Smoking declines fail to reduce lung cancer rates, study finds
The prevalence of smoking in Sweden has significantly decreased over the years, yet the incidence of lung cancer remains high. (CREDIT: Creative Commons)
The prevalence of smoking in Sweden has significantly decreased over the years, yet the incidence of lung cancer remains high, particularly among women, according to a recent study conducted at Umeå University.
Professor Bengt Järvholm from the Department of Public Health and Clinical Medicine highlighted the surprising discrepancy between the decline in smoking rates and the expected reduction in lung cancer cases.
"Smoking is undoubtedly the most important risk factor for lung cancer. It is therefore surprising that the decline in smoking is not yet more visible in the statistics. More research is needed to find out why this is the case," Järvholm stated.
Average number of cigarettes sold per year and person over 15 years of age in Sweden between 1940 and 2021. (CREDIT: European Journal of Public Health)
Currently, about five percent of Swedes, both men and women, report daily smoking, a significant drop from the 1960s when approximately half of Swedish men smoked. Although women historically began smoking later than men, the study found that among women, especially those aged 50-69, lung cancer rates have increased.
Previous research has indicated a rapid decline in lung cancer risk following smoking cessation. For instance, a British study revealed a decrease in lung cancer prevalence from 16 percent to three percent among individuals who quit smoking before the age of 50.
The researchers at Umeå University analyzed changes in smoking habits in Sweden from the 1950s and compared them with lung cancer incidence between 1970 and 2021 among individuals aged 40-84. They observed significant variations in lung cancer risk depending on factors such as age, gender, and the type of lung cancer.
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While squamous cell cancer, strongly linked to smoking, saw a decline, adenocarcinoma, another common form of lung cancer, exhibited a six-fold increase. Notably, among women aged 75-79, the risk of squamous cell cancer equaled that of men, highlighting a convergence in smoking-related risks.
Although the study did not offer a definitive explanation for the unexpected trends, several hypotheses were proposed. One possibility is underreporting of smoking habits, which could underestimate the true reduction in smoking prevalence.
Additionally, assumptions regarding the rapid decline in lung cancer risk post-smoking cessation may have been overstated. Furthermore, environmental and lifestyle factors may contribute to lung cancer risk, even among non-smokers, though less frequently.
Incidence rates of all types of lung cancer and squamous cell cancer according to age 1970–2021 (cases per 100 000 persons and year). (CREDIT: European Journal of Public Health)
Despite the concerning findings, Järvholm emphasized the importance of smoking cessation. "The results should certainly not be interpreted as it is useless to quit smoking. On the contrary, the study emphasizes the importance of quitting early, preferably never starting, as it may be the case that the risk of lung cancer is elevated for longer than we previously thought," he stressed.
According to the study, if the risk of developing lung cancer in 2021 mirrored that of 1970 among individuals aged 40-84, there would have been a decrease of 555 cases among men, while women would have seen an increase of 1,637 cases.
Incidence rates of all types of adenocarcinoma cancer and other cancer cell types according to age 1970–2021 (cases per 100 000 persons and year). (CREDIT: European Journal of Public Health)
The study utilized data from the National Board of Health and Welfare's cancer registry, cross-referenced with tobacco smoking statistics from surveys and cigarette sales records.
How does smoking affect your body?
According to the Cleveland Clinic, tobacco use harms every organ in your body. Smoking tobacco introduces not only nicotine but also more than 5,000 chemicals, including numerous carcinogens (cancer-causing chemicals), into your lungs, blood and organs.
The damage caused by smoking can shorten your lifespan significantly. In fact, smoking is the number one cause of preventable death in the United States.
Pregnant women who smoke put their unborn babies at risk, too. Possible effects on pregnancy include:
Ectopic pregnancy, a life-threatening condition when the embryo implants outside the uterus.
Miscarriages.
Stillbirths.
Birth defects, such as cleft palate.
Low birth weight.
What other conditions may be caused or worsened by tobacco?
In addition to its known cancer risks, the Cleveland Clinic states that smoking causes many other chronic (long-term) health problems that need ongoing care. Specific smoking-related problems that need treatment include:
Decreased HDL (good) cholesterol and increased blood pressure (increasing risks for heart attack and stroke).
Erectile dysfunction.
Lower oxygen to the heart and other tissues in the body (increasing risks for coronary artery disease, peripheral artery disease, and diabetes).
More frequent routine illnesses like colds, especially in children living with smokers.
Poorer lung function (ability to get enough oxygen) leading to COPD, asthma, bronchitis, or emphysema.
The study is titled, “Changing smoking habits and the occurrence of lung cancer in Sweden—a population analysis" is published in the European Journal of Public Health.
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