Whitehall I sampled 18,000 civil servants of London’s 20 departments. Participants were 10,308 non-manual and 7,636 manual clerical staff. The Whitehall II study recruited an extra sample of 10,308 women administrative staff to bring the total number of participants for both sexes up to 15,415 At baseline, all participants were between the ages of 35-55 and gave information about their lifestyles such as eating habits and levels of physical activity. Moreover, the survey was conducted three times a year for 25 years in order to track any change over time.
This type of sample strategy can provide valuable insight into the impact that different behavioral or environmental factors can have on various outcomes. These insights can help to prevent future illness or improve overall health amongst populations.