Adjustment of Rates

Question 1

Years of Potential Life lost

Answer 1

• Premature Mortality index

Question 2

True vs. apparent incidence

Answer 2

• True: increase in prevalence of risk factors for outcome

* Apparent: increase/enhancement of diagnostic tools that allow people to detect and diagnose subclinical disease

Question 3

Death Certificate

Answer 3

• underlying cause of death: “the disease or injury which initiated the train of morbid events leading directly or indirectly to death or the circumstances of the accident or violence which produced the fatal injury.”
• The underlying cause of death “excludes information pertaining to the immediate cause of death, contributory causes and those causes that intervene between the underlying and immediate causes of death.”
• Changes in definition of disease affect rate

Question 4

Cohort Effect

Answer 4

• Long term study peak mortality can be observed earlier than visibly seen due to cohort of interest aging through time

Question 5

Future Burden of Disease

Answer 5

• Disability Adjusted Life Years

* (1) DALY = (1) lost year of healthy life

Question 6

Errors in Epidemiology

Answer 6

Random Error (exist no matter what, larger sample reduces error)
		•Systematic Error or Bias
			•Many Types of Systematic Error
			•Non-random samples
			•Non-participation
			•Problems with measurement

Question 7

Confounding

Answer 7

• definition: A factor that distorts the association between the exposure and the outcome.
• Criteria: 1. It is associated with the outcome (disease); 2.It is associated with the exposure [But it is NOT caused by the exposure—precedes exposure]

Question 8

Purpose of Direct Adjustment

Answer 8

• Stratify rates by levels of your confounding variable in each of your exposure groups and then apply those rates to the same levels in a standard population.
• Rates that you can compare knowing you have “adjusted” or “accounted” for your confounding variable.
• If exposed and unexposed groups had the same distribution of con-founder, we would expect the number of expected outcomes to occur (our ending result)
• an adjusted rate is an artificial figure that is useful for comparing the rates between different populations
• Crude rates are still the indicator of absolute mortality/morbidity rates in a population

Question 9

5 Steps for Direct Adjustment

Answer 9

1. Choose (or create) a standard population
   2. Compute the disease rates within each level of the confounding factor for the exposed and unexposed groups separately
   3. Within each level of the confounding factor, multiply the rates by the number of the people in the standard population within that level for the exposed group and then again for the unexposed group
   4. Within each exposure group, sum the number of expected outcomes across levels of the confounding factor.
   5. Divide the total number of expected outcomes for each exposure group (separately) by the total population from the standard population.