The sooner you kick your bad habits, the less severe the long-term damage will be. That is the conclusion reached by several studies that have attempted to estimate when a smoker must quit so that their long-term risks are the same as “never smokers.” The latest of these investigations, published in the Jama Network Open journal, collected data from more than half a million people in the United States. Based on this data, it estimates that people who quit smoking before the age of 35 have a similar long-term mortality risk to people who have never smoked. After that age – although giving up tobacco will always yield benefits – former smokers are at a disadvantage compared to people who never smoked. As the authors explain, stopping smoking before the age of 45 is associated with a 90% drop in the excess risk of mortality compared with those who continue to smoke. For those who stop smoking before the age of 64, the figure is 66%.
The investigation, which studied data among adults aged 25 to 84 from 1997 to 2018, found that among the white population, smokers have three times the mortality rate of people who have never smoked. Among the Black and Hispanic community, the mortality rate is double. The authors, led by Blake Thompson of the American Cancer Society in Georgia, calculate that “if one were to assume that the associations in this report are causal, then more than 40% of deaths among ever smokers in this study and more than 60% of deaths among current smokers were attributable to smoking.” Among the main risks that would be reduced are deaths from cancer or from cardiovascular or respiratory disease.
The results are comparable to those of similar studies that have tried to estimate the reversible damage caused by tobacco based on when a person quits. A study conducted with more than a million women in the United Kingdom and published in The Lancet calculated that quitting smoking before the age of 40 reduced the risk of death associated with tobacco by 90%; the figure rose to practically 100% if it was done before the age of 30.
Joan Soriano, a scientist at Madrid’s Health Research Institute at Princesa Hospital, explains that smoking is harmful to health for many reasons: when a person smokes they inhale nicotine and 4,000 other substances. When someone quits smoking, they are no longer exposed to these substances, and therefore, the direct harm of nicotine, acute inflammation, the build up of heavy metals and oncotoxic materials, as well as the shortening of telomeres. Exploring how these mechanisms are initiated and reversed “is very important, but very difficult,” acknowledges Soriano, who points out that the latest research “does not explore the mechanisms, but rather the consequences of smoking and the benefits of quitting.” It’s important to underscore, he says, that the damage begins with the very first cigarette and compounds over the years. However, “the good news is that the damage is not irreversible and that quitting is easier and more beneficial today than tomorrow, because the benefits begin a few days after quitting smoking,” says Soriano.
But the experts make it clear that this does not mean that young people should not smoke on the belief that they can reverse the damage later by quitting, as there are health consequences for all ages. According to Esteve Fernández, director of the Tobacco Control Unit of the Catalan Institute of Oncology, the research shows that quitting smoking at any age has a positive impact on health. “Some factors are quickly noticeable, such as stopping coughing, but also in a year the risk of heart attack is reduced by half, something that may not be noticed directly.”
Quitting is also beneficial for people who have other health problems. “Some doctors won’t tell cancer patients to stop smoking because they already have the disease, but we know that when a patient with any disease [quits smoking], the risk of surgery lowers, because smoking impairs healing. For example, radiotherapy, doesn’t work as well, because the irrigation of the tissues is worse,” says Fernández, who is also a professor of public health at the University of Barcelona.