By Tim Drake, PharmD, MBA, BCPS, and Martin S. Lipsky, MD

Dr. Drake is Assistant Professor of Pharmacy, College of Pharmacy, Roseman University of Health Sciences. Dr. Lipsky is Chancellor, South Jordan Campus, Roseman University of Health Sciences, South Jordan, UT.

Drs. Drake and Lipsky report no financial relationships relevant to this field of study.

SYNOPSIS: Individuals who smoke fewer than 10 cigarettes per day over their lifetime have a higher risk of mortality than those who have never smoked cigarettes.

SOURCE: Inoue-Choi M, Liao LM, Reyes-Guzman C, et al. Association of long-term, low-intensity smoking with all-cause and cause-specific mortality in the National Institutes of Health-AARP Diet and Health Study. JAMA Intern Med 2017;177:87-95.

Smoking cigarettes continues to be a major health problem around the world. Smoking cessation and awareness programs have led to decreased rates of persons smoking cigarettes and decreased intensity of smoking. However, the number of low-intensity smokers is increasing, and from 2005-2014 the percentage of smokers who only smoke between one and 10 cigarettes per day increased 11% (from 16-27%).1 Although there is a perception that smoking fewer cigarettes is less harmful, the duration of smoking is thought to be a more important contributor to disease risk than the number of cigarettes smoked per day. However, there are little data about the adverse effects from long-term, low-intensity smoking.2

This prospective, cohort study examined 290,215 persons 59-82 years of age participating in the National Institutes of Health-AARP Diet and Health Study between 2004-2005. Historical smoking data were obtained by questionnaire. Patients were followed through the end of 2011.

The primary outcome was all-cause mortality, and secondary outcomes included cause-specific mortality. Hazard ratios (HR) were determined for the primary and secondary endpoints through Cox proportional hazards regression models using age as the time metric and adjusting for sex, race/ethnicity, educational level, physical activity, and alcohol intake. Low-intensity smoking was defined as either less than one cigarette per day (CPD) or 1-10 CPD. The average age of study participants was 71 years, and 57.9% were male. Compared to never-smokers, those who smoked less than one CPD demonstrated a 64% higher risk of mortality, and those who smoked 1-10 CPD demonstrated an 87% increase in mortality (HR, 1.64; 95% confidence interval [CI], 1.07-2.51 and HR, 1.87; 95% CI, 1.64-2.13, respectively). These results were similar when looking at individual causes of mortality with a strong association with lung cancer (HR, 9.12; 95% CI, 2.92-28.47, and HR, 11.61; 95% CI, 8.25-16.35 for less than one and 1-10 CPD, respectively). Additionally, former low-intensity smokers also had a higher risk of mortality compared to never-smokers, but a lower risk compared to those who continue to smoke. Finally, mortality risk increases with increased intensity of smoking.

The study concluded that consistent low-intensity smoking increases the risk of premature mortality compared to those who never smoke.3 There is no “safe” level of cigarette smoking.

COMMENTARY

The 2014 Surgeon General’s report on smoking states that since 1964, more than 20 million premature deaths are attributable to smoking.4 Healthcare practitioners spend time with patients counseling them to quit tobacco. If patients do not quit, many physicians congratulate patients if they reduce the number of cigarettes they smoke per day. After all, it does make sense that a lower dose of a toxic substance should substantially reduce its health-associated risks. However, while it appears that less tobacco use lowers risk, even smoking less than one cigarette per day increases mortality risk by 64% over those who never smoked and also increases the risk of lung cancer. For those smoking 1-10 CPD, cancer risk increases by 12% over those who never smoked. These findings by Inoue-Choi et al highlight the need to advise patients that there is no level of “safe” smoking, and that for patients to optimize their health they need to abstain completely from tobacco. Additionally, if there is an increased mortality risk with the consistent use of even less than one CPD, how many patients get the equivalent of one CPD through second-hand smoke, and what is their relative risk to those with no exposure?

Our guess is that most patients and providers underestimate the risk of low-intensity smoking, and continued education aimed at increasing the awareness of the risk of even low levels of tobacco use is needed for both the public and providers.

REFERENCES

  1. Jamal A, Homa DM, O’Connor E, et al. Current cigarette smoking among adults - United States, 2005-2014. MMWR Morb Mortal Wkly Rep 2015;64:1233-1240.
  2. Flanders WD, Lally CA, Zhu BP, et al. Lung cancer mortality in relation to age, duration of smoking, and daily cigarette consumption: Results from Cancer Prevention Study II. Cancer Res 2003;63:6556-6562.
  3. Inoue-Choi M, Liao LM, Reyes-Guzman C, et al. Association of long-term, low-intensity smoking with all-cause and cause-specific mortality in the National Institutes of Health-AARP Diet and Health Study. JAMA Intern Med 2017;177:87-95.
  4. Centers for Disease Control and Prevention. 2014 Surgeon General’s Report: The Health Consequences of Smoking — 50 Years of Progress. Available at: http://bit.ly/2lrJiwP.