1. Caroline Bedell Thomas, a 1930 school of medicine graduate, became the school’s third female full professor in 1970.
2. Study participants were 1,337 Johns Hopkins medical students who graduated between 1948 and 1964, with a median age of 24.6 at the start of the study.
3. In 2017, 570 participants filled out the survey, 83 were no longer participating and 684 had died. Of the 120 women in the original cohort, 42 are alive now. The median participant age is now 86, with the youngest 78 and the oldest 101.
4. The response rate has remained roughly steady, between 75 and 80 percent. Participants are in every state, with about 20 living abroad. At least one family sends a newsy holiday letter each year. “We will keep following this cohort until the last participant stops responding,” says epidemiologist Alden Gross, who relies on the study for his research into cognitive decline. Researchers telephone family members to gather information after participants die or can no longer respond.
5. The study has yielded 169 published papers to date, including Thomas’ 1956 blockbuster in the American Journal of Medical Science, which for the first time suggested a link between cholesterol and heart disease.
6. The Precursors Study was the first of its kind and served as a model for subsequent longitudinal investigations, including the well-known Framingham Heart and Harvard Physicians’ Health studies.
7. Precursors Study participants are, by definition, highly educated, and nearly all are wealthy, white and male. Though they don’t represent society as a whole, the group’s conformity has its advantages for researchers who have fewer variables to consider. Professor John Thomas of the historically black Meharry Medical College in Nashville, Tennessee, worked with Caroline Bedell Thomas to develop a similar study, collecting data on eight classes of its students between 1958 and 1965. Studies comparing the two cohorts have found important results, including a 60 percent higher risk of dying from cardiovascular disease among the Meharry doctors.
8. The Precursors Study was likely the first to use Rorschach tests in a consistent way, and is today almost certainly the largest repository of the famed inkblot tests ever administered and analyzed in a standardized fashion, says Gross. The tests were developed in 1918, and Thomas learned about them from Paul Lemkau, the 1941 founder of the division of mental hygiene at Johns Hopkins. She used them to measure aggression, anxiety and other characteristics, and over time linked those tendencies to health consequences such as a greater risk for cancer or suicide.
9. Perhaps the studies using Precursors data that now get the most attention examine how doctors plan for and think about their own deaths. Several investigations, including some helmed by current Precursors Study Director Joseph Gallo, use the surveys to show significant gaps between the aggressive end-of-life treatments doctors recommend for their patients, and their own desire to avoid a similar level of intervention for themselves.