Smoking and coffee often go together. But the combination appears to have a harmful effect on arteries and blood flow that is greater than would be expected from simply combining the effects of each practice. The negative effects are both immediate and long-term, according to a new study in the Nov. 2, 2004 issue of the Journal of the American College of Cardiology.
“This is the first study to investigate the combined effect of smoking and caffeine on the stiffness of large arteries such as the aorta and the load that is imposed on the heart,” said Charalambos Vlachopoulos, M.D., at the Athens Medical School and Hippokration Hospital in Athens, Greece. “Our study confirms that smoking has an additional unfavorable effect and that heavy coffee consumption may pose an additional risk. According to our study, for individuals who have not yet quit smoking, it is advisable not to smoke while consuming coffee or other caffeine-containing beverages, as very frequently is the case. A healthy heart may be able to compensate, at least in the short run, for such unfavorable conditions, but for patients with impaired cardiac function these effects may be deleterious,” said Dr. Vlachopoulos.
This research had two parts: an acute study of the immediate effects of smoking and caffeine and a population study that looked for signs of long-term consequences. In each study, the researchers evaluated the stiffness of the aorta (the largest artery leading from the heart) and reflection waves in arterial blood flow. Each of these factors is an indication of cardiovascular disease risk. They are considered key components in the development of systolic hypertension, which is the type of high blood pressure that often develops in older people.
In the acute study, aortic stiffness was studied in 14 apparently healthy smokers and wave reflections were studied in 10 smokers. By measuring pulse wave velocity (a higher velocity indicates stiffer arteries) and the augmentation index (which measures pulse waves bouncing back to the heart), the researchers found that when smoking followed caffeine intake, the negative effect was greater than the sum of the effects of smoking and caffeine intake at separate times.
The population study enrolled 160 healthy participants who were categorized into three groups: coffee drinkers who smoked (66 men and 31 women), coffee drinkers who did not smoke (20 men and 21 women), and those who neither drank coffee nor smoked (10 men and 10 women). Measurements made following an overnight fast showed a significant interaction of chronic coffee consumption and smoking with pulse wave velocity and augmentation index.
“Some of our previous studies, together with some from other laboratories, have shown that smoking and caffeine separately increase arterial stiffness. However, it was not known whether the impact of one or the other stimulus was so large that it did not leave room for further deterioration. In other words, when I smoke a cigarette, do my arteries harden so much that when I drink coffee at the same time they cannot stiffen anymore, and vice versa? Particularly in the acute study, the final impact of the two stimuli was larger than the sum of the separate impacts of the two stimuli alone,” Dr. Vlachopoulos said.
Dr. Vlachopoulos noted that this study involved healthy participants, so the researchers cannot say with certainty whether smoking and caffeine have the same effects in people with cardiovascular disease.
“As regards the mechanism in the acute setting, this most likely has to do with the effect of smoking and caffeine on catecholamines (norepinephrine, epinephrine and dopamine) and adenosine (a substance that dilates arteries). In the chronic setting, the explanation is not so straightforward, mainly because the possible effects of chronic coffee consumption on the arterial wall have not been investigated at a basic level,” Dr. Vlachopoulos said.
Krishnankutty Sudhir, M.D., F.A.C.C., at Stanford University in California, who was not connected with this research, said he was impressed by the study method that looked at both immediate and long-term effects.
“Another reason I like the paper is that it looks at a combination of two common habits in our society,” Dr. Sudhir said. “The study has not shown that coffee per se is bad, so I wouldn’t want people to make that interpretation, but it does show that if you are a smoker, drinking coffee can have hazardous effects on large blood vessels.”
Hector O. Ventura, M.D., F.A.C.C., at the Ochsner Clinic in New Orleans, who also was not connected with this research, said this view of the effects of coffee and cigarettes together is new.
“What they found is that when you combine cigarette smoking and coffee together, they have a synergistic effect on blood pressure, which I don’t think has been described before,” Dr. Ventura said. “I think it’s very strong, the way this study has been done.”
Dr. Ventura added that the results suggest arterial stiffness and blood pressure may help explain part of the mechanism by which smoking and caffeine increase the risk of cardiovascular disease.
The American College of Cardiology, a 31,000-member nonprofit professional medical society and teaching institution, is dedicated to fostering optimal cardiovascular care and disease prevention through professional education, promotion of research, leadership in the development of standards and guidelines, and the formulation of health care policy.