Key Point

Health benefits, including a longer life, can be achieved only by complete smoking cessation—not by cutting back.

OSLO—New Year’s resolutions may not always come to fruition, but those who vow to give up smoking and find that they cannot quit completely may seek comfort in the logic, "I'm smoking fewer cigarettes, so I must be healthier." However, researchers have produced a study contending that only halving the number of cigarettes smoked daily will not reduce a smoker’s risk for an early death.¹

Norwegian public health officials Aage Tverdal, PhD, and Kjell Bjartveit, MD, PhD, MPH, analyzed data from 51,210 men and women with baseline cardiovascular screenings conducted during the 1970s and spanning 13 years, during which details of cigarette consumption and duration of smoking were collected as well-known risk factors for cardiovascular disease. They also followed up on causes of death in participants with the National Register through 2003.

The participants were categorized into six groups based on their cigarette consumption pattern over the years: never smokers; ex-smokers (who used to smoke daily but quit before baseline examination); quitters (smoked daily at baseline, but had completely quit by the last examination); reducers (smoked 15 or more cigarettes daily at baseline, but reported consumption of at least 50% less by the last examination); moderate smokers (smoked less than 15 cigarettes at baseline and still smoked daily); and heavy smokers (smoked 15 or more cigarettes at baseline and could not be categorized as a reducer or quitter by the final examination).

Compared to smoking rates at baseline, male reducers lowered their daily cigarette consumption by 58%, and female reducers lowered consumption by 56%. By the last examination, cigarette consumption was slightly decreased in heavy smokers and slightly increased by moderate smokers of both sexes.

NO COMPROMISES WITH DEATH

Despite the strong reduction rates seen in the study cohort, Drs. Tverdal and Bjartveit found that reducers had almost the same adjusted relative risk for death from any cause as did heavy smokers; relative risk for death from cardiovascular or ischemic heart disease was not significantly lowered, either. Only quitters, ex-smokers, and never smokers significantly reduced their risk of all-cause mortality, by 53%, 63%, and 66%, respectively.

Men who halved their daily cigarette consumption reduced their rate of death from lung and other smoking-related cancers, but not significantly (reduced smoker relative risk: 0.72 for smoking-related cancers, 0.71 for lung cancer). Women who cut back reduced their relative risk for lung cancer death by 49%, however overall death rates and smoking-related cancer death rates actually increased by 11% and 40%, respectively. The drastic reversal of relative risk rate was unanticipated, and the authors admitted that they had no explanation for the surprise finding other than chance.

In addition to a lack of all-cause death rate reduction, reduced smokers had a lower stature and a higher frequency of disability pension than heavy smokers. Background characteristics including blood pressure, physical activity, and body mass index did not differ significantly between reducers and heavy smokers. The authors noted, "A change in cigarette consumption does not go together with a change in lifestyle factors beneficial to health."

To guard against the possibility of underreporting of cigarette consumption, the researchers measured patient serum thiocyanate levels, which are a practical indicator of tobacco smoke exposure in the past couple weeks. Levels were found to be appropriately lower in reduced smokers than in heavy smokers, leading the authors to conclude, "A substantial proportion of their reduction in consumption has been real, although its health consequences are largely unchanged."

A CHANGE IN PHYSICIAN ADVICE

The authors recommend that physicians rethink their last-resort plea to patients: "If you are unable to quit, cut down," which they claim is widespread advice. They admit that reduction in consumption has its place as a temporary stopgap in the road to quitting; however, many patients see it as an acceptable permanent solution. The authors raised the possibility that this belief offers people false hope.

"The study proves quite clearly the only safe way out of the risk caused by smoking: people who quit smoking have achieved a risk level that is remarkably lower than in those who continued to smoke," concluded the investigators.

—Jessica Dziedzic

Reference
1. Tverdal A, Bjartveit K. Health consequences of reduced daily cigarette consumption. Tobacco Control. 2006;15:472-480.

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