At the turn of the twentieth century the average life span was about forty years of age in developed countries. By the beginning of the twenty-first century life spans were nearing eighty years on average.
Of those forty years of increased life span gained during the twentieth century, no more than seven years can be credited to modern medicine, with even most of those due to advances in medical technology rather than drugs. That estimate comes from Dick Jackson, director of the National Center for Environmental Health at the Centers for Disease Control and Prevention.
“Ninety percent of the reduction in the death rate occurred before the introduction of antibiotics or vaccines,” adds Anthony Cortese, a former United States Public Health Service official. “It was largely due to improved water, food, and milk sanitations; a reduction in physical crowding; the introduction of central heating, municipal sewer systems, and refrigeration; and the move away from highly toxic coal and wood burning to less-toxic natural gas and oil.”
The Hundred-Year Lie by Randall Fitzgerald, pg. 143.