Cohort Study Calculations and Explanations

This document presents the analysis of a cohort study investigating the relationship between working at the Bethlehem Asbestos Company and the risk of developing lung disease among men attending Frederick Douglas High School in West Baltimore. Study Data and Relative Risk CalculationThe study tracked a cohort of 300 men, divided into two groups:Exposed Group (Worked in Asbestos Company): 100 men, 35 of whom developed lung disease1.Unexposed Group (Did Not Work in Asbestos Company): 200 men, 20 of whom developed lung disease2222.1. 2x2 Table SummaryLung DiseaseNo Lung DiseaseTotalExposed (Worked in Company)35 (A) [cite: 2804]65 (B) [cite: 2805]100 (A+B) [cite: 2806]Unexposed (Did Not Work)20 (C) [cite: 2810]180 (D) [cite: 2811]200 (C+D) [cite: 2812]Total55 [cite: 2813]245 [cite: 2814]300 [cite: 2815]2. Relative Risk (RR) CalculationRelative Risk (RR) measures the risk of the outcome (lung disease) in the exposed group relative to the unexposed group3.Risk (Exposed): $text{Risk for Exposed} = text{A} / (text{A} + text{B}) = 35 / 100 = mathbf{0.35}$ 4Risk (Unexposed): $text{Risk for Unexposed} = text{C} / (text{C} + text{D}) = 20 / 200 = mathbf{0.1}$ 5Relative Risk (RR): $text{RR} = 0.35 / 0.1 = mathbf{3.5}$ 6Conclusion: Exposure to asbestos increases the risk of getting lung disease by 3.5 times7. Risk in Percentages and Clinical Meaning3. Percentage RiskRisk for Exposed (Asbestos Exposure): $35 / 100 times 100 = mathbf{35%}$8888.Risk for Unexposed (No Asbestos Exposure): $20 / 200 times 100 = mathbf{10%}$9999.4. Clinical Epidemiological MeaningThe $10%$ base risk for the unexposed group indicates that all individuals are at risk for developing lung disease10. This is the background risk.The risk difference (or attributable risk) is $35% - 10% = mathbf{25%}$111111. This means that asbestos exposure increases the chance of developing lung disease by an additional 25%12. Asbestos exposure did not cause all the risk of lung disease because a 10% chance already existed13. Explanation of Relative Risk (RR) ValuesThe value of the Relative Risk (RR) indicates the relationship between exposure and outcome:RR = 1: Indicates no difference in risk between the exposed and unexposed groups. The exposure (or lack thereof) does not impact the population14.RR 1: Suggests that the exposure negatively affects the population. The exposure increases the risk of the outcome (e.g., lung disease)15.RR 1: Indicates that the exposure has positive protective factors on the population, meaning the exposed group has better outcomes or a reduced risk of the outcome16.