Clinical Briefs: Spilling the Beans (Coffee and Vascular Health)

With Comments from Russell H. Greenfield, MD

Dr. Greenfield is Medical Director, Carolinas Integrative Health, Carolinas HealthCare System, Charlotte, NC, and Clinical Assistant Professor, School of Medicine, University of North Carolina, Chapel Hill, NC.

Source: Vlachopoulos C, et al. Chronic coffee consumption has a detrimental effect on aortic stiffness and wave reflections. Am J Clin Nutr 2005;81:1307-1312.

Goal: To assess the effect of chronic coffee ingestion on aortic stiffness and wave reflections.

Study Design: Cross-sectional study performed in Athens, Greece.

Subjects: Two hundred twenty-eight clinically healthy participants (141 men).

Methods: Coffee consumption (all types, including “Greek” and espresso) over the previous year was ascertained using a food-frequency questionnaire and classified in the following manner: low (< 200 mL/d), moderate (200-450 mL/d), and high (> 450 mL/d) intake. Subjects were studied in the morning after fasting overnight. Blood pressure was determined and aortic elastic properties were then assessed by measuring the carotid-femoral pulse wave velocity (PWV), augmented pressure (AP), augmentation index (AIx), and Dt.

Results: Fifty-four percent of participants reported moderate-to-high consumption of coffee, with men consuming more coffee on average than women. A linear significant relationship was established between level of coffee consumption and arterial pressures as well as indices of arterial function, with the high-consumption group having significantly higher arterial pressures, and values for PWV, AIx, AP, and Dt. The difference between aortic and peripheral pulse pressure values relative to coffee intake was also significant, suggesting that coffee consumption has a greater effect on aortic pulse pressure, but this latter finding was also associated with variables such as smoking habits, body mass index, and blood lipids.

Conclusion: Chronic coffee consumption has a detrimental effect on aortic stiffness in healthy subjects, which may increase the risk for cardiovascular disease (CVD).

Study strengths: Multiple linear regression analysis for numerous variables.

Study weaknesses: Limitations associated with food-frequency questionnaire/ recall; only assessed otherwise healthy individuals.

Of note: One cup of coffee (150 mL) was held to contain 80 mg of caffeine; consumption of decaffeinated coffee, tea, caffeine-containing soft drinks, and chocolate were included in the analysis; none of the subjects reportedly used medications that contained caffeine; carotid-femoral PWV is an established index of aortic stiffness; the waveform generated within an artery is the sum of the forward traveling waveform (generated by pump action) and the backward traveling “echo” reflected at a peripheral site (the merging of incident and reflected waves appears as an inflection point where early and late systole divide); AP represents the maximum systolic pressure minus the pressure at the inflection point; high AIx values can indicate increased wave reflection due to increased arterial stiffness; Dt represents the time from the beginning of the waveform to the inflection point, and also reflects arterial stiffness; the more coffee participants ingested on aver- age the more likely there was to be a significant history of smoking; the majority of participants were at least slightly overweight.

We knew that: Large artery stiffness and wave reflections are independent predictors of CVD risk (determine left ventricular function and coronary blood flow); the pulse wave travels at higher speed in a stiff blood vessel; the pathophysiologic manifestations of increased aortic stiffness and wave reflections include elevated systolic blood pressure, increased pulse pressure, and decreased diastolic blood pressure; data on the effects of coffee intake on CVD risk remain contradictory, but caffeine has previously been shown to acutely increase aortic stiffness and wave reflection, and to acutely increase blood pressure; chronic coffee ingestion has been associated with higher levels of inflammatory markers.

Comments: This paper lends additional evidence to that of other studies addressing the potential downside of coffee/caffeine ingestion that have appeared in this newsletter. Far be it for the editors of this periodical to assault one’s right to wake up to the smell of fresh coffee (more likely to wake up as a result of fresh coffee!), but the amount of data pointing to potential consequences of both acute and chronic caffeine ingestion are compelling. Additionally, patients with high intakes of coffee/caffeine appear more likely to have other factors that place them at higher risk for CVD, including tobacco use, dyslipidemia, and being overweight. It may well be time for all of us to go to sleep earlier rather than make up for sleep deprivation with a stop at the local coffee shop before work.

What to do with this article: Keep a copy of the abstract on your computer (to review with your morning green tea).