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A new report, published by the Institute for Scientific Information on Coffee, investigates the association between coffee, caffeine, mortality and life expectancy.
Dr Robin Poole, Specialty Registrar in Public Health, Primary Care and Population Sciences Academic Unit, University of Southampton, said:
“This report is a summary of discussions about existing research, most of it previously published, looking at associations between drinking coffee and lower risk of dying from any cause. Unpublished data was discussed by some of the experts – the finer details of this unpublished work aren’t unavailable to critique, but these associations (but not causations) are reasonably well established. The associations between drinking coffee and reduced risk of early death found in previously-published research are fairly solid. However, these associations are from observational types of research, and there are confounding factors that could explain the associations. In other words, we still cannot say with certainty that for an individual drinking more coffee can lead to a longer life span – it could be something else such as income or other aspects of the diet which are responsible.
“The report discusses smoking as a confounding factor in some detail. Not taking smoking into account in statistical analyses in studies is likely to reduce the size of beneficial associations, so the argument is that when properly taking smoking into account the benefits of coffee appear even more pronounced. But there is little discussion around possible confounding factors going the other way, such as those that may be both associated with drinking more coffee and with being healthier, such as income, which may falsely lead to an apparent beneficial associations between coffee and lower risk of dying.
“The report is a springboard to highlight the current level of scientific understanding around the link between drinking coffee and lower risk of dying from any cause. The report was from a round table discussion of experts from a number of academic and clinical backgrounds and highlighted coffee being a credible component of a healthy diet.
“There is not much discussion about the variability in what is in a cup of coffee, and misclassification of coffee intake is very likely here because there is no standard cup size and coffee varies depending on the type of bean, roast, grind and preparation method. However, this is more likely to dilute risk estimates than to strengthen them and so beneficial associations would probably not be affected by this.
“The report hints at being able to recommend coffee to patients at risk of type 2 diabetes and cardiovascular disease – however, I think we are still not at the stage where we can recommend people start to drink coffee, or increase intake, as a means of preventing specific diseases or living longer. I think existing evidence such as this serves to reassure those who are currently drinking moderate amounts of coffee that it can be enjoyed as part of a healthy diet. But some individuals are sensitive to the effects of caffeine, which for some can lead to headache, frequent urination and insomnia, and so these people are unlikely to tolerate increasing their intake. The report also importantly highlights the importance of drinking healthier coffee (i.e. not with lots of sugar and cream). Finally the report highlights the need for further research into the associations especially into the mechanisms that might explain the potential benefit, and this also is entirely reasonable.”
* ‘Roundtable report: Coffee, caffeine, mortality and life expectancy’ will be published by the Institute for Scientific Information on Coffee on Wednesday 1 August 2018.
Declared interests
Dr Robin Poole: “No conflicts of interest apart from I am the author of one of the papers cited in the report (Poole et al 2017) and I do drink coffee!”