What is the sampling frame for each phase of the Whitehall study (Whitehall I and II)?

The sampling frame for the Whitehall I study was a cohort of 18,000 male civil servants from 20 London-based departments. The participants consisted of 10,308 clerical workers and 7,636 non-manual staff. For the Whitehall II study an additional sample of 10,308 female administrative staff were recruited to give a total sample size of 15,415 for both genders. All participants in both phases were aged between 35 and 55 at baseline and provided information on their employment status along with lifestyle factors such as diet and physical activity levels. Furthermore, follow up surveys were conducted every 3 years over the course of 25 years to identify any changes in health or mortality rates over time.

Overall, by using this type of sampling strategy researchers can gain valuable insights into how different environmental or behavioral factors may contribute to various outcomes which can be beneficial for preventing future illnesses or improving overall well-being among populations.