Lecture 4 (7/13/16)

Question 1

Mortality indices

Answer 1

mortality rates
case fatality
proportionate mortality
problems with mortality data
comparing mortality rates

Question 2

Mortality rates - deonominator

Answer 2

rates usually calculated on an annual basis
midpoint popuation used = assume all ppl observed for 1 year
midpoint population = # of person-years

Question 3

Person-time in the Annual Mortality Rate

Answer 3

Number of persons in the population at mid year = Number of persons in the population at midyear x 1 year

Question 4

What adds people to the denominator of midpoint population?

Answer 4

Births

Immigrants

Question 5

What remove people from denominator of midpoint population?

Answer 5

Deaths

Emigrants

Question 6

Annual Mortality Rate from all causes per 1000 population

Answer 6

Total number of deaths from all causes in 1 year / Number of peersons in the population at midyear x 1 year x 1000

Question 7

What types of mortality rates can you calculate?

Answer 7

all causes, specific causes, total population, population subgroups, exposure subgroups

Question 8

Cause-specific mortality rate

Answer 8

ex. lung cancer
# of deaths from lung cancer per year / # of persons in population at mid year x 1 year x 1000

Question 9

Case Fatality

Answer 9

‘Rate’ is a proportion
Percent of persons with a disease who die from that disease
# individuals dying during a specified period of time after disease onset/diagnosis / # individuals with specified disease

Question 10

Artifactual differences in case fatality

Answer 10

statistical sampling

surveillance/reporting bias

Question 11

Real differences in case fatality

Answer 11

Comorbidity
Differential pathogenicity
Population differences in susceptibility

Question 12

When is a mortality rate a good index of an incidence rate?

Answer 12

When the case-fatality is high

When duration of the disease is short

Question 13

Proportionate Mortality

Answer 13

• is a PROPORTION
  Percent of deaths due to a specific cause of death
  # of deaths due to specific cause / total # of deaths

Question 14

What is age-adjustment?

Answer 14

A technique for standardizing rates from different populations to the structure of one, common population

Question 15

Direct age-adjustment

Answer 15

data needed from study pop: age-specific death rates
age-specific rates from: study population
population structure from: standard population
comparison of: age-adjusted rates

Question 16

Indirect age-adjustment

Answer 16

data needed from study pop: age-structure, total death
age-spefici rates from: standard population
population structure from: study population
comparison of: standardized mortality ratio (SMR)

Question 17

Standardized Mortality Rate (SMR)

Answer 17

observed # of deaths per year / expected # of deaths per year

Question 18

Advantages & Disadvantages of Crude Rates

Answer 18

Advantages:
actual summary rates - “observed events”
readily calculable for international studies (widely used despite limitations)
Disadvantages
- since populations vary in composition (e.g. age), differences in crude rates are difficult to interpret

Question 19

Advantages & Disadvantages of Specific Rates

Answer 19

Advantages:
- homogenous subgroups
- detailed rates useful for epidemiologic and public health purposes
Disadvantages:
- since populations vary in composition (e.g. age), differences in crude rates are difficult to interpret

Question 20

Advantages & Disadvantages of Adjusted Rates

Answer 20

Advantages:
-represent summary statements
- differences in composition of groups “removed” permitting unbiased comparisons
Disadvantages
- fictional rates - not “real” events
- absolute magnitude dependent on standard population chosen
- opposing trends in subgroups masked

Question 21

Differences between prevalence and incidence

Answer 21

• prevalence is a proportion, incidence is a rate
• incidence measures new cases while prevalence measures any existing cases
• denominator incidence is persons at risk (healthy, non-diseased) while denominator for prevalence is the total population (including both sick and healthy)

Question 22

Differences between incidence and cumulative incidence

Answer 22

• incidence rate is a RATE, cumulative incidence is a PROPORTION
• both measure new cases and indicate risk
• time is handled different. time is integral part of denominator for incidence (calculate rates), but not for cumulative incidence (time interval simply referenced)

Question 23

Classifying causes of death

Answer 23

death certificates

ICD