No Safe Level for Smoking

People who consistently smoked an average of less than one cigarette per day over their lifetime had a 64% higher risk of earlier death than the never smokers, and those who smoked between one and 10 cigarettes a day had an 87% higher risk of earlier death, according to a new study from researchers at the US National Cancer Institute (NCI).  

Risks were lower among former low-intensity smokers compared to those who were still smokers, and risk fell with earlier age at quitting. The results of the study were reported early December, in JAMA Internal Medicine.

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 one cigarette per day over their lifetime had nine times the risk of dying from lung cancer than never smokers. Among people who smoked between one and 10 cigarettes per day, the risk of dying from lung cancer was nearly 12 times higher, nih.gov reported.

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 one and 10 cigarettes a day had over six 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.

Smoking has many harmful effects on health, which have been detailed in numerous studies since decades. The health effects of consistent low-intensity smoking, however, have not been well studied and many smokers believe that low-intensity smoking does not affect their health.

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. Low-intensity smoking was defined as 10 or fewer cigarettes per day. All participants were age 59 to age 82.

Participants were asked about their smoking behaviors during nine periods across 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 one cigarette per day consistently throughout the years that they smoked; nearly 1,500 reported smoking between one and 10 cigarettes per day.

 “The results of this study support health warnings that there is no safe level of exposure to tobacco smoke,” said Maki Inoue-Choi, Ph.D., 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.”