Question

A population of 9,000 men was examined in January 2014. Of these men, 6,000 were exposed to high levels of air pollution, and 3,000 were exposed to low levels of air pollution. At the physical examination, 90 cases of chronic bronchitis were identified, including 60 cases among the high-exposure group. All of the men who were initially examined and did not have chronic bronchitis were followed by repeat examination over the next five years. These follow-up exams identified 268 new cases of bronchitis in the total group, including 30 cases among the low-exposure group. Calculate the prevalence and the incidence.

Calculate the incidence of chronic bronchitis in the high-exposure group:

Answer 1

The incidence of chronic bronchitis in the high-exposure group is approximately 40.07 cases per 1,000 men over a five-year period, determined by dividing 238 new cases by the 5,940 men initially without chronic bronchitis.

Step-by-step explanation:

To calculate the incidence of chronic bronchitis in the high-exposure group, we first need to determine the number of new cases that appeared during the study period. According to the information provided, there were 60 initial cases amongst the high-exposure group (6,000 men) and an additional 238 new cases (268 new cases in total minus 30 cases from the low-exposure group) over the next five years among those who were initially healthy.

The formula to calculate incidence is the number of new cases divided by the population at risk over a certain time period. The population at risk excludes the initial cases. Therefore, we have 238 new cases divided by 5,940 (6,000 - 60) men, which would yield an incidence rate. To express this as a rate per population, we might want to use a multiplier such as 1,000. The calculation would then be (238 / 5,940) × 1,000.

For the purposes of this example, the calculation yields an incidence rate of approximately 40.07 per 1,000 men over the five-year period in the high-exposure group.