Older Coffee Drinkers May Have the Edge

Summarized by Robert W. Griffith, MD
March 22, 2007

Summary

In people over 65 without high blood pressure, increased caffeine intake is associated with reduced cardiovascular mortality.

Introduction

Whether coffee drinking causes or prevents cardiovascular disease has been a controversial matter. Some studies point one way, some another. Now researchers have suggested the differences may be related to the ages of the subjects studied. Thus elderly people are more likely than younger persons to experience postprandial hypotension - a fall in blood pressure after meals - that shows a relationship with coronary events and mortality. Maybe coffee, which raises blood pressure, could prevent this effect? This hypothesis has been tested in a study done by New York scientists recently published in the American Journal of Clinical Nutrition. Here's a summary of the study.

What was done

Data from the first National Health and Nutrition Examination Study (NHANES I) were used. Participants aged 25 to 74 were surveyed at intervals from 1982 through 1992. Those with a history of cardiovascular disease were excluded.

Beverage consumption at the first follow-up point was based on two questions in a food-frequency questionnaire; the first concerned the number of servings of the beverage usually consumed, and the second was the time during which the beverage was taken. The beverages of interest were ground caffeinated coffee, ground decaffeinated coffee, regular tea, instant caffeinated coffee, instant decaffeinated coffee, herbal tea, and colas. Individual daily caffeine intake was calculated from these answers, using standardized caffeine content for the different drinks. Participants were allocated to one of 4 different categories based on their caffeine intake: less than 30 grams, 30 to 100 grams, 100 to 350 grams, and 350 grams or more per day.

Information on death was confirmed by death certificate or review of medical documentation. Data were collected at the first review point on age, smoking, gender, race, income, physical activity, educational level, alcohol use, body mass index (BMI), and American-style diet intake.

As age was found to be associated with different amounts of caffeine intake, separate analyses were done for participants over and under 65. Similarly, analyses were done for different classes of blood pressure: normal, prehypertension, stage 1 and stage 2 hypertension.

What was found

There were 426 cardiovascular deaths during the 8.8 year follow-up period in the 6,500-odd participants. There was no significant association between caffeine intake and the risk of cardiovascular disease mortality in the participants younger than 65.

In the subjects aged 65 or older, higher intake of caffeine was associated with a lower risk of cardiovascular death, in a dose-related fashion - the more caffeine, the lower the risk. The risk was roughly halved in those drinking four or more servings of caffeinated drinks a day. There was no evidence that decaffeinated drinks provided a protective effect.

The protective effect of caffeine was found in the over-65s with stage 1 hypertension, and in those with prehypertension and with normal blood pressure. However, there was no protective effect in subjects with stage 2 hypertension, or with respect to cerebrovascular mortality, i.e. stroke deaths.

What these findings mean

This was an epidemiological study¹, so that it cannot demonstrate a cause-and-effect between caffeine intake and cardiovascular mortality. But the findings suggest quite strongly that in those over 65 without existing high blood pressure caffeine intake does offer protection from cardiovascular death.

There's a plausible mechanism for this effect, as outlined in the introduction. It may be that the caffeine intake counteracts the postprandial fall in blood pressure (hypotension) in older people, thus reducing the risk for a serious coronary event like a heart attack, and cardiovascular mortality. (This might explain the absence of an effect in people with hypertension.) The study investigators call for more studies to define the possible protective mechanism of caffeine, and to test the concept in a prospective study. In the meantime, they conclude that their study "does not provide a valid basis for recommending increased consumption of caffeinated beverages". However, we believe that, if you like coffee, you don't need to stop drinking it regularly!

Source

• Caffeinated beverage intake and the risk of heart disease in the elderly: a prospective analysis. JA. Greenberg, CC. Dunbar, R. Schnoll ,  et al., Am J Clin Nutr , 2007, vol. 85, pp. 392--398

Footnotes
1. There are different sorts of epidemiological studies. This was a case-control study, in which the frequency of a particular risk factor (or factors) is compared between cases with the disease in question, and people without the disease. Such a study can reveal an association, but not a cause-and-effect relationship. Other epidemiological studies include cross-sectional and cohort studies.

Related Links
The Blood Pressure Villain is Cola, not Caffeine
Is Coffee Good or Bad? - Another Piece of Evidence
There's More to Coffee Than Just Caffeine

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