It was also found that women who quit before 40 dropped their risk
of premature death by 90 percent, and women
who quit before 30 dropped their risk
by 97 percent. Even women who quit at about 50 years old avoid at least two-thirds of ongoing smokers' excess mortality. Peto says that the bottom line is that quitting smoking before middle age will add an average of 10 years of life back.
Cigarette smoking accounts for about 443,000 deaths each year in the U.S.