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Cancer patients nearly double their risk of heart attack, stroke or death due to cardiovascular disease compared with non-smokers if they carry on smoking after diagnosis.
The research, published in European Heart Journal, found that compared with sustained non-smoking, the risk of cardiovascular events during follow up was 86%, 51% and 20% higher among continuing smokers, initiators/relapsers and quitters, respectively.
The findings were consistent for women and men, and when the risk of myocardial infarction, stroke and cardiovascular death were analysed separately.
Study author Dr Hyeok-Hee Lee of Yonsei University College of Medicine, Seoul, Korea said: “A cancer diagnosis is an extremely stressful life event, which often leads to significant changes in a person’s lifestyle. Smoking, in particular, is a health-related behaviour that can be heavily influenced by mental distress.
“However, little was known about the relationship between changes in smoking habits after a cancer diagnosis and the risk of cardiovascular disease—the leading cause of non-cancer-related death among cancer survivors.”
Smoking cessation and cardiovascular events
The researchers analysed data from a Korean national health claims database. The study included 309,095 cancer survivors who had never had a myocardial infarction or stroke. Patients were divided into four groups based on their change in smoking habits after receiving a cancer diagnosis: (1) sustained non-smokers, (2) quitters, (3) initiators/relapsers and (4) continuing smokers.
Of the 309,095 cancer survivors, 250,102 (80.9%) sustained non-smoking, 31,121 (10.1%) quit smoking, 4,777 (1.5%) initiated or relapsed to smoking, and 23,095 (7.5%) continued smoking after being diagnosed with cancer. The proportion of initiators/relapsers and continuing smokers combined was highest in survivors of urinary tract cancer and lowest among breast cancer survivors.
The researchers assessed the risk of cardiovascular events (myocardial infarction, stroke or death due to cardiovascular disease) for each group during a median of 5.5 years. The analyses were adjusted for characteristics that could influence the association between smoking and cardiovascular events including age, sex, household income, residential area, alcohol, physical activity, body mass index, blood pressure, blood glucose, cholesterol level, number of other medical conditions, medications, cancer type and anti-cancer treatments.
The benefits of quitting were even higher when compared with continuing to smoke. Of those who were smokers before being diagnosed with cancer, 57% quit after finding out they had cancer. Smoking cessation was associated with a 36% reduction in the risk of cardiovascular events compared with continued smoking.
Dr. Lee added: “Our results reinforce the existing evidence on the well-known cardiovascular risks of tobacco smoking and emphasise the benefits of smoking cessation, even for cancer survivors. Additionally, the finding that over 40% of patients who had been smoking before their cancer diagnosis continued to smoke afterwards highlights the need for more robust efforts to promote smoking cessation among cancer survivors, who already have an elevated risk of cardiovascular disease compared to their peers.”
