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Duration of cigarette smoking confers greater relative risk for CHD than intensity
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CHD risk is greater with lower intensity and longer duration of cigarette smoking compared with higher intensity and shorter duration of smoking, according to data presented in Nicotine & Tobacco Research.
Risk increased with increasing number of pack-years, but among equal pack-years, smoking fewer cigarettes per day over a longer period of time conferred greater CHD risk than smoking more cigarettes per day over a shorter period of time, according to the researchers.
“We now have observed inverse smoking intensity effects in multiple cohorts with differing smoking patterns and other characteristics, suggesting a common underlying phenomenon,” Jay H. Lubin, PhD, of the National Cancer Institute at the NIH, and colleagues wrote.
Researchers applied a relative risk model in pack-years and cigarettes per day, using Poisson regression, to analyze two separate cohorts: the U.S. Agricultural Health Study, a prospective cohort study with 4,396 CHD events over 1,425,976 person-years of follow-up; and the Finnish Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, a double blind, placebo-controlled prevention trial of 29,133 male smokers aged 50 to 69 years, in which there were 5,979 CHD events duirng a follow-up of 486,643 person-years.
In both cohorts, the strength of pack-years association with CHD was dependent upon cigarettes per day (P < .01), Lubin and colleagues found.
The researchers wrote that for adults with 50 pack-years (365,000 total cigarettes), the estimated RR for CHD was 2.1 for those who smoked 20 cigarettes per day and 1.5 for those who smoked 50 cigarettes per day.
“Risk of CHD increases with pack-years of smoking, but accrual intensity strongly influences the strength of the association, such that smoking fewer cigarettes per day for longer duration is more deleterious than smoking more cigarettes per day for shorter duration,” Lubin and colleagues wrote. “This observation offers clues to better understanding biological mechanisms and reinforces the importance of cessation rather than smoking less to reduce CHD risk.” – by Dave Quaile
Disclosure: The researchers report no relevant financial disclosures.
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