[06.08] Epidemiologic Measurements and Indices_ Disease Frequency and Associations V2.pdf

Health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity

What is the WHO definition of health used in the introduction?

Descriptive level, Etiology level, Treatment level

What are the three levels for which measures of disease frequency and associations are needed?

Describing the distribution of a health problem or disease in relation to the characteristics of the persons, the place and the evolution of the frequency of appearance over time

What is the purpose of measuring disease frequency and associations at the Descriptive level?

Person, place, and time

What are the components of the epidemiologic triangle (recall item)?

Establishing the causal or determinant factors of the disease or health problem being studied

What is the purpose of measuring disease frequency and associations at the Etiology level?

Pathogenesis of a disease

What must be known at the etiology level to proceed to the treatment level?

Evaluation of the potential impact of the measures proposed in relation to the health problem or disease

What is the purpose of measuring disease frequency and associations at the Treatment level?

Health programs that enclose the clinical management

What does the treatment level include, besides clinical and pharmacological management?

Variables that indirectly measure a health status which can not be measured directly

What is the definition of a Health Indicator?

To compare areas or population group at a certain time, and to measure changes over a period of time

What are two uses of health indicators related to comparison and time?

Multidimensional or multifactorial

What is true about the cause of health when ideal health indicators are rare?

Valid

What characteristic of an ideal indicator means it "measures what it is supposed to measure"?

Reliable

What characteristic of an ideal indicator means it "provides the same information under different observations and conditions"?

Sensitive

What characteristic of an ideal indicator means it is "sensitive to changes in the situation"?

Specific

What characteristic of an ideal indicator means it "reflects changes only in that situation"?

Relevant

What characteristic of an ideal indicator means it is "relevant to the community’s needs and problems"?

Feasible

What characteristic of an ideal indicator refers to "the ability to obtain data when needed"?

Description, Forecast/prognosis, Explanation, System management and quality improvement, Evaluation of health interventions, Advocacy, Research and analysis, Measure gender gaps

What are the eight uses of health indicators listed?

Social determinants of health

What are measured using health indicators to address gender gaps?

Mortality indicators, Morbidity indicators, Disability indicators, Nutritional status indicators, Health care delivery indicators, Utilization rates, Social and mental health indicators, Environmental indicators, Socioeconomic indicators, Health policy indicators, Indicators of quality of life (QOL), Other indicators

What are the eleven (plus 'Other') types of health indicators listed?

Incidence and Prevalence

What are the two major categories of Morbidity indicators?

Cumulative incidence and Incidence rate or Incidence density

What are the two sub-types of Incidence indicators?

Number of new cases occurring in a defined population during a specified period of time

What is the definition of Cumulative Incidence?

Rate

What is the tool of measurement for Cumulative Incidence?

Number of new cases of specific disease during a given time period

What is the numerator for Cumulative Incidence?

Population at-risk during that given time period

What is the denominator for Cumulative Incidence?

Per 1,000

What is the common multiplier ($10^n$) for Cumulative Incidence?

Per year (usually a year unless otherwise specified)

What is the time frame for Cumulative Incidence?

Outbreaks, Taking action, Controlling communicable disease, Controlling non-communicable diseases, Research for etiology and pathogenesis, Efficacy of therapeutic and preventive measures

What are six uses of Cumulative Incidence?

1.67 or 2 cases of influenza per 1,000 people per year

What was the calculated Cumulative Incidence from the example of 5,000 new influenza cases in a 3 million mid-year population?

Incidence Density

What is another name for Person-time incidence rate?

Number of new cases occurring in a defined population during a specified period of time

What is the definition of Incidence Density?

Rate

What is the tool of measurement for Incidence Density?

Number of new cases of specific disease during a given time period

What is the numerator for Incidence Density?

Sum of person-time of the at-risk population

What is the denominator for Incidence Density?

Per 1,000 person-years, per 10,000 person-days (varies)

What is the multiplier ($10^n$) for Incidence Density?

Varies

What is the time frame for Incidence Density?

Taking action (outbreak), Control disease (outbreak), Research for etiology and pathogenesis, Efficacy of therapeutic and preventive measures

What are four uses of Incidence Density?

61.9 or 62 per 1,000 sailor-years

What was the calculated Incidence Density for 234 cases among sailors with 3,780 accumulated person-years?

All cases (new & old) existing at a given point in time OR over a period of time in a given population

What does Disease Prevalence refer to?

Point Prevalence and Period Prevalence

What are the two sub-types of Prevalence indicators?

Number of all current cases (new & old) occurring in a defined population at one point in time (a time of day, a day, days, or few weeks)

What is the definition of Point Prevalence?

Proportion

What is the actual tool of measurement for Point Prevalence, even if it is sometimes called a "rate"?

Number of current cases (new & old) at a given point of time

What is the numerator for Point Prevalence?

Estimated population at the same given point of time

What is the denominator for Point Prevalence?

Per 100

What is the multiplier ($10^n$) for Point Prevalence?

Given point of time

What is the time frame for Point Prevalence?

Estimate the magnitude of health, disease, and high-risk populations, Administrative and planning (ex. hospital beds)

What are two uses of Point Prevalence?

Percentage

In what form is Point Prevalence always expressed?

Less common than point-prevalence

How is Period Prevalence described in terms of usage?

Number of all current cases (new & old) occurring in a defined population at a defined period of time (over months or annual)

What is the definition of Period Prevalence?

Proportion

What is the tool of measurement for Period Prevalence, even if it can be referred to as a period prevalence rate?

Number of all current cases (new & old) at a defined period of time

What is the numerator for Period Prevalence?

Estimated population at the same defined period of time

What is the denominator for Period Prevalence?

Per 100 (always expressed as percentage)

What is the multiplier ($10^n$) for Period Prevalence?

Given period of time

What is the time frame for Period Prevalence?

Estimate the magnitude of health, disease and high-risk populations

What is a use of Period Prevalence?

40.7%

What was the calculated Period Prevalence of seasonal allergies (468 cases in 1150 students) in the example?

A snapshot of the population

What does Prevalence give us?

Cases 3, 4, 5, 8

Which cases from Figure 1 are included in Incidence during the period of January 1 to December 31?

Cases 1, 3, 5, 8

Which cases from Figure 1 are included in Point Prevalence on December 31?

Cases 1, 2, 7

Which cases from Figure 1 are included in Point Prevalence on January 1?

Cases 1, 2, 3, 4, 5, 7, 8

Which cases from Figure 1 are included in Period Prevalence during the period of January 1 to December 31?

Case 6

Which case from Figure 1 is excluded from Period Prevalence because it started after December 31?

Community

What does the bathtub represent in the Epidemiologist Bathtub model?

Prevalence of disease

What does the water in the tub represent in the Epidemiologist Bathtub model?

Burden of disease

What does prevalence represent in the context of the community?

Incidence $\times$ Duration of Disease

What is the equation for Prevalence (Equation 5)?

They can recover/be cured or lead to death/die

What are the two ways people who have the disease can be removed, draining the water from the tub?

Incidence rate

What does the faucet represent in the Epidemiologist Bathtub model?

Interventions that we have in our public health programs

What does the faucet represent regarding public health efforts?

Estimate the magnitude of the relation between a factor (exposure) and a health problem or disease (result/outcome)

What is the purpose of Measures of Association or Effect?

Statistical dependence between two magnitudes or variables

What is Association viewed as?

Relative Risk (RR), Incidence Density Ratio (IDR), Odds Ratio (OR), Attributable Risk (ARR), Attributable Fraction

What five specific Measures of Association or Effect are discussed?

Rate of accumulated incidence (AI)

What is Relative Risk (RR) also known as, in relation to incidence?

Ratio of the risk of contracting the disease among a group of exposed subjects compared to the risk among a similar group of unexposed subjects

What is the definition of Relative Risk?

0

What is the minimum possible value for Relative Risk?

$I{Incidence\ rate\ exposed} / I{Incidence\ rate\ unexposed}$

What is the formula for Relative Risk (Equation 6)?

No association, Negative association, Protective effect or Protective factor

What is the interpretation of RR < 1?

Positive association, Exposed group has a greater incidence than the unexposed group in developing an outcome/disease

What is the interpretation of RR > 1?

Rate ratio

What is Incidence Density Ratio (IDR) also called?

Ratio of the incidence density of an exposed group to that of an unexposed one

What is the definition of Incidence Density Ratio?

How many times the event occurs with greatest speed among persons exposed, in comparison to those not exposed to the risk factor being studied

What does IDR express?

$I{Incidence\ density\ of\ the\ exposed} / I{Incidence\ density\ of\ the\ unexposed}$

What is the formula for Incidence Density Ratio (Equation 7)?

Cross-product ratio

What is the Odds Ratio (OR) also known as?

Good estimator of the association between two binary variables

What is OR considered, especially with confidence intervals?

Cohort studies

In what type of studies is Odds Ratio usually seen?

$Odds{Exposed} / Odds{Unexposed}$

What is the formula for Odds Ratio (Equation 8)?

Enables the user/researcher to apply logistic regression to examine the effects of other variables on this relation

What is an important use of OR regarding regression?

Absolute Risk Reduction (ARR)

What is Attributable Risk also called?

Proportion of the incidence of a disease among the exposed population that is due to the exposure

What is the definition of Attributable Risk (AR)?

The incidence of a disease in the exposed/at risk population that would be eliminated if exposure/risk were eliminated

What idea does Attributable Risk give?

Risk difference or Rate difference

What is ARR calculated as the difference between in cohort studies?

$AI{Exposed} - AI{Unexposed}$

What is the correct formula for Attributable Risk Reduction (Equation 9)?

Rare diseases/rare events (less than 10%)

For what type of disease/event are case-control studies traditionally meant, affecting AR calculation?

Indirectly by means of another source of information

How may AR be determined in case-control studies if the disease is a rare event?

Population Risk Excess

What is Population Attributable Risk (PAR) also called?

Proportion of the incidence of a disease in the population (in both exposed and unexposed) that is due to exposure

What is the definition of PAR?

The incidence of a disease in the population that would be eliminated if the exposure were eliminated

What is the key idea behind PAR?

$AI{Population} - AI{Unexposed}$

What is the correct formula for Population Attributable Risk (Equation 10)?