Improvements in heart disease risk factors can be measured within a few weeks of quitting -- or even reducing -- smoking, according to a new study.

Previous studies have established a link between smoking and heart disease, and smokers are known to reduce their risk by quitting. The sooner they quit the more benefit they see. However, cessation rates still remain within the 15 per cent to 20 percent range.

Many smokers may go through repeated attempts to quit smoking during which they reduce their smoking. Other, more addicted smokers, may be able to cut down on how much they smoke but never quit entirely.

"Alternative treatment approaches, such as smoking reduction, have the potential to benefit those smokers who are not aided by the current strategies of prevention and cessation," says Björn Eliasson, M.D., Ph.D., of Sahlgrenska University Hospital in Sweden. "Despite the availability of effective treatment for more than two decades, smoking cessation remains modest and the global toll of tobacco-related death and disease continues to rise."

The study is published in the August issue of Nicotine & Tobacco Research.

Smoking exposes a person to high levels of carbon monoxide, which has been shown to raise cholesterol levels, white blood cells counts and other risk factors for heart disease. Carbon monoxide also decreases oxygen in the blood, aggravating the complications of heart disease and increasing the risk of heart attack.

The study was based on 33 subjects who were able to quit after four months, during which they progressively reduced their smoking. Those who took part in the study were given nicotine-containing nasal spray to help curb their cravings to smoke.

Just nine weeks into the study, these subjects had reduced their smoking by an average of 50 percent, resulting in a 17 percent reduction in their carbon monoxide levels. This drop in carbon monoxide levels corresponded to significant lessening of heart disease risk factors such as high cholesterol and low blood oxygen capacity.

Even more dramatic improvements in these measures were seen at 17 weeks, when these subjects had quit smoking altogether.

"The clinical benefit of reductions in cigarette consumption can be monitored by measurement of established risk factors, changes which can be used to calculate reduced risk of developing heart disease," says Eliasson.

According to previous research, a decrease of 8 percent to 9 percent in total cholesterol is associated with a significant reduction in the risk of heart disease while a decrease of only 1 percent in low density lipoprotein levels (bad cholesterol) is needed to achieve risk reduction.

Conversely, a 1 percent increase in carbon monoxide levels, as measured in a smoker’s breath, increases the risk of tobacco-related death by 22 percent.

"As understanding of the behavioral stages of change associated with smoking increases, it becomes evident that cessation strategies only assist part of the smoking population. In addition, it has been proposed that successful cessation among less dependent smokers results in a residual population of highly dependent smokers who are unable to stop smoking using the traditional model of abrupt cessation of tobacco use," the researchers say.

The study was funded by Pharmacia Consumer Healthcare, maker of the nasal spray.

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Nicotine & Tobacco Research is the official peer-reviewed quarterly journal of the Society for Research on Nicotine and Tobacco. For information about the journal, contact Gary E. Swan, PhD, at (650) 859-5322.