Longevity link: Coffee drinking and reduced mortality risk

Scientists have given long-term coffee drinkers a reason to smile, reporting that increased coffee consumption is associated to reduced risk of death. “Coffee is a widely consumed beverage worldwide, but the relationship of coffee drinking with health has been unclear,” says Dr Neal Freedman from the Division of Cancer Epidemiology and Genetics at the National Cancer Institute (NCI) in America. “Our intended aim was to investigate whether coffee drinking was associated with total risk of death over the course of our study and to look at various different causes of death.” Freedman and his colleagues conducted an observational study on more than 400,000 people over 14 years. The study consisted of about 229,000 men and 173,000 women between 50 to 71 years old. Participants completed a questionnaire between 1995 to 1996 as part of the National Institute of Health (NIH) AARP Diet and Health study. Participants answered questions about their coffee intake, demographics, diet and behaviours, and were tracked until 31 December 2008, or until the date they died, whichever came first. People who had previously had cancer, heart disease or some other serious illness were excluded from the study. Freedman says the study is the largest-ever analysis of coffee and mortality risk.
The results, published in May 2012 in the New England Journal of Medicine, found that increased coffee consumption reduced the risk of death.  Compared to the men and women who did not drink coffee, participants who consumed three or more cups of coffee a day had approximately 10 per cent lower risk of death. Women who drank six cups of coffee per day had a 15 per cent reduced risk of death compared with non-drinkers, while men consuming the same amount had a 10 per cent reduced risk. In addition, the researchers found that coffee was also associated with lowered risk of death from specific diseases, such as heart disease, respiratory disease and diabetes, stroke and infections. The researchers accounted for differences between coffee drinkers and non-drinkers such as body mass, smoking status, the consumption of alcohol and the intake of red meat, white meat, vitamins, fruits and vegetables. Coffee drinking was not associated with cancer mortality among women, but researchers did find a statistically significant association of heavier coffee intake with increased risk of cancer death among men. Freedman says no correlation was found between participants who drank regular coffee or decaffeinated coffee, therefore suggesting that the benefit comes from one of coffee’s other 1000 compounds. Reduced risk of death was also strongly linked in coffee drinkers who had never smoked. Freeman found that among those who smoked, coffee consumption could have some benefit. Because the study was observational in nature, Freedman says it has some limitations. Coffee intake was assessed by self-report only once at the beginning of the study, and there was no information about how the coffee was prepared, such as filtered, instant or espresso.  “Coffee drinking is associated with many risk factors of death, like smoking, and so we had to conduct our analysis very carefully in order to take these associations into account,” Freedman says. “Coffee has been suggested as both harmful and helpful towards health and so we were not sure
what to expect in our study.” Despite these promising results for coffee drinkers, Freedman cautions that coffee intake alone won’t help people live longer.
“As an observational study, we don’t know that coffee itself is having the effect. It might be something else associated with coffee drinking and the risk of death,” he says. “Coffee has many different components, and so if there truly is a mechanism between coffee and disease, the mechanism responsible still needs to be determined.” With many relations between coffee and health still unanswered for, Freedman says he will pursue further research including the effect of coffee preparation and the roles of individual coffee compounds in health. For now, however, he says coffee drinkers can sip away with peace of mind. “We believe that our results provide some reassurance for people who enjoy drinking coffee but had worried that it may have negative health effects,” he says. “However, coffee should not be considered to be a health remedy.” GCR