Drinking at least one cup of coffee daily may be linked to reduced mortality risks, and people who consume more may enjoy even lower risks, according to a report examining coffee consumption among more than 400,000 people in the May 17 issue of the New England Journal of Medicine.
Compared with men who didn’t drink coffee, those who drank six or more cups per day had a 10% lower risk of death during a median follow-up of 14 years. Compared with women who didn’t drink coffee, those who drank six or more cups per day had a 15% lower risk, reported Neal D. Freedman, Ph.D., of the National Cancer Institute’s Division of Cancer Epidemiology and Genetics, and his associates.
The benefit of coffee consumption was similar between people who predominantly drank decaffeinated and those who predominantly drank caffeinated coffee, so caffeine does not appear to be the component of the beverage that improves mortality, they said.
In previous studies, coffee drinking has been linked to lower rates of diabetes, inflammatory diseases, and stroke. But studies examining a link with heart disease have produced mixed results, and "associations with cancer have generally been null," the researchers noted. Thus, coffee’s association with total mortality has been mixed.
Dr. Freedman and his colleagues used data from the National Institutes of Health–AARP Diet and Health Study to assess the relationship between coffee drinking and both total and cause-specific mortality. The NIH-AARP study involved more than 617,000 subjects aged 50-71 years who were followed from baseline (1995-1996) through 2008, so it had ample power to detect even modest associations, the investigators noted.
For the Diet and Health Study, subjects residing in six states and two cities answered a comprehensive questionnaire about diet and lifestyle at baseline. Dr. Freedman and his associates assessed a subgroup of 229,119 men and 173,141 women from this study population, after excluding those with cancer, heart disease, stroke, or inadequate information on coffee drinking and cigarette smoking.
A total of 33,731 men and 18,784 women died during follow-up. The researchers found a modest inverse association between coffee drinking and total mortality for both sexes (N. Engl. J. Med. 2012;366:1891-1904).
This association was dose dependent. Hazard ratios for death from any cause among men who drank coffee, compared with men who did not, were 0.99 for less than one cup per day, 0.94 for one cup, 0.90 for two to three cups, 0.88 for four to five cups, and 0.90 for six or more cups.
Hazard ratios among women who drank coffee, compared with women who did not, were 1.01 for less than one cup per day, 0.95 for one cup, 0.87 for two to three cups, 0.84 for four to five cups, and 0.85 for six or more cups.
These hazard ratios are similar to those found in several larger, more recent studies, including the Nurses’ Health Study and the Health Professionals Follow-up Study, the investigators said.
In an analysis of the data stratified by the predominant type of coffee consumed, the link between intake and mortality was similar for caffeinated and decaffeinated coffee. This suggests that the mortality benefit is due to some compound contained in coffee other than caffeine, such as antioxidants.
The association also persisted across numerous subgroups of study participants, regardless of age; body mass index; the presence or absence of diabetes; concomitant alcohol consumption; high or low intake of red meat, white meat, fruit, and vegetables; and use or nonuse of hormone replacement therapy.
The strongest inverse associations between coffee drinking and total mortality were found among people who had never smoked (compared with current smokers) and those who reported having very good to excellent overall health (compared with poor to fair health).
When cause-specific mortality was examined, coffee intake was inversely related to most major causes of death in both men and women. Higher coffee consumption was linked to lower mortality due to heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.
However, coffee did not protect against cancer mortality in women, and it showed a borderline positive association with cancer mortality in men.
"Given the observational nature of our study, it is not possible to conclude that the inverse relationship between coffee consumption and mortality reflects cause and effect," the investigators said.
Nevertheless, "our results provide reassurance with respect to the concern that coffee drinking might adversely affect health."