Whitehall I studied 18,000 male civil servants working in London’s 20 departments. There were 10,308 non-manual employees and 7,636 clerical staff. Whitehall II included a further 10,308 male administrative staff. This gave a combined sample size of 15,415. Participants in both phases were 35 to 55 years of age at baseline. All provided details about their work status, as well as lifestyle factors like diet and activity. To identify changes in mortality or health, the follow-up surveys were done every three years for 25 years.
This type of sampling strategy can provide valuable insight into the effects of different factors on various outcomes. These insights can help to prevent future diseases or improve overall health and well-being.