Thomas Royle Dawber, 92, who transformed the medical world's understanding of heart disease as the first director of the Framingham Heart Study, one of the most important research projects of the 20th century, died Nov. 23 at a care center in Naples, Fla. He had Alzheimer's disease.

The study, which Dr. Dawber led from 1949 to 1966, found links between vascular diseases -- the leading cause of death in the United States -- and diet, blood pressure, obesity, exercise and smoking. Its findings form the basis for now-common medical advice: Eat more fiber, fresh fruit, vegetables and fish and less fat, and get regular exercise.

Dr. Dawber coined the term "risk factor," a concept later applied to cancer, arthritis and other diseases. His landmark scientific paper in 1961 isolated the major factors associated with heart disease: high blood pressure, high cholesterol levels and certain irregularities in the electrical patterns in the heart. The paper also noted hints of a connection between smoking and heart disease.

Framingham researchers have subsequently published nearly 1,300 scientific papers that have illuminated the connection between heart disease and diabetes, and they have expanded their research into osteoporosis and eye and lung diseases.

When it began in 1948, the study pioneered the notion that detailed observation of the lifestyle, behavior and medical conditions of healthy individuals would help doctors figure out what causes heart disease. Previous studies had looked only at those who were already ill. In addition, it was one of the few studies to include women -- not out of any sense of evenhandedness, but because researchers noticed that women seemed less likely to develop heart disease than men and they wanted to find out why.

It wasn't easy at first to persuade 5,209 healthy Framingham residents between the ages of 30 and 60 to participate in the study. New Englanders were leery of disclosing private medical information, although they liked the idea of getting thorough medical checkups for free. William P. Castelli, who became director of the study in 1979, recalled Dr. Dawber training new researchers in bedside techniques.

"He would say that these people are doing you a favor by letting you examine them, so don't ever lose an opportunity to thank them. That kind of interaction is enough to change the way you talk to patients for the rest of your life," Castelli told U.S. News and World Report in 1998.

William B. Kannell, who was director of the study from 1966 to 1979, said Dr. Dawber insisted that appointments be kept on time, procedures be thoroughly explained and results be promptly reported to the volunteers and their primary physicians. Most of the original heart study participants have died, but their children and grandchildren now are in the study.

"One of the achievements of the study was that it was able to maintain a very good follow-up record, losing only 3 percent of the population after all these years," Kannell said. Dr. Dawber also encouraged investigators to pursue intriguing ideas, even when it went against commonly accepted medical beliefs. "He was open to new ideas, which led to much of the productivity of the study. Dawber was willing to let us stick our necks out."

Dr. Dawber also played a key role in saving the study in 1968, when the federal government considered shutting it down. Aided by the thousands of volunteers who had willingly submitted to pokes and prods for years, Dr. Dawber led a campaign that raised more than $500,000 to save the study and arranged a partnership between the study and Boston University, where he was director of the preventive medicine program.

Dr. Dawber was born in Duncan, British Columbia, and graduated from Haverford College in Pennsylvania. He earned a medical degree from Harvard University in 1937 and immediately joined the U.S. Public Health Service, where he served on the medical staff on Coast Guard cutters. During World War II, he was chief of medicine for the Marine Hospital in Boston.

The Public Health Service established the Framingham Heart Study in 1948, and the surgeon general named Dr. Dawber its first director the next year. He retired from Boston University in 1980 and moved to Naples.

Survivors include a daughter, Dr. Nancy Dawber of Naples; a son, John Dawber of Needham, Mass.; and two grandchildren.