A representative sample of U.S. adults was interviewed and examined between 1976 and 1980. Participants were asked about personal characteristics, medical history, current and past medicine use, and health behaviors. Participants' blood pressure was measured carefully, and blood samples were obtained to measure cholesterol levels. Then, from 1976 to 1992, Social Security and National Death Index files were searched to see whether any participants had died and to find causes for death. The researchers then looked at which blood pressure measurements (systolic blood pressure, diastolic blood pressure, or pulse pressure) taken at the first examination predicted deaths. To help ensure correct predictions, they did analyses that “controlled for” other factors, such as age, sex, smoking status, diabetes, and cholesterol level, which might be associated with increased risk for death.