Final answer:
The longitudinal study by Doll and Hill focused on the link between smoking and lung cancer, monitoring about 50,000 British male physicians over several decades to understand health outcomes related to lifestyle and risk factors.
Step-by-step explanation:
A longitudinal study involves repeated observations of the same variables over an extended period. The study by Doll and Hill is a classic example, focusing on the connection between smoking and lung cancer. It began with approximately 50,000 British male physicians and spanned over 50 years, with regular updates, including the initial results in 1954 and the last report in 2004. This study, like others, aimed to understand how the health outcomes of individuals vary in relation to lifestyle choices or exposure to certain risk factors.
Studies such as those by Rahe et al. (1967) on life change and illness patterns and the explorations of personality further add to the body of research using longitudinal design. Rosenman et al. (1975) provided another significant contribution with their study on coronary heart disease. Longitudinal research is valuable across various fields as it allows researchers to track changes over time and make robust connections between early-life exposures and later-life health outcomes.