Epi test 2

How does a prevalence proportion (expressed as number of cases per unit size of population) differ from an incidence rate?

A prevalence proportion is formed by dividing the number of cases that occur in a population by the size of the population in which the cases occurred. An incidence rate denotes a rate formed by dividing the number of new cases that occur during a time period by the number of individuals in the population at risk.

What is the relationship between incidence and prevalence?

Period prevalence refers to all cases of a disease within a period of time. But, 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.

10. What is (a) the cause-specific mortality rate for injuries and (b) the case fatality rate (%) for injuries? a. From Table 2-6, the number of fatal injuries is 5 and the total number in the population is 5,837.

The cause-specific mortality rate for injures is (5/5837) X 100,000 or 85.7 per 100,000. b. The number of deaths due to injuries is 5 and the number of cases of injuries is 11. The case fatality rate (%) for injuries is (5/114) × 100 or 4.4%.

What is the crude mortality rate per 100,000 population? From Table 2-6, the total number of deaths is 17 and the total population is 5,837.

The crude mortality rate is (17/5837) × 100,000 or 291.2 per 100,000 population.

sex ratio the number of injuries among men is 73 and the number of injures among women is 41.

The sex ratio for total injuries is 73/41 or 1.78 to 1, male to female

What are the advantages and disadvantages of crude and adjusted rates? What is one of the main purposes of adjusted rates?

a. Crude rate—An advantage of a crude rate is that it permits comparisons of populations that differ in size. An example is the crude death rate, which approximates the proportion of a population that dies during a time period of interest and can be used to compare populations that differ in size, because the standard of comparison is the unit size of populations. The disadvantage of a crude rate is that it has not been modified to take account of any of the factors such as the demographic makeup of the population that may affect the observed rate. b. Adjusted rate—The advantage of an adjusted rate is that it facilitates comparisons of populations that differ in demographic characteristics such as age. One disadvantage of adjusted rates is that calculation of age-adjusted rates is a much more involved procedure than that required for crude rates. The main purpose of adjusted rates is to permit fair comparisons across populations by removing the effect of differences in age other demographic characteristics

Lifetime Prevalence

cases diagnosed at anytime during lifetime

line graph

enables the reader to detect trends in the data

What information is provided with epidemiologic measures?

frequency of disease or condition associations between exposures and health outcomes strength of the relationship between and exposure of health outcomes

case 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.

Ratio

is defined as a fraction in which there is not necessarily any specified relationship between the numerator and denominator.

percentage

is defined as a proportion that has been multiplied by 100. For example: The percentage of male deaths from AIDS was (0.83 × 100) = 83%.

Rate

is defined as a ratio that consists of a numerator and denominator in which time forms part of the denominator. For example: crude death rate= (Number of deaths in a given year/Reference population (during midpoint of the year) × 100,000

Proportion

is defined as a type of ratio in which the numerator is part of the denominator; proportions may be expressed as percentages

Case Fatality Rate

number of deaths due to a disease that occur among persons who are afflicted with that disease.

Incidence

occurrence of disease or mortality within defined period of observation

What is an adjusted rate?

rate of morbidity, mortality in a population in which statistical procedures have been applied to permit of fair comparisons across population by removing effect of differences in the composition of various population.

What are the components of a ratio

rate. proportion, and percentage

Point prevalence

refers to all cases of disease, health condition, or death

Prevalence

refers to all number of existing cases of disease of health condition

sex-specific rate

refers to the frequency of a disease (also mortality) in a gender group divided by the total number of persons within that gender group during a time period times a multiplier. One of the uses of this information is to compare mortality and morbidity between males and females

age-specific rate

refers to the number of cases of disease per age group of the population during a specified time period. Age-specific rates help in making comparisons regarding a cause of morbidity or mortality across age groups

bar chart

shows the frequency of cases for categories of a categorical variable

pie chart

shows the proportion of cases according to several categories