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PPHS 602 Public Health > From exercises, assignments, and practice exam > Flashcards

From exercises, assignments, and practice exam Flashcards

1
Q

If asked about a country’s reproductive rates, which would give you more information, the gross reproduction rate or the net reproduction rate?

A

The net reproduction rate, because it takes into account the mortality of women during childbearing years

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2
Q

Total Fertility Rate (TFR) formula?

A

(Sum of age-specific fertility rates) x (interval range)/1000

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3
Q

What is the interpretation of Total Fertility Rate (TFR)?

A

Expected number of births per woman if:

  • she experiences the current age-specific fertility rates of the population
  • lives to the end of her childbearing years

It is a cross-sectional measure.

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4
Q

General Fertility Rate (GFR) formula?

A

births/midyr 15-49 female population x 1000

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5
Q

Gross Reproductive Rate (GRR) formula?

A

TFR *pw

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6
Q

What is the interpretation of Gross Reproductive Rate (GRR)?

A

Average number of female offsprings born to a woman over her childbearing years

It is a cross-sectional measure.

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7
Q

If I’m given the sex ratio (SR), how do I calculate the pw?

A

Sex Ratio is #males/#females

pw = 1/(1+SR)

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8
Q

Perinatal mortality rate formula?

A

(#still births + #deaths <8 days)/all live+still births x 1000

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9
Q

Neonatal mortality rate formula?

A

deaths < 28 days/live births x 1000

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10
Q

Infant mortality rate formula?

A

deaths < 1yr/live births x 1000

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11
Q

Maternal mortality rate formula?

A

puerperal deaths/live births x 1000

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12
Q

Rate of natural increase (RNI) formula?

A

(Crude Birth Rate/1000 - Crude Death Rate/1000)*100

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13
Q

Population growth rate (r) formula?

A

(ln P2 - ln P1)/time

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14
Q

Doubling time formula?

A

ln 2/r = (ln 2)/[(ln P2 - ln P1)/time]

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15
Q

Interpretation of Health-Adjusted Life Expectancy (HALE)?

A

May expect to live the equivalent of x years of good health

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16
Q

Interpretation of DALYs?

A

Total of years of life lost due to mortality/morbidity

  • it’s a gap measure
  • it is disease specific
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17
Q

What is the difference between fertility and fecundity?

A

Fecundity is how many people are able to give birth

Fertility is how many people are actually giving birth (influenced by fecundity and social norms)

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18
Q

Describe the 5 phases of demographic transitions

A

Stage 1: High deaths, high births
Stage 2: Rapid death decrease; slow birth decrease = pop increase
Stage 3: Rapid birth decrease; slow death decrease = pop increase
Stage 4: All stable
Stage 5: Pop declining

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19
Q

How to determine that a measure is cross-sectional?

A

It has been taken in only one point in time (e.g., 2009)

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20
Q

In 1999, the life expectancy at birth in Zambian males was approximately 38 years. However, at age 5 it was approximately 41 years. Why is life expectancy seemingly higher at age 5 than at birth?

A

Because life expectancy assumes that you live up to that point. Given that infants are more likely to die than children aged 5 and up, they have a shorter life expectancy than children at age 5. To think of it another way, most child deaths occur in infancy. Once a child has survived infancy, their life expectancy improves because there are fewer deaths in children aged 5 and up.

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21
Q

Why do countries with lower life expectancies require higher TFR for replacement?

A

TFR needed for replacement depends on how many women survive to mean reproductive age (age 25 or 30). If a large percentage of women do not survive to this age, the TFR for replacement must be higher. Alternatively, if most women do not reach the end (or even middle) of their childbearing years, the women who are in their childbearing years must have more children to make up for this loss.

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22
Q

Similarities between QALYs and DALYs?

A
  • Measure population health by considering simultaneously mortality and morbidity
  • Apply Health-Related Quality of Life (HRQL) weights to health states
  • Range from 0 to 1 (QALY, 1: perfect health; DALY, 1: equivalence to death)
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23
Q

Differences between QALYs and DALYs?

A
  • QALY is life expectancy measure while DALY is a gap measure
  • HRQL weights are attached to specific diseases for DALYs (1=death, 0=perfect health), whereas for QALYs the weights are attached to health states (1=perfect health, 0=death).
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24
Q

What is the interpretation of a SMR of, say, 2.21?

A

There were 121% more deaths than expected according to the age-specific mortality rates of REF POP

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25
Q

What is the interpretation of a crude death rate?

A

ON AVERAGE, there were xx deaths per 1,000 people in YEAR in PLACE.

26
Q

How do you compute age-adjusted death rates?

A
  1. Apply age-specific death rates to reference population
  2. Sum the expected deaths
  3. Divide the #expected deaths/totalref population
27
Q

What is the interpretation of an age-adjusted death rate?

A

The age-adjusted death rate in PLACE in YEAR was x deaths per 1000 people, assuming the age distribution of the REFERENCE population.

28
Q

What is the formula of standardized mortality rate (SMR)?

A

observed/expected

29
Q

What is the interpretation of a SMR of, say, 0.76?

A

There were 24% fewer deaths than expected according to the age-specific mortality rates of REF POP

30
Q

How would not reporting citizen deaths affect estimations of life expectancy?

A

Will overestimate life-expectancy (time lived by population/deaths in population):

  • This would increase the number of years added into the equation for average life expectancy while keeping the population denominator the same (ex. If death is only reported 1 year after for everyone, life expectancy will be 1 year longer).
31
Q

How would not reporting infants births until it is clear that they will survive affect estimations of life expectancy?

A

Will overestimate life-expectancy (time lived by population/deaths in population):

  • Infant deaths add very little to the numerator of average life expectancy (not even one year), but add one person to the denominator. Infant deaths are
    therefore counted equally in the denominator as people who live to old age, but only contribute a tiny bit to “time lived” in the numerator.
32
Q

Which will have a bigger impact on mis-estimating life expectancy, not reporting deaths of elderly people, or not reporting deaths of infants?

A

Not reporting deaths of infants
- Infants are much farther from the
true life expectancy from elderly people. This means that infants are “outliers”, which can affect the estimate of life expectancy (basically a mean), much more than not reporting deaths of elderly people,
who will be much closer to the mean.

33
Q

In lifetable, adjusted number at risk = …?

A

risk at start of interval - withdrawals/2

34
Q

What happens to our estimation of the risk if we do not take into account losses to follow-up?

A

We underestimate the risk

35
Q

What should you comment on when comparing two Kaplan-Meier curves?

A
  • Overall survival
  • Number of deaths in each
  • Steepness
  • Any point where they diverge?
36
Q

What should you mention when they ask to comment on the pattern of censoring?

A
  • Is there one of the group where there is more censoring?

- What does it tell us, and is it possible that they are informative?

37
Q

What are the types of censoring?

A
  • Right censoring (withdrawals; event occurs after a certain time, but don’t know when) - if unrelated to risk of event, they meet the assumption of “independent censoring”. Competing risks are usually informative; accidental death is usually uninformative. (Informative = problem)
  • Left censoring (event occured before, but don’t know when)
  • Interval censoring
38
Q

3 advantages of survival analysis?

A
  1. Uses data from all subjects at risk
  2. Accounts for incomplete follow-up
  3. Does not require constant risk over time
39
Q

3 assumptions of survival analysis?

A
  1. Censoring is independent of survival (non-informative; i.e., the risk in subjects lost is the same as those not lost)
  2. The risk of outcome is independent of calendar time (no secular trends)
  3. Risk of outcome is constant WITHIN the time time intervals
40
Q

Main difference between actuarial method and the Kaplan-Meier method?

A

Time intervals are determined differently. In the actuarial method, the time-intervals are pre-specified, but in Kaplan-Meier, the time intervals is established by the event occurrences. In Kaplan-Meier, each interval has only one event (unless they occur simultaneously), and we must know the exact time at which the outcome occurred.

41
Q

When would the results from an actuarial method would resemble that of the Kaplan-Meier method?

A

When the intervals in the actuarial method are very small. They’ll be identical if each time interval has only one event.

42
Q

What is lx?

A

people alive at the start of the interval

43
Q

What is dx?

A

deaths during the interval

dx = lx * qx
# deaths = #people start * age-specific prob of death

44
Q

What is qx?

A

age specific probability of death

45
Q

What is Lx?

A

Person-time lived during the interval

Lx = lx - dx/2
Person-Time lived during interval = #people start - #deaths/2

46
Q

What is Tx?

A

Total person-time lived by cohort above age x

Take last row, add up the previous Lx, each time

47
Q

What is ex

A

Remaining life expectancy of persons live at age x

ex = Tx/lx

48
Q

What is the interpretation of an age-specific probability of death in a life table?

A

This is a conditional probability of death given entry into the interval. Example, for individuals aged 65, they have a 0.95% change of dying during a one-year interval.

49
Q

What is the interpretation of an ex in a life-table?

A

Or, people who were x years old in YEAR in PLACE were expected to live on average y more years, respectively.

50
Q

What are the 9 columns needed for survival analyses using the actuarial method?

A
  1. Time
  2. # at risk start of interval
  3. # of deaths
  4. # of withdrawals
  5. ADJUSTED # AT RISK
  6. PROB OF DYING DURING INTERVAL
  7. COND PROB OF SURVIVAL
  8. CUMULATIVE PROB OF SURVIVAL
  9. CUMULATIVE PROB OF DEATH
51
Q

What are the 8 columns needed for survival analyses using the Kaplan-Meier method?

A
  1. Time
  2. # at risk each time
  3. # of event each time
  4. # withdrawals prior to next time
  5. Prob of event
  6. Con prob of survival
  7. Cumulative prob of survival
  8. Cumulative prob of event

NO ADJUSTED # AT RISK

52
Q

How do we compare two SMRs?

A

We don’t. We can’t compare SMRs because the age-distribution for each cohort is different. We can only compare the study population to the reference population.

53
Q

What is the net reproduction rate?

A

the average number of daughters that would be born to a female (or a group of females) if she passed through her lifetime conforming to the age-specific fertility and mortality rates of a given year. This rate is similar to the gross reproduction rate but takes into account that some females will die before completing their childbearing years.

54
Q

“Calculate the cumulative probability of survival at 15 and 40 days in these patients. Use an actuarial table with 10 day intervals.” What should the intervals be?

A

1-10
11-20
21-30
31-40

55
Q

Doubling time?

A

approx. 70/RNI

(RNI = [CrudeBirthRate/1000 - CrudeDeathRate/1000] x 100

56
Q

What is a stable population?

A

When age distribution and growth rate are constant

  • population can still change size
  • no migration
57
Q

What is a stationary population?

A

When the growth rate is 0, and the age distribution and size are constant

58
Q

Case fatality rate formula?

A

deaths from disease/#new cases of disease x 100

59
Q

Key assumption in survival analysis related to left censoring?

A

Those who enter the study at time t are a random sample of those in the population still at risk at t

60
Q

Which type of censoring is easier to deal with?

A

Right censoring, given that it is non informative

61
Q

Why is the mean duration of survival an undesirable measure?

A
  • Cannot use the loss to follow-up or event did not occur data
  • Bias depending on whether we include them or not
  • Mean is affected by outliers
62
Q

If I have to make a survival curve, what are the axes?

A

X: years since…
Y: % survival

PPHS 602 Public Health (12 decks)

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