People who consistently smoked an average of less than 1 cigarette per day over their lifetime had a 64% higher risk of earlier death than never-smokers, and those who smoked between 1 and 10 cigarettes a day had an 87% higher risk of earlier death than never-smokers, according to a new study from researchers at the National Cancer Institute (NCI). Risks were lower among former low-intensity smokers than in those who were still smokers, and the risk decreased with an earlier age at quitting. The results of the study were reported in the December 5, 2016, JAMA Internal Medicine.1
Increased Mortality Risks
When researchers looked at specific causes of death among study participants, a particularly strong association was observed for lung cancer mortality. Those who consistently averaged less than 1 cigarette per day over their lifetime had nine times the risk of dying from lung cancer than never-smokers. Among people who smoked between 1 and 10 cigarettes per day, the risk of dying from lung cancer was nearly 12 times higher than that of never-smokers.
The researchers looked at risk of death from respiratory disease, such as emphysema, as well as the risk of death from cardiovascular disease. People who smoked between 1 and 10 cigarettes a day had over 6 times the risk of dying from respiratory diseases than never-smokers and about one and half times the risk of dying of cardiovascular disease than never-smokers.
Diet and Health Study
To better understand the effects of low-intensity smoking on mortality from all causes and for specific causes of death, the scientists analyzed data on over 290,000 adults in the NIH-AARP (American Association of Retired Persons) Diet and Health Study. Low-intensity smoking was defined as 10 or fewer cigarettes per day. All participants were between the ages of 59 and 82 at the start of the study.
Participants were asked about their smoking behaviors during 9 periods of their lives, beginning with before they reached their 15th birthday until after they reached the age of 70 (for the older participants). Among current smokers, 159 reported smoking less than 1 cigarette per day consistently throughout the years that they smoked; nearly 1,500 reported smoking between 1 and 10 cigarettes per day.
Study Limitations
The study relied on people recalling their smoking history over many decades, which introduced a degree of uncertainty into the findings. Also, despite the large number of people surveyed, the number of consistent low-intensity smokers was relatively small.
Another limitation of the study is that the participants were mostly white and in their 60s and 70s, so the smoking patterns collected in the study reflect only a particular set of age groups in the United States. Future studies among younger populations and other racial and ethnic groups are needed, particularly as low-intensity smoking has historically been more common among racial and ethnic minorities in the United States.
Maki Inoue-Choi, PhD
“The results of this study support health warnings that there is no safe level of exposure to tobacco smoke,” said Maki Inoue-Choi, PhD, NCI, Division of Cancer Epidemiology and Genetics, and lead author of the study. “Together, these findings indicate that smoking even a small number of cigarettes per day has substantial negative health effects and provide further evidence that smoking cessation benefits all smokers, regardless of how few cigarettes they smoke.” ■
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