Adults who quit smoking significantly reduced their risk for mortality from pneumonia; the risk decreased even more with added years of not smoking, according to data from nearly 95,000 individuals.
Smoking is associated with an increased risk for pneumonia, but the extent to which smoking cessation reduces this risk long-term has not been explored, wrote Tomomi Kihara, MD, PhD, of the University of Tsukuba, Japan, and colleagues on behalf of the Japan Collaborative Cohort.
In the Japan Collaborative Cohort Study for Evaluation of Cancer Risk study, known as the JACC Study, a community-based cohort of 110,585 individuals aged 40-79 years participated in health screening exams and self-administered questionnaires that included information about smoking. Other findings from the study have been previously published.
In the current study, published in Preventive Medicine, the researchers reviewed data from 94,972 JACC participants who provided data about smoking status, including 59,514 never-smokers, 10,554 former smokers, and 24,904 current smokers. The mean age of the participants was 57 years; 57% were women.
The respondents were divided into groups based on years of smoking cessation: 0-1 year, 2-4 years, 5-9 years, 10-14 years, and 15 or more years. The primary endpoint was an underlying cause of death from pneumonia.
Over a median follow-up period of 19 years, 1806 participants (1115 men and 691 women) died of pneumonia.
In a multivariate analysis, the hazard ratio (HR) for those who quit smoking compared with current smokers was 1.02 for 0-1 year of smoking cessation, 0.92 for 2-4 years, 0.95 for 5-9 years, 0.71 for 10-14 years, and 0.63 (0.48-0.83) for 15 or more years. The HR for never smokers was 0.50. The analysis adjusted for competing risk for death without pneumonia in the study population.
Most of the benefits of smoking cessation occurred after 10-14 years, the researchers wrote in their discussion of the findings, and smoking cessation of 10 years or more resulted in risk for death from pneumonia similar to that of never-smokers.
“To our knowledge, no previous studies have examined the association between years of smoking cessation and pneumonia in a general population,” they added.
The study findings were limited by several factors, including the use of data on smoking and smoking cessation at baseline as well as a lack of data on the use of tobacco products other than cigarettes, although alternative tobacco products are rarely used in Japan, the researchers noted. Other limitations include the use of pneumonia mortality as an endpoint, which could have ignored the impact of smoking cessation on less severe pneumonia, and the inability to clarify the association between smoking cessation and pneumonia mortality by sex because of the small number of female former smokers. However, the results were strengthened by the large sample size and long observation period, they said.
“The present study provides empirical evidence that smoking cessation may lead to a decline in the risk of mortality from pneumonia,” and supports smoking cessation as a preventive measure, the researchers concluded.
The study was supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology; Ministry of Health, Labour and Welfare, Health and Labor Sciences; and an Intramural Research Fund for Cardiovascular Diseases of National Cerebral and Cardiovascular Center. The researchers had no financial conflicts to disclose.
Prev Med. August 9, 2022. Abstract
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