Coffee Consumption Linked to Lower Risk for Death

Steven Fox

May 16, 2012

May 16, 2012 — The controversy about whether coffee is harmful or healthful just got a jolt of java.

Results from the largest study carried out to date indicate that coffee consumption was inversely associated with total and cause-specific mortality.

Men who drank 2 to 3 cups of coffee daily had a 10% decrease in their risk for death during the 13 years of the study compared with men who drank no coffee. Women who drank 2 to 3 cups of coffee daily had a 13% decrease in their risk for death.

The study, conducted by Neal Freedman, PhD, from the Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, Maryland, and colleagues, appears in the May issue of the New England Journal of Medicine.

"Considerable attention has been focused on the possibility that coffee may increase the risk of heart disease, particularly since drinking coffee has been associated with increased low-density lipoprotein cholesterol levels and short-term increases in blood pressure," the authors note.

However, the results of prior studies looking into that association have been inconsistent. The authors say that may be because of differences in the way the studies were conducted (case-controlled vs prospective study designs) or because previous researchers have not adequately controlled for potentially confounding variables such as tobacco smoking.

In addition to those potential limitations, the authors note, the total number of deaths examined in previous studies has been relatively small.

In an effort to address those issues, this group of researchers checked into the association of coffee consumption with subsequent total and cause-specific mortality in 229,119 men and 173,141 women who completed questionnaires as part of the wide-ranging National Institutes of Health–AARP Diet and Health Study.

When joining the study, participants were given questionnaires that, among other things, asked them about their coffee consumption. Ages at that baseline assessment ranged from 50 to 71 years. People with cancer or heart disease and those who had a history of stroke were excluded from the study.

During the 13-year study (1995 - 2008), 33,731 men and 18,784 women died. When the investigators used age-adjusted models to assess those results, they found that risks for death were elevated for coffee drinkers compared with those people who did not drink coffee.

However, those who drank coffee were also more likely to be smokers, and when the researchers adjusted for smoking status as well as other potentially confounding variables, a very different picture emerged.

"In this large, prospective U.S. cohort study, we observed a dose-dependent inverse association between coffee drinking and total mortality, after adjusting for potential confounders (smoking status in particular)," they write.

More specifically, they found that men who consumed 6 or more cups of coffee each day were 10% less likely to die during the study period than were men who did not drink coffee. For women, the reduction in risk was even greater, at 15%.

Hazard ratios for mortality in men who drank coffee compared with men who did not (P < .001 for trend across categories) were:

  • less than 1 cup of coffee per day: 0.99 (95% confidence interval [CI], 0.95 - 1.04),

  • 1 cup: 0.94 (95% CI, 0.90 - 0.99),

  • 2 to 3 cups: 0.90 (95% CI, 0.86 - 0.93),

  • 4 to 5 cups: 0.88 (95% CI, 0.84 - 0.93), and

  • 6 or more cups: 0.90 (95% CI, 0.85 - 0.96).

Corresponding hazard ratios for women (P < .001 for trend across categories) were:

  • less than 1 cup of coffee per day: 1.01 (95% CI, 0.96 - 1.07),

  • 1 cup: 0.95 (95% CI, 0.90 - 1.01),

  • 2 to 3 cups: 0.87 (95% CI, 0.83 - 0.92),

  • 4 to 5 cups: 0.84 (95% CI, 0.79 - 0.90), and

  • 6 or more cups: 0.85 (95% CI, 0.78 - 0.93).

As for cause-specific mortality, the researchers say they noted inverse associations for deaths resulting from heart disease, stroke, diabetes, respiratory disease, infections, injuries, and accidents, but the same was not true of deaths from cancer.

"In contrast, there was no significant association between coffee consumption and deaths from cancer in women," the researchers say. They also found a borderline positive association in men. Of the 13,402 deaths from cancer, 880 deaths were in men who consumed at least 6 cups of coffee each day (hazard ratio, 1.08; 95% CI, 0.98 - 1.19; P = 0.02 for trend).

Mortality rates were similar across all subgroups, the researchers note. That included people who had never smoked as well as those who at baseline described themselves as being in very good or excellent health.

The authors emphasize several limitations of the study. For one, coffee consumption was assessed at only a single point in time (upon entry into the study), so it is possible that consumption patterns might have changed over time.

In addition, the researchers note that they lacked specifics on how study participants prepared their coffee, and it could be that healthful and/or harmful attributes of the coffee might change depending on how it is prepared.

Still, they note, this study was larger than any previous study, and the number of deaths (>52,000) was more than double that in any earlier study.

"Our results provide reassurance with respect to the concern that coffee drinking might adversely affect health," they conclude.

The research was supported by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, Division of Cancer Epidemiology and Genetics. The authors have disclosed no relevant financial relationships.

N Engl J Med. 2012;366:1891-1904. Abstract

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