There Really Is No Safe Level of Smoke Exposure

Abstract & commentary

By Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington. Dr. Phillips is a consultant to Cephalon and Ventus and serves on the speakers bureaus of Cephalon and Boehringer Ingelheim.

Synopsis: Even in people who had never smoked cigarettes, pipe and cigar smoking was associated with decreased lung function and increased odds of airflow obstruction.

Source: Rodriguez J, et al. The association of pipe and cigar use with cotinine levels, lung function, and airflow obstruction: A cross-sectional study. Ann Intern Med 2010;152:201-210.

As cigarette smoking has decreased (from a prevalence of 33% in 1983 to 19.8% in 2007), pipe and cigar smoking have substantially increased in the United States in recent years. These authors set out to determine whether pipe and cigar smoking results in biological absorption of tobacco smoke, and to test the hypotheses that pipe smoking or cigar smoking is associated with impaired pulmonary function. To accomplish this, they did a secondary analysis of the MESA (Multi-Ethnic Study of Atherosclerosis) cohort.

In brief, MESA is a longitudinal study of more than 6000 men and women aged 45-84 years from 6 U.S. communities.1 People excluded from participation in MESA included those with clinical cardiovascular disease, body weight > 300 lbs, pregnancy, or impediment to long-term participation.

MESA participants underwent extensive assessment of a variety of lifestyle and medical factors, including age, sex, race or ethnicity, educational attainment, medical history, occupational exposure to dust, fumes, or smoke, environmental tobacco smoke exposure, and family history of emphysema. They also underwent extensive baseline testing of cardiovascular risk factors. Along the way, they had pulmonary function testing, had urinary cotinine measured, and were queried about smoking behaviors. Smoking was assessed by means of the American Thoracic Society questionnaire.2 Pack-years of cigarette smoking were calculated in a standard way. For pipe smoking, participants were first asked, "Have you smoked at least 20 pipe-bowls in your lifetime?" If they answered "yes," additional questions included, "How old were you when you first started smoking pipes?" "On average, about how many pipe-bowls a day do/did you smoke?" "Have you smoked a pipe within the last 30 days?" and, if relevant, "How old were you when you quit smoking?" "Cigar-years" were calculated as the self-reported age of starting to the age of quitting (or current age if participants still smoked) multiplied by the number of cigars per day.

After elimination of data from those who had exclusion criteria or who had restrictive lung disease, the authors had 3528 participants whose data could be used to perform the analysis. Their mean age was 66 years, 49% were male, 35% were non-Hispanic white, 26% were African American, 22% were Hispanic, and 17% were Chinese American. Nine percent reported ever smoking pipes, but most of these had quit. Eleven percent reported ever smoking cigars, and about one-fifth of these was still smoking cigars at the time of analysis. Fifty-two percent reported ever smoking cigarettes, and 9% were current cigarette smokers. Of 484 participants with a history of pipe or cigar smoking, 88% also reported a history of cigarette smoking. Participants with a history of pipe or cigar smoking were more likely to be male, to be white or African American, and to have higher educational attainment.

The odds ratio for airflow obstruction was approximately doubled among participants who smoked pipes or cigars only compared with never-smokers, but was even greater among participants who smoked pipes or cigars in addition to cigarettes. The reduction in pulmonary function was modest and not statistically significant in the 56 participants who smoked pipes or cigars only, but (as expected) was greater and statistically significant in the much larger group who smoked cigarettes only, and was greatest of all in those who smoked pipes or cigars in addition to cigarettes.

In the entire sample, the number of pipe-years of smoking was inversely associated with FEV1. When the analysis was restricted to those who had smoked pipes but who had never smoked cigarettes, effect estimates were of larger magnitude, but were no longer statistically significant. The decrease in lung function from pipe smoking was much larger in pipe smokers who smoked heavily (most of whom were white and male). The mean FEV1 in the 64 participants with 50 or more pipe-years was 154 mL lower than that of participants who had never smoked pipes, and the mean FEV1:FVC ratio was 2.1 percentage points lower (P = 0.039). With regard to cigar smoking, more cigar-years were associated with greater decreases in FEV1 and FEV1:FVC ratio, and increased odds ratio for airflow obstruction. As expected, the number of cigarette pack-years was inversely associated with FEV1 in the entire sample in fully adjusted models. Cotinine levels were less than 10 ng/mL in never-smokers, 43 ng/mL in current cigar smokers, 1324 ng/mL in current pipe smokers, and 4304 ng/mL in current cigarette smokers.

The authors concluded, "Pipe and cigar smoking increased urine cotinine levels and was associated with decreased lung function and increased odds of airflow obstruction, even in participants who had never smoked cigarettes."

Commentary

Significant progress has been made in reduction of cigarette smoking in the United States. This change has been the result of much effort by many people, and has resulted from a combination of education, fiscal policy (e.g., increased excise taxes), and advocacy. Unfortunately, other kinds of tobacco use have actually increased during the same time period. Smoking of all types of cigars increased by nearly 50% from 1993 to 1997, and pipe and cigar tobacco smoking increased by 28% and 8%, respectively, from 2002 to 2006. In 2006, the prevalence of pipe and cigar smoking in the United States was 1% and 6%, respectively.3,4

The health effects of both active and passive cigarette smoking are well known. Cigarette smoking is the main cause of COPD and lung cancer, and is the fourth leading cause of death in the United States.5 Much less is known about the health effects of pipe and cigar smoking. Two large cohort studies have suggested that pipe and cigar smoking are associated with an increased risk of hospitalization and death,6,7 but these studies had methodologic problems. The current report is the first U.S. study to investigate the possible effects of cumulative pipe and cigar smoking on lung function. And the new isn't good. The evidence presented here indicates that the use of these forms of tobacco increases the risk of obstructive airway disease, and there is measurable absorption of nicotine in pipe and cigar smokers. Smoking is just not good for you.

References

1. Bild DE, et al. Multi-ethnic study of atherosclerosis: Objectives and design. Am J Epidemiol 2002;156: 871-881.

2. Ferris BG. Epidemiology Standardization Project (American Thoracic Society). Am Rev Respir Dis 1978;118(6 Pt 2):1-120.

3. Substance Abuse and Mental Health Services Administration. Results from the 2006 National Survey on Drug Use and Health: National Findings. Rockville, MD: Office of Applied Studies; 2007. NSDUH Series H-32, DHHS Publication No. SMA 07-4293.

4. Tager IB, et al. The natural history of forced expiratory volumes. Effect of cigarette smoking and respiratory symptoms. Am Rev Respir Dis 1988;138:837-849.

5. Hoyert DL, et al. Death: Final Data for 1999. Hyattsville, MD: National Center for Health Statistics; 2001. DHHS Publication No. PHS 2001-1120.

6. Henley SJ, et al. Association between exclusive pipe smoking and mortality from cancer and other diseases. J Natl Cancer Inst 2004;96:853-861.

7. Iribarren C, et al. Effect of cigar smoking on the risk of cardiovascular disease, chronic obstructive pulmonary disease, and cancer in men. N Engl J Med 1999;340: 1773-1780.