Starting to smoke at any age is associated with an increased cancer mortality rate, while quitting, especially at younger ages, can avert most of this risk, according to a research letter published online Oct. 21 in JAMA Oncology.
Blake Thomson, D.Phil., from the American Cancer Society in Atlanta, and colleagues conducted a prospective cohort study to examine the correlation between age at smoking initiation and cessation and cancer mortality at ages 25 to 79 years.
The researchers found 10,014 cancer deaths at ages 25 to 79 years among 410,231 participants with 3.7 million person-years of follow-up. The overall cancer mortality rate ratio associated with current smoking was 3.00 compared with never smokers. The rate ratios were 4.01, 3.57, 3.15, 2.86, and 2.44 for those starting at ages younger than 10, 10 to 14, 15 to 17, 18 to 20, and 21 years or older, respectively. If these excesses were interpreted as mainly causal, smoking would account for 75 and 59 percent of cancer deaths among those starting at younger than 10 years and at age 21 years or older, respectively. Compared with never smokers, the rate ratios were 0.95, 1.23, 1.45, and 1.88 for quitting at ages 15 to 34, 35 to 44, 45 to 54, and 55 to 64 years, respectively, resulting in avoiding an estimated 100, 89, 78, and 56 percent of the excess cancer mortality risk seen in association with continued smoking.
“Widespread smoking cessation among individuals who currently smoke could substantially reduce cancer mortality in the coming years,” Thomson said in a statement.
One author disclosed financial ties to the pharmaceutical industry.
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