Examkin

Question

Difficulty: HardMeasures of Disease Frequency and Association

A prospective cohort study is conducted to evaluate the association between a severe sedentary lifestyle and the development of peripheral artery disease (PAD). The study enrolls 10,000 middle-aged adults without preexisting cardiovascular disease. At baseline, researchers identify that 2,500 participants meet the criteria for a severe sedentary lifestyle. Over a 10-year follow-up period, 250 of the participants with a severe sedentary lifestyle develop PAD. During the same period, 150 of the remaining participants develop PAD.

Based on these findings, what percentage of the overall PAD incidence in this study population is directly attributable to a severe sedentary lifestyle? (Provide your answer as a numerical percentage).

Answer: 50 %

Answer

50
The correct response is 50. The question asks for the percentage of the overall disease burden attributable to the risk factor, which is the Population Attributable Risk Percent (PARP). PARP is calculated as Itotal−IunexposedItotal\frac{I_{\text{total}} - I_{\text{unexposed}}}{I_{\text{total}}}. The total incidence (ItotalI_{\text{total}}) is the total number of cases (250+150=400250 + 150 = 400) divided by the total population (10,00010,000), which equals 0.040.04. The unexposed incidence (IunexposedI_{\text{unexposed}}) is the number of cases in the unexposed group (150150) divided by the number of unexposed individuals (10,000−2,500=7,50010,000 - 2,500 = 7,500), which equals 0.020.02. Plugging these into the formula yields 0.04−0.020.04=0.020.04=0.50\frac{0.04 - 0.02}{0.04} = \frac{0.02}{0.04} = 0.50, or 50%.

Step-by-Step Solution

1
Determine the specific epidemiological metric requested by the question stem.
The metric required is Population Attributable Risk Percent (PARP).
The question asks for the percentage of the 'overall PAD incidence in this study population' that is attributable to the risk factor, rather than just the disease in the exposed individuals.
2
Calculate the incidence of the disease in the unexposed group (IunexposedI_{\text{unexposed}}).
Iunexposed=1507,500=0.02I_{\text{unexposed}} = \frac{150}{7,500} = 0.02 (2%).
This establishes the baseline risk of developing PAD without the severe sedentary lifestyle, which is needed to find the excess risk in the population.
3
Calculate the incidence of the disease in the total population (ItotalI_{\text{total}}).
Itotal=40010,000=0.04I_{\text{total}} = \frac{400}{10,000} = 0.04 (4%).
This is the denominator for the PARP formula, representing the overall burden of disease in the cohort.
4
Calculate the Population Attributable Risk Percent (PARP).
PARP=0.04−0.020.04×100=50%PARP = \frac{0.04 - 0.02}{0.04} \times 100 = 50\%.
PARP is defined as (Itotal−Iunexposed)/Itotal(I_{\text{total}} - I_{\text{unexposed}}) / I_{\text{total}}, yielding the proportion of total disease burden directly linked to the exposure.

Key Concept

Population Attributable Risk Percent (PARP) measures the proportion of the incidence of a disease in the total population (exposed and unexposed combined) that is due to the exposure.
Rate this question

Topics

Measures of Disease Frequency and Association

More questions from this topic