Long-term use of smokeless tobacco : Cardiovascular mortality and risk factors

Sammanfattning: Little is known about the risks of cardiovaseular disease associated with the use of smokeless tobacco, which produces blood nicotine levels similar to those caused by cigarette smoking. There were 900 000 smokeless tobacco users in Sweden in 1996. Epidemiological studies of 136 036 construction workers (6 297 smokeless tobacco users, 28 501 smokers and 32 546 never-users of tobacco), surveyed through 1971-74, regarding the general health profile, blood pressure, sick leaves and disability pensions were conducted together with a 12-year follow-up study of all cause mortality and cardiovascular mortality. Hypertension (blood pressure >160/90) was most common in smokeless tobacco users, particularly after the age of 45 (RR 1.8; 95% c.i. 1.5-2.1). Compared to never-users, respiratory, circulatory, musculoskeletal and mental disorders were slightly more common in smokeless tobacco users, but significantly more common in smokers. During follow-up, smokeless tobacco users, who were middle-aged at the start of follow-up, had a doubled relative risk of dying of cardiovascular disease (RR 2.1; 95% c.i. 1.5-2.9) and smokers had a triple risk (RR 3.2; 95% e.i. 2.6-3.9) eompared with never-users. The risk of dying of eancer was similar in smokeless tobacco users and never-users, whereas smokers showed more than a doubled risk (RR 2.5; 95% c.i. 2.2-3.0). Clinical studies of 151 healthy middle-aged firemen (50 smokeless tobacco users, 33 smokers and 68 non-users) were made to evaluate the influence of long-term smokeless tobacco use on physical performance, cardiovascular metabolic risk factors, ultrasonographic signs of atherosclerosis and diurnal blood pressure variations. Both smokeless tobacco users and smokers had significantly elevated heart rates during the day time (p<0.05) compared with non-users. Daytime diastolic blood pressures were also significantly elevated in both smokeless tobacco users and smokers >45 years of age. The metabolic cardiovascular risk (based on serum lipids, lipoproteins, fibrinogen, PAI-I, insulin and glucose), calculated as the "atherogenic index", was significantly elevated (p<0.001) only in smokers and the 10-year future risk of cardiovascular events (Framingham CHD risk index) was 13.2% in smokers (p<0.001) and 4.6% in smokeless tobacco users (p=0.3) eompared with 3.4% in never-users. Smokeless tobacco users did not exhibit any signifieant signs of accelerated athero sclerosis at ultrasonographic examination of the carotid artery, as did smokers. Smokeless tobacco users did not reveal any significant reduction in maximal physical capacity, whereas the perform ances of smokers were significantly poorer (p<0.001) compared with non-users. It is concluded that the use of smokeless tobacco involves as high exposure to nicotine as smoking, which causes the release of sympathoadrenergic stimuli. This seems to signify an elevated risk of cardiovascular stress involving higher heart rate and blood pressure levels, which might influence the risk of fatal cardiovascular events. However, it does not seem to involve the same high risk of accelerated atherosclerosis as smoking.