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No safe level of smoking: just one cigarette per day significantly increases mortality risk, study finds

New research highlights the dangers of smoking even for very light smokers. A new study found that people who smoke one or fewer cigarettes per day over a long period still had significantly higher all-cause mortality than non-smokers.

The study on low-intensity smoking looked at mortality rates and causes of death for long-term smokers who smoked either one cigarette or fewer per day, or between one and 10 cigarettes per day. The results showed that consistently smoking one or fewer cigarettes per day was associated with a 64 per cent increase in all-cause mortality, and nine-fold risk of lung cancer, compared to people who never smoked. Consistently smoking between one and 10 cigarettes per day was associated with an 87 per cent increase in all-cause mortality, and a risk of lung cancer almost 12 times as high as a never-smoker.

The good news is that for low-intensity smokers who quit, these risks became progressively lower with younger quitting ages.

The study included 290,215 people, 42 per cent of whom were women. The study subjects were all participants in the National Institutes of Health AARP Diet and Health Study, and completed a lifetime smoking questionnaire in 2004-05, when they were ages 59 to 82. The questionnaire asked whether they smoked, and how much they smoked, during each decade of their lives. Over an average followup period of 6.6 years, there were 37,331 deaths in the group.

The research results suggest that there is no safe level of smoking, and smoking any amount presents a health risk that increases overall mortality risk and risk of death from known smoking-related causes.

The study authors note that most of the people who smoked fewer than 10 cigarettes at the time of the questionnaire had a history of heavier smoking in the past. The numbers who consistently smoked only a few cigarettes per day over their lifetime were low: 159 who smoked less than one cigarette per day over their lifetime, and 1,493 who smoked fewer than 10 per day over their lifetime. The researchers also note that the study was dependent on people's memory for smoking data, which may introduce the possibility of inaccurate recall.

The study, led by Maki-Inoue-Choi, PhD, M.S., at the National Cancer Institute in Rockville, Maryland, was published online in JAMA Internal Medicine on Dec. 5, 2016.

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  • A publication of:
  • Women's College Hospital