Question

A research team is utilizing data from a large, prospective occupational health cohort of 80,000 industrial workers established in 2010. The original study collected detailed baseline health questionnaires, DNA samples, and environmental exposure logs. The team now hypothesizes that a specific genetic polymorphism increases the risk of developing three distinct conditions: occupational asthma, noise-induced hearing loss, and contact dermatitis. Because genotyping all 80,000 workers is cost-prohibitive, the investigators select a random sample of 3,000 workers from the baseline cohort to undergo genotyping. They also genotype all workers from the entire 80,000-person cohort who developed any of the three incident conditions between 2010 and 2026. The genotype frequencies of the incident cases for each of the three conditions are then separately compared to the genotype frequencies of the initial 3,000-person sample.

Which of the following best describes this epidemiological study design?