By purchasing this content you agree and accept the terms and conditions
R.S. Paffenbarger, Jr. and W.L. Haskell are with the Standford University School of Medicine. I-M. Lee and Paffenbarger are with the Harvard School of Public Health. J.N. Morris is with the London School of Hygiene and Tropical Medicine. P.D. Thompson is with the University of Connecticut Medical Center and Hartford Hospital. Lee is with Harvard Medical School.