Analyzing Disease Frequency
Order Instructions:
Analyzing Disease Frequency
When epidemiologists measure disease frequency, they analyze the incidence and prevalence of a disease. Incidence is the number of new cases of a disease in a particular population during a specific time period. This measure is useful when public health officials and epidemiologists are looking at the first occurrence of a disease. It is also important when comparing populations to determine disease risk.
For each problem, answer the following questions:
Name the appropriate measure of disease frequency that should be used in each scenario and justify its use (why that particular measure is the appropriate one).
The percentage of elderly men who are diagnosed with prostate cancer by age 80.
The number of mothers who die during the first year after giving birth due to complications from the birthing process.
On the last day of the school year, the number of freshman college students who are at least 15 pounds heavier than when they started the school year.
Calculate the appropriate disease frequency rate. Show your work.
The cumulative incidence rate in a population of 100,000 people where 9 new cases of disease were reported within 1 year.
The prevalence of a chronic disease on November 1st where 9 initial cases were found in September with an additional 45 cases reported in October of a small city with a population of 75,000 people.
The relative risk of death from exposure A if the mortality rate in the exposed group is 60 deaths per 1000 person-years and the mortality rate in the unexposed group is 20 per 1000 person-years.
The prevalence of a health condition is the existing number of cases of that condition in the population. State whether the factors listed below are likely to increase or decrease the prevalence of a health condition and Explain your reasoning.
Improvements in diagnostic criteria
Shorter duration of a health condition
Decrease in the incidence of the health condition
Loss of healthy people from the population for other reasons.
SAMPLE ANSWER
Disease Frequency
The appropriate measure of disease frequency
Part 1: Percentage of elderly men: The apt measure is gender and age specific proportion of persons who are affected. Gender and Age is the appropriate measure since the problem is prostate cancer that develops only in males and the age that has been indicated in this specific case is 80 years.
Part 2: For the number of mothers who die in the initial year after they have given birth because of complications from the birthing process, the apt measure of disease frequency is Attributable Proportion amongst the women who are exposed. This is the apt measure given that the exposure in this case is women who are expectant who pass away in the first 12 months after procreating and they have developed problems as a result of the process of giving birth.
Part 3: The apt measure is Attributable Proportion amongst the total population. In this situation, the freshman students who increased weight within a time period of 12 months are taken out of total freshman college students. It is of note that the total number of freshman students at the college comprised the denominator.
Calculation of the appropriate rate of disease frequency
Part 1: Cumulative incidence rate within a population of 100,000 persons in which nine new cases of illness were reported in one year. Cumulative incidence is understood as a measure of the occurrence of new cases of the health condition within the population (Kleinbaum, 2013). Cumulative incidence rate (R) in this problem is the proportion between new cases of the disease of interest and the individuals who are at risk. The denominator refers to the size (N) of the population that is not affected, while the numerator is understood as the number of newly affected people (A).
R = New cases (A) ÷ People at risk (N)
Thus in this problem, the cumulative incidence rate will be (9 ÷ 100,000) x 100% = 0.009%
Part 2: Prevalence (P) basically signifies the proportion of a given population which has the illness of interest at a given time, for instance on a particular day. To estimate this value, the number of cases or of existing people who are affected (C), is divided by the total number people within the population (N).
Prevalence (P) = Cases (C) / Number of People (N)
In this situation, the Prevalence (P) of a chronic illness on 1st November is 9 cases of the month of September plus 45 cases reported in the month of October (C) divide by (/) total number of people (N) which is 75,000
P = ? C = 54, N = 75,000
P = (54 ÷ 75,000) x 100% = 0.072%
Part 3: the relative risk of death from exposure A
Relative Risk (RR) or Risk Ratio is understood as the ratio of the occurrence of the death or disease amongst the people who are exposed and the occurrence amongst those persons who are not exposed (Bonita, 2009).
RR = occurrence amongst those exposed ÷ occurrence amongst unexposed
In this situation, the occurrence is 20/1,000 amongst those unexposed and 60/1,000 amongst those exposed. RR is thus 60 ÷ 20 = 3. What this implies is that the risk of death in the exposed group is 3 times greater than in the unexposed group.
Prevalence of a health condition
- Improvements in diagnostic criteria – likely to increase
When diagnostic criteria is improved, positive value will be increased. Therefore, diagnosis of the disease is carried out correctly and appropriate treatment is started. This will consequently lead to control of the health condition and in so doing decreases the number of cases as well as prevalence (Noordzij, 2010).
- Shorter duration of a health condition – likely to decrease
It is possible to have shorter duration of a health condition in either of 2 instances. First is where recuperation is very fast and it is no longer a case; and secondly where the likelihood of death from the health condition is extremely high and those who are affected with the illness face the threat of dying. In either of these 2 cases, the prevalence would reduce considering that prevalence is basically the number of old and new cases that exist at a given instance.
- Decrease in the incidence of the health condition – likely to decrease
If there is a decrease in incidence, there will also be a decrease in prevalence given that prevalence is the product of duration of the disease and incidence.
- Loss of healthy people from the population for other reasons – likely to increase
This will certainly increase the prevalence of the disease since the loss of healthy persons basically means an increased proportion of persons who are at risk of getting the health condition. More number of persons who are at risk signifies that more persons are affected by the disease leading to a rise in the number of patients, thus increasing the prevalence of the health condition (Kleinbaum, 2013).
References
Bonita, R. (2009). Basic Epidemiology. Cambridge, MA: Penguin Publishers.
Kleinbaum, D. G. (2013). Measures of Disease Frequency. New York City, NY: Springer Publishers.
Noordzij, M. (2010). Measures of Disease Frequency: Prevalence and Incidence. National Center for Biotechnology Information.
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