[Homeroast] Coffee Associated With Lower Risk of Arrhythmias

Dean De Crisce decrisce.md at gmail.com
Mon Mar 15 12:21:10 CDT 2010

Coffee Associated With Lower Risk of Arrhythmias

Michael O'Riordan

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March 9, 2010 (San Francisco, California) — Good news for coffee
drinkers--new observational data presented last week at *EPI|PNAM 2010*, the
*Cardiovascular Disease Epidemiology and Prevention* and *Nutrition,
Physical Activity, and Metabolism 2010 Conference*, suggests that multiple
cups of Joe are associated with a lower risk of arrhythmias. [1]

"A lot of people think they have palpitations from coffee, and doctors
commonly tell people not to drink it, but there are very few actual data,
and the data that are available suggest no relationship," said lead
investigator *Dr Arthur Klatsky* (Kaiser Permanente Division of Research,
Oakland, CA). "We went into this study thinking there would be no
association, but to our surprise, there was actually an inverse
relationship. It could be protective, although one observational study
doesn't prove anything yet."

To *heartwire *, Klatsky said his group has studied coffee off and on for
many years and has published several studies, which have tended to vary in
their results. These studies suggested a slightly increased risk of fatal
and nonfatal MI, mostly in smokers, and no overall effect of coffee drinking
on total mortality or cardiovascular mortality.

With these inconclusive findings, Klatsky said his group decided to look at
some of the other major causes of cardiovascular disease, such as
arrhythmias. They studied 130 054 participants in the Kaiser Permanente
health plan, all of whom completed a questionnaire on coffee intake and
other health habits.

After adjusting for multiple variables, including body-mass index, blood
pressure, total cholesterol, and other measurements, the researchers found
that coffee consumption was associated with a lower risk of hospitalization
for arrhythmias and that the protective effect appeared to be additive.
Individuals who drank more than four cups of coffee per day had an 18% lower
risk of being hospitalized for any arrhythmia, and this reduction in risk
was consistent among men and women, different ethnic groups, and smokers and

*Relative Risk (95% CI) of Arrhythmia Diagnosed by Coffee Intake*
  *Arrhythmia* *<1 cup/d* *1–3 cups/d* *>4 cups/d*  *All arrhythmia* 0.97
(0.85–1.11) 0.93 (0.84-1.02) 0.82 (0.73–0.93) *Paroxysmal supraventricular
tachycardia* 0.85 (0.54–1.34) 1.01 (0.72–1.40) 0.63 (0.41–0.98) *Paroxysmal
ventricular tachycardia* 0.99 (0.59–1.63) 1.04 (0.71–1.53) 1.22 (0.79–1.87)
*Atrial fibrillation* 0.82 (0.67–1.00) 0.88 (0.76–1.01) 0.81
(0.69–0.96) *Atrial
flutter* 0.99 (0.65–1.93) 0.86 (0.62–1.20) 0.80 (0.54–1.19) *Premature beats
* 1.98 (1.02–3.84) 0.98 (0.54–1.79) 0.62 (0.28–1.35) *SA node dysfunction* 1.04
(0.71–1.52) 0.90 (0.67–1.21) 0.88 (0.62–1.24) *Other arrhythmia* 1.02
(0.79–1.32) 0.93 (0.77–1.14) 0.72 (0.56–0.93)

Klatsky said that coffee is a complex substance and that it includes other
ingredients that might be at work, including antioxidants, in reducing the
risk of arrhythmias. However, they also performed an analysis looking at the
relative reductions in risk among people who drank only decaffeinated coffee
and found no protective effect, which suggests caffeine is the protective

*Unknown Mechanisms*

The mechanisms are still unknown at this stage, but Klatsky said that
caffeine competes with adenosine in brain, so it might also compete with
adenosine in the heart. Because adenosine affects conduction and recovery of
heart muscle cells after depolarization, one of those effects, particularly
the shortening of the refractory period, could provoke rhythm problems. By
drinking coffee, the researchers speculate that this adverse effect is

The data are observational and need to be confirmed in other studies.
Moreover, the end point includes hospitalizations for arrhythmias, an end
point that is easy to document, but future studies examining rhythm
disturbances should include arrhythmias not severe enough for the patient to
warrant a trip to the hospital, according to the researchers.

With the possibility of coffee protecting the heart and at minimum showing
no risk of harm, Klatsky said it is possible for the popular drink to be
tested in a randomized, controlled clinical trial, although the kinks of
that study would need to be worked out.

"It might be a little tricky to get people to give up their coffee, and for
those who aren't coffee drinkers, it might be tough to get them to start
drinking four cups per day," said Klatsky

Dean D

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