Credit: NPG

Smoking is bad for one's health. The habit increases the risk of cardiovascular disease, including ischaemic heart disease and stroke, as well as other conditions, such as cancer. The investigators of two studies published in the New England Journal of Medicine quantified smoking-associated mortality in the USA and came to similar conclusions: the risk of death is currently approximately three times higher in smokers than in nonsmokers, and much of the elevated risk is attributable to cardiovascular disease.

One study examined temporal trends in mortality by comparing Cancer Prevention Study (CPS) I and II data from the 1960s and 1980s, respectively, with pooled data from five contemporary cohort studies. Smokers' relative risk of all-cause mortality increased over time, ranging from 1.35 (95% CI 1.30–1.40) in women and 1.76 (95% CI 1.71–1.81) in men from the CPS I cohort, to 2.76 (95% CI 2.69–2.84) in women and 2.80 (95% CI 2.72–2.88) in men from the contemporary cohort. Although cigarette consumption peaked a decade later for women than it did for men, both sexes now have similar smoking consumption patterns (e.g. daily consumption and age at initiation), and the overall risks associated with smoking are now similar for men and women.

With regard to cardiovascular disease, the data indicate that the relative risk of death from ischaemic heart disease rose from 1.56 and 1.69 in women and men, respectively, in the 1960s to 2.86 and 2.50, respectively, in contemporary times. Similarly, the relative risk of death from other types of heart disease was 1.20 and 1.51, respectively, in the 1960s, and 1.84 and 2.15, respectively, in the period 2000–2010. The relative risk of death from stroke rose from 1.51 and 1.38, respectively, in the 1960s CPS I cohort to 2.10 and 1.92, respectively, in the contemporary cohort.

In the other study published in the same journal, 113,752 women and 88,496 men aged ≥25 years, interviewed in the period 1997–2004 as part of the U.S. National Health Interview Survey, were classified as current smokers, former smokers (quit ≥5 years before death), or nonsmokers. Smoking shortened life expectancy by 10 years and was associated with a three-fold increase in all-cause mortality (HR 3.0 for women, 99% CI 2.7–3.3; HR 2.8 for men, 99% CI 2.4–3.1). Increases in ischaemic heart disease (HR 3.5 for women, 99% CI 2.7–4.6; HR 3.2 for men, 99% CI 2.5–4.1), stroke (HR 3.2 for women, 99% CI 2.2–4.7; HR 1.7 for men, 99% CI 1.0–2.8), and other vascular diseases (HR 3.1 for women, 99% CI 2.2–4.4; HR 2.1 for men, 99% CI 1.5–3.0) paralleled the increases seen in all-cause mortality.

Notably, smoking cessation was found to improve outcomes substantially in both studies. In the latter study, individuals who quit smoking aged 25–34 years, 35–44 years, 45–54 years, or 55–64 years regained about 10, 9, 6, and 4 years of life, respectively. Survival curves for nonsmokers and people who quit before the age of 35 years were nearly identical. These data indicate that it is never too late to quit.

Smoking cessation programmes have met with varied success. Fear is a powerful motivator, and smokers who are hospitalized for an acute myocardial infarction (AMI) might be particularly motivated to quit. AMIs can provide “teachable moments, when patients and their families are motivated to make lifestyle changes that will reduce their chance of having a recurrent heart attack,” says Mark Eisenberg, lead author on a new paper in the Journal of the American College of Cardiology. Dr Eisenberg and colleagues assessed a pharmacological intervention for smoking cessation in patients hospitalized with AMI. Eisenberg says he decided to conduct the study “because we are very effective at giving other types of medications at the time of a patient's heart attack”.

The investigators examined the safety and efficacy of bupropion, an antidepressant shown to improve cessation rates in other patient groups, in 392 patients randomly assigned to receive either bupropion or placebo. The drug was first administered during a patient's hospital stay and, although bupropion was well tolerated and safe, two-thirds of patients from both the bupropion and the placebo groups returned to smoking within 12 months of their AMI. Although he was disappointed with the results, Eisenberg points out that the rate of cessation was higher in both groups than in many studies of young, healthy smokers. Furthermore, many people who returned to smoking smoked less than they did before their AMI. “This is good clinically and may indicate a population that can be retargeted for antismoking efforts. It often takes multiple quit attempts before patients are ultimately successful,” he says. Eisenberg tells us that the EVITA trial, which has a similar study design, but assesses varenicline, is currently underway.

“Smoking cessation is probably the most important thing a smoker with AMI can do to improve future health,” say Neal L. Benowitz and Judith J. Prochaska in an editorial that accompanies the article in the Journal of the American College of Cardiology. They highlight the importance of intensive counselling both in hospital and after discharge for all smokers, and not just those who indicate a readiness to quit.