Dr. Rob van Dam and a team from the Harvard School of Public Health and Brigham and Women's Hospital followed 80,000 nurses for more than two decades.
The women kept detailed records of their diet, physical activity, alcohol consumption, weight, smoking and disease history. Over the study period, 8,882 of the women died, including 1,790 from heart disease and 4,527 from cancer.
Some 28 percent of these deaths could have been avoided if the women had never smoked, the researchers said.
And 55 percent of the deaths could have been avoided if the women had never smoked and exercised regularly, eaten a healthy diet low in red meat and trans-fats and maintained a healthy weight, they said.
Smoking played the biggest role in causing premature death, and alcohol consumption played the smallest, they said.