Recently Klatsky and associates reported a vast cohort
study of Kaiser Foundation patients and concluded that heavy
coffee intake may increase the risk of coronary artery disease,
reversing their earlier conclusions reported in the
1970s.58 More than 100,000 patients, including 1,914 patients
with coronary disease, admitted between 1978 and
1985 were examined. Patients completed questionnaires
about sociodemographic traits, habits, and health as well as
health measurements and laboratory test results. The median
follow-up was five years. Compared with noncoffee drinkers,
the following relative risks were found: 1.1 for one to
three cups, 1.4 for four to six cups and 1.4 for more than six
cups per day. There was no clear dose-response relationship,
however, and, again, tea consumption was not related to
myocardial infarction or other coronary events. The authors
concluded that a weak, independent correlation of coffee use
to acute myocardial infarction existed, not mediated by an
effect on blood cholesterol levels.58 They recommended that
persons at risk for myocardial infarction should consider limiting
their coffee intake to less than four cups per day.
Another recent large prospective study was reported
by Grobbee and colleagues (The Health Professionals Follow-
up Study)." They examined the risk of myocardial
infarction, the need for bypass grafting or percutaneous angioplasty,
and the risk of stroke in more than 45,589 men.
None of those studied had a history of heart disease. Participants
were mailed questionnaires in 1986, and 33% of the
eligible group responded. No correlation was found between
coronary disease and coffee or caffeine consumption, with
an age-adjusted relative risk for more than four cups per day
of 1.04.
This study has received many criticisms, some criticizing
the 33% response rate to the initial questionnaire. Also, the
authors did not fully explore the more-than-five-cup threshold
that was found by LaCroix and others to be associated
with coronary disease.5559 The study was also criticized for
excluding patients who had coronary disease at the initial
questioning. It may well be that the excluded cohort represented
those who had already suffered from and were sensitive
to the effects ofcoffee or caffeine, as the age ofthe cohort
started at 40 and ended at 75. Also, there was no review of
past habits of coffee consumption. LaCroix's medical student
study"5 suggested a long-term effect (25 years) that
Grobbee and co-workers did not address.
In summary, the evidence to date that coffee or caffeine
intake at normal levels is correlated with coronary heart disease
is inconsistent. The long-term effects of coffee use are
still not clear. The recent work of LaCroix and colleagues
does raise the question of whether coffee drinking produces
effects that may manifest only after several decades. Heavy
caffeine use ( >4 cups per day of coffee) may be associated
with coronary artery disease and needs further investigation.
