Framingham Heart Study
This paper is a very fascinating history and totally worth a read. Almost everything on this page is distilled from it. Here’s the chief architect’s obituary which has a precis of the study.
Original Cohort
- Recruited between 1948 and 1952 and consisted of 5209 residents aged 28 to 62 years, half women.
- Hypertension systolic blood pressure ≥160/95.
- Framingham because they were (a) nearby and (b) had a racial and socioeconomic composition that was thought to reflect “America” during the 1940s1.
”Risk Factor” and Scores
First study to use the term “risk factor”2. Amazing.
The articulation of the risk factor concept laid the foundation for the development of clinical risk scores. The first attempt to create a multivariable risk function for coronary heart disease in Framingham was published by Truett, Cornfield, and Kannel in 1967.48 Prior to that, the typical approach to considering multiple risk factors simultaneously was “multiple cross-classification,” which involved creating tables with cells corresponding to combinations of the risk factors. Unfortunately, with more than a few variables, thousands of cells would be needed. The authors proposed a multivariable logistic models with 7 risk factors: age, total cholesterol, weight, ECG abnormality, hemoglobin, cigarettes smoked, and systolic blood pressure. Individuals in the top decile compared with the lowest decile had a thirty-fold (men) to seventy-fold (women) difference in the incidence of coronary heart disease.
Average risks are measured with the number of individuals at risk
for the outcome at the beginning of follow-up as the denominator,
whereas incidence rates have the amount of person-time contributed
by these individuals as the denominator.
Can you explain incidence in terms of “open population” or “dynamic population?”