What ar ethe implications of crude rate

Answer 25

Use crude rates with caution when comparing disease frequencies between populations

• Observed differences in crude rates may be the result of systematic factors (e.g., sex or age distributions) within the population rather than true variation in rates
• To correct for systematic population factors that influence crude rates, Specific and Adjusted rates may be constructed

Question 26

What’s re specific rates and give three examples

Answer 26

Rates
•Specific rates refer to a particular subgroup of the population defined in terms of race, age, sex, or they may refer to a entire population, but be specific for some single cause of death or illness.

Examples
•Cause-Specific Rates
•Age-Specific Rates
•Sex-Specific Rates
•Proportional Mortality Ratio

Question 27

What is case specific rate and an example and a formula

Answer 27

The cause-specific rate is a measure that refers to mortality (or frequency of a given disease) divided by the population size at the midpoint of a time period times a multiplier

Example
•Cause-specific mortality rate – rate associated with a specific cause of death

Cause-Specific Rate =
Mortality (or frequency of a given disease)

Population size at midpoint of time peri

Question 28

What is age specific rate and the formula

Answer 28

An age-specific rate refers the frequency of a disease (or health condition) in a particular age stratum divided by the total number of persons within that age stratum during a time period.

Age-Specific Rate =
Number of deaths (or disease) among those aged 15–24 years

Number of persons among aged 15–24 years during time period

Question 29

What is sex specific rate and the formula

Answer 29

sex-specific rate refers to the frequency of a disease in a gender group divided by the total number of persons within that gender group during a time period times a multiplier.

Number of deaths among males = 1,207,675
•Number of deaths among females = 1,240,342
•Estimated number of males in the population as of July 1, 2005 = 145,999,746
•Estimated number of females in the population as of July 1, 2005 = 150,410,658

• Calculate the sex-specific rate for males per 100,000
• = 1,207,675/145,999,746 × 100,000
• = 827.2 per 100,000
• Calculate the sex-specific rate for females per 100,000
• = 1,240,342/150,410,658 × 100,000
• = 824.6 per 100,000.

Question 30

What is proportion mortality rate and the formula

Answer 30

The proportional mortality ratio (PMR) is the number of deaths within a population due to a specific disease or cause divided by the total number of deaths in the population.

•Indicates relative importance of a specific cause of death; not a measure of the risk of dying of a particular cause

PMR (%) =
Mortality due to a specific cause during a time period divided by
Mortality due to all causes during the same time period
X 100

Question 31

What are adjusted or standardized rates

Answer 31

Summary measures of the rate of morbidity and mortality in a population in which statistical procedures have been applied to remove the effect of differences in composition of various populations.

Question 32

What’s re the types of adjusted or standardized rates and explain

Answer 32

Direct Method
•Direct method may be used if age-specific death rates in a population to be standardized are known and a suitable standard population is available
•Each age-specific death rate in the population to be standardized is multiplied by the number of persons in each age group of the standard population
•The result is the expected number of death in each age group, which is then summed across all age groups to determine the number of expected deaths

Indirect method may be used if age-specific death rates of the population for standardization are unknown or unstable, for example, because the rates to be standardized are based on a small population
•The number of persons in each age group in the population to be standardized is multiplied by the age-specific death rate of the standard population
•The result is the expected number of death in each age group, which is then summed across all age groups to determine the number of expected deaths

•

Question 33

The standardized mortality ratio (SMR) can be used to evaluate the results of the indirect method. What is the formula?

Answer 33

Total Observed deaths divided by

Total Expected deaths times 100

Question 34

If the observed and expected numbers are the same, the SMR would be ? And what does it indicate

Answer 34

1.0 (or 100%), indicating that observed mortality is not unusual.

Question 35

If the SMR is less than 1.0 (<100%)?

• If the SMR is greater than 1.0 (>100%) it means?
• E.g. An SMR of 2.0 (200%) means that the death rate in the study population is two times greater than expected true or false

Answer 35

1. it means the death rate is in the study population is less than expected
2. it means the death rate is in the study population is more than expected

True

Question 36

Calculate SMR and crude death rate :SMR is (502/987.9) X 100 = (0.51) 51%. This means what for the death rate?
•The

Answer 36

death rate in the study population of interest is 0.51 (51%) times less than expected

Question 37

What is a hazard, what is a risk

Answer 37

Hazard refers to the potential to cause harm

Hence risk is a statement of probability that an event (death, disease etc) will occur.

Risk

•Thus, risk is a statement of probability that an event (death, disease etc) will occur

•

Question 38

Risk ranges from 0 to 1

• Risk can generally be estimated as the incidence of an event (death, disease etc)
• Therefore rates are an indicator of risk and other measures of risk are Relative risk (risk ratio/rate ratio)
• Attributable risk (Absolute risk difference)

True or false

Answer 38

True

Question 39

A two by two table is useful for doing what?

Answer 39

useful tool for viewing study results and calculating effect measures for comparing groups
•This can be done with relative or absolute effect measures

Question 40

What is relative risk used for and interpretation of relative risk

Answer 40

Relative risk is used to compare the incidence of a disease or condition between a group with a particular attribute or exposure to one without.

Relative risk is a measure of the strength of an association between an exposure or attribute and a disease.

Question 41

If the relative risk is 1 then?

• If it is greater than 1,
• If less than 1,

Answer 41

then the incidence in the two groups is the same.

2. then the attribute or exposure is associated with an increased incidence of the disease,
3. with a decreased incidence of the disease

Question 42

Example of relative risk of getting lung cancer from smoking :is (number of smokers or exposed group with lung cancer divided by number of smokers with no lung cancer plus number of smokers with lung cancer ) all divided by (number of non smokers or non exposed group divided by non smokers w lung cancer divided by non smokers with no lung cancer plus non smokers with lung cancer)
True or false

Answer 42

True

Question 43

What is a risk factor and when an exposure is indentified as a risk factor for a disease what does it mean

Answer 43

Factors which may be causes of the disease and which, if removed or modified, would prevent the disease occurring

• When an exposure or attribute is identified as a risk factor for a disease, it simply means that:
• It is associated with an increased probability (risk) of the disease occurring.
• It does not mean that the factor is a cause of the disease

•For example, over 200 risk factors identified for coronary heart disease (siestas, snoring, English as a mother tongue and not eating mackerel etc)

Question 44

What is attributable risk

Answer 44

Attributable risk is used to provide an assessment of how much of a disease is ‘due to’ an exposure and so we can assess how much might be prevented if an exposure is removed

•Simple the difference in frequency of a disease between two groups (exposed vs. non-exposed),

Question 45

State the types of atributable risks and explain

Answer 45

Attributable risk (exposed)
•Refers to the rate of a disease or condition among exposed individuals that can be attributed to the exposure

•Attributable risk (exposed) = Incidence among the exposed − incidence among non-exposed
Look on slide for formula example

Attributable risk (population) is the rate of a disease or condition among the total population which can be attributed to the exposure.

•Attributable risk (population) = Incidence among total population − incidence among non-exposed

Question 46

Name three interpretations of attributable risk interpretations

Answer 46

That the exposure (in this case smoking) “causes” the disease (lung cancer)

2.That other “causes” of the disease are equally distributed among the exposed (smokers) and unexposed (non-smokers)

•#That the rate of the disease in the exposed group will return to that in the non-exposed if the exposure is removed

Question 47

Name the public health relevance of relative risk and attributable risk

Answer 47

Relative risk and attributable risk provide two very different types of information

• Relative risk is a measure of the strength of the association between an exposure and a disease.
• It is used to help assess whether or not an exposure is one of the ‘causes’ of a disease.

The attributable risk (population) provides an estimate of the benefit that might be expected within the total population if exposure to a given factor is removed

•Thus attributable risk (population) is helpful when guiding preventive health measures aimed at improving the health of a population

Question 48

The strength of the association and whether or not there is a ‘dose response’ relationship between the occurrence of the disease and the exposure are two factors often used to assess if the exposure is likely to be causal. E.g smoking and lung cancer

True or false

Answer 48

True

Question 49

• The potential benefits of removing different exposures can be assessed using attributable risk
• This can be useful in helping to decide which exposures it is worth trying to prevent.

True or false

Answer 49

True

Question 50

Smoking: exposed 80/100 divided by 20/100 non-exposed for relative risk and 80/100 -20/100 for attributable risk interpretation

Answer 50

Relative risk: 80/100 ÷ 20/100 = 4
i.e. those exposed to smoking have 4 times the risk of developing lung cancer as those not exposed to smoking
Attributable risk: 80% - 20% = 60%
i.e. for every 100 people exposed to smoking there will be 60 extra cases of lung cancer.

Question 51

Difference between crude date and specific rates

Answer 51

Crude rate is the rate in which the denominator includes the total population. Specific rate stands for the rate that measures morbidity or mortality for particular population or diseases.