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What relationship does prevalence have with the duration of a disease?
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Prevalence is influenced by both the incidence and the duration of the disease. Longer duration increases prevalence, while shorter duration decreases it.
How is prevalence defined in epidemiology?
Prevalence is the number of affected persons in the population divided by the number of all persons in the population at a specific point in time.
Describe an example where changes in treatment outcomes can significantly alter the prevalence of a disease.
For chronic diseases like coronary heart disease (CHD), improved treatment and care (such as in Hollywood) can lower death rates and extend the duration of illness, leading to higher prevalence compared to areas with poorer healthcare outcomes (like the Bronx).
Give an example to illustrate how incidence and prevalence differ in TB cases.
Incidence for TB would be the number of new TB cases each month, while prevalence would include all the TB cases at a specific time, accounting for those who are still sick, cured, or deceased.
How do higher cure rates affect the prevalence of a disease?
Higher cure rates decrease prevalence as more people are removed from the total pool of affected cases.
What is the formula for calculating prevalence?
Prevalence = (Total number of cases at a specific time / Total population) * 1000.
Why might a population with better healthcare have a higher prevalence of a chronic disease like CHD?
Better healthcare in a population can lead to longer survival with the disease, thereby increasing its prevalence due to a longer duration of illness.
In an example where 5 people develop tuberculosis (TB) over 6 months, what would the prevalence account for?
The prevalence accounts for the total number of TB cases each month, including those who remain sick, are cured, or die.
What is the main difference between incidence and prevalence?
Incidence measures new cases over time, while prevalence measures total cases at a specific point in time.
What is the definition of incidence in epidemiology?
Incidence is the number of new cases of a disease during a specific time period divided by the number of persons at risk during the same period.
What happens to prevalence if there is an increase in the incidence of a disease?
Prevalence goes up as there are more new cases adding to the total number of affected persons.
Why must everyone in the denominator of an incidence calculation have the potential to become part of the numerator?
Because the denominator must include only those at risk of developing the disease to accurately measure the rate of new cases.
If a population has higher death rates for a disease, how does this affect prevalence?
Higher death rates decrease the prevalence as more individuals are removed from the pool of affected persons.
Explain the impact of incidence and duration on the prevalence of a disease.
Prevalence is directly proportional to the incidence of new cases and the duration of the disease. Higher incidence or longer duration increases prevalence, while lower incidence or shorter duration decreases it.
How do you calculate the incidence rate per 1000 population?
Incidence rate per 1000 population is calculated by (number of new cases / number of persons at risk) * 1000.
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