Findings from a 50-year study into the dangers of smoking showed that if
people quit by the age of 30 they can avoid nearly all of the risk of dying
prematurely.
"Cigarette smoking reduces the expectation of life by 10 years," said
91-year-old Oxford University Professor Richard Doll who discovered the link
between cancer and smoking.
"It is clear that consistent cigarette smoking doubles mortality throughout
adult life -- middle and old age. It is also clear that giving up smoking can
eliminate a very large part of the hazard," he told Reuters.
Doll and Bradford Hill confirmed the link between smoking and lung cancer in
a landmark study published in the British Medical Journal on June 26, 1954.
Half a century later, Doll and Oxford University Professor Richard Peto
report the 50-year results from the same study of 34,439 British doctors in the
journal.
"This study is a remarkable achievement. Studies that last 50 years are
highly unusual in medicine, and it's even more unusual for one to have an author
who was there at the beginning and after 50 years," the journal's editor Dr
Richard Smith told a news conference.
"It has taught us a great deal," he added.
Doll, who had smoked for 19 years before giving up, had planned only a
five-year project but the initial findings were so intriguing he carried on for
five decades.
"I gave up smoking at age 37 when I saw the results of our first study. They
were quite convincing to me," he said in an interview.
The early results from his second study confirmed that smoking causes lung
cancer and suggested that it also causes heart disease.
"We thought we'd better carry the study on for a lot longer and see if
smoking causes anything else and by goodness it does," said Doll.
"By the time we did the 40-year follow-up...we found there were some 25
diseases which smoking seemed to cause and that the mortality was about double
with the consistency of smoking."
Fifty-year results showed that among men born in the 1920s who became
persistent smokers, about two-thirds died from their habit.
"Nobody has ever before seen a population in which two-thirds of the smokers
get killed by their habit," said Peto, who has worked with Doll for 30 years.
"These men who were born in the 1920s and went into the army in the Second
World War...became serious cigarette smokers from the age of 18 in a way no
previous generation had ever done. Among those who continued, about two thirds
got killed by it."
Since Doll began the study five decades ago, tobacco has already killed about
100 million people worldwide. During the present century there will be about one
billion tobacco deaths if current smoking patterns continue, according to Peto.
"Smoking kills people and stopping works," he said.
