The study of 16 young men who were habitual spit tobacco users measured their responses 30 minutes after dipping snuff.
These readings were compared with measurements from another session involving the same participants after they had used a placebo product that was similar in taste, color and texture but did not contain tobacco or nicotine. The study was randomized and double-blinded; neither the researchers nor the subjects were told when they were taking the placebo and when they were using the tobacco product.
After snuff use, heart rate increased by about 15 beats per minute (25 percent), systolic blood pressure went up by 12 mmHg (10 percent), and measurements of adrenalin in the bloodstream increased by more than 50 percent.
"These results suggest a very significant excitatory effect of substances contained in spit tobacco on the part of the nervous system regulating the heart and blood vessels," says Virend Somers, M.D., Ph.D., the Mayo Clinic cardiologist who led the study. "Although we did anticipate some increase in blood pressure, we were surprised at the magnitude of the increase, as well as the very striking increases in heart rate and plasma epinephrine, or adrenalin. We anticipated that since these individuals were young and healthy and were accustomed to using spit tobacco, that any responses that we measured would be blunted. This makes the degree of increases even more noteworthy."
Robert Wolk, M.D., Ph.D., lead author on this study, noted that these results have implications both for long-term users and for individuals with established heart disease.
"The degree of speeding up of heart rate and increase in blood pressure, as well the increase in adrenalin (epinephrine) levels, suggest that if similar changes occur in people with established heart disease, who use spit tobacco, there may be reason to expect adverse consequences," Dr. Wolk says.
More than five million adults – and more than 750,000 adolescents – use smokeless tobacco in the United States. Snuff use is increasing, especially in young males who participate in athletics. Its cardiovascular effects are not as clear or well understood as those of cigarettes, partly because fewer studies have been done, and partly because many spit tobacco users are relatively young and the bad effects may not be apparent unless use continues for prolonged periods.
By placing electrodes into the sympathetic nerves of the participants, the researchers also obtained a window on the message from the brain to the blood vessels on a moment-by-moment basis.