Story highlights More than half of current smokers report having started smoking before they were 18

Raising the legal age to buy tobacco could dramatically reduce future smoking prevalence, report says

Raising it to 21 or 25 could result in a quarter-million fewer premature deaths, it says

(CNN) The public health benefits of barring people under age 21 from buying cigarettes could be tremendous, including "4.2 million fewer years of life lost" among the next generation of American adults, according to a report released this week by the Institute of Medicine.

Setting the minimum age at 21 nationwide, the report estimates, would result in nearly a quarter-million fewer premature deaths and 50,000 fewer deaths from lung cancer among people born between 2000 and 2019.

The study, conducted at the request of the U.S. Food and Drug Administration, compared the predicted benefits of raising the minimum legal age for buying tobacco products -- currently 18 in most states -- to 19, 21, and 25 years. It concludes that the greatest benefits would arise if the legal age nationwide were 25, at which point the prevalence of smokers among today's teens, when they become adults, would decline by 16%.

Predicted smoking prevalence falls an estimated 12% with the minimum age set at 21, and only 3% if set at 19, according to the report, titled "Public Health Implications of Raising the Minimum Age of Legal Access to Tobacco Products."

Even though fewer teenagers are using tobacco than ever before, more than half of current smokers say they started smoking before they were 18, according to the report.

Read More