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Coffee and mortality: what the latest study says

 

Go ahead and have that cup of coffee because new research shows it may boost chances for a longer life, even for those who down at least eight cups daily.

In a study of nearly half-a-million British adults, coffee drinkers had a slightly lower risk of death over 10 years than abstainers.

The apparent longevity boost was seen with instant, ground and decaffeinated, results that echo US research.

Overall, coffee drinkers were about 10 per cent to 15 per cent less likely to die than abstainers during a decade of follow-up.

The results don’t prove your coffee pot is a fountain of youth nor are they a reason for abstainers to start drinking coffee, said Alice Lichtenstein, a Tufts University nutrition expert who was not involved in the research.

But she said the results reinforce previous research and add additional reassurance for coffee drinkers.

“It’s hard to believe that something we enjoy so much could be good for us. Or at least not be bad,” Lichtenstein said.

The study was published on Monday in the journal JAMA Internal Medicine.

It’s not clear exactly how drinking coffee might affect longevity.

Lead author Erikka Loftfield, a researcher at the US National Cancer Institute, said coffee contains more than 1000 chemical compounds including antioxidants, which help protect cells from damage.

Other studies have suggested that substances in coffee may reduce inflammation and improve how the body uses insulin, which can reduce chances for developing diabetes.

For the study, researchers invited 9 million British adults to take part; 498,134 women and men aged 40 to 69 agreed. The low participation rate means those involved may have been healthier than the general UK population, the researchers said.

Participants filled out questionnaires about daily coffee consumption, exercise and other habits, and received physical exams including blood tests. Most were coffee drinkers; 154,000 or almost one-third drank two to three cups daily and 10,000 drank at least eight cups daily.

During the next decade, 14,225 participants died, mostly of cancer or heart disease.

Coffee drinkers in the UK study didn’t have higher risks than non-drinkers of dying from heart disease and other blood pressure-related causes.

As in previous studies, coffee drinkers were more likely than abstainers to drink alcohol and smoke, but the researchers took those factors into account, and coffee drinking seemed to cancel them out.

You can access the study here.

What does the research tell us about coffee’s health benefits?

A recent headline in the Australian newspaper claimed “A short black a day can keep heart attack at bay”:

American scientists have unearthed fresh evidence that coffee exerts protective effects against heart failure and stroke.

According to the researchers, for every extra cup of coffee drunk per week, there was a 7% reduction in risk of heart failure and an 8% risk reduction for stroke.

So, is this more good news for coffee lovers, or a case of be careful what you read?

As the researchers explain in the media article:

We don’t know if it’s the coffee, compounds in the coffee or behaviour associated with drinking coffee.

The data comes from observational studies showing an association between coffee consumption, and heart failure and stroke. It does not prove causation. It shows that people who drank more coffee had lower rates of heart failure and stroke, not that drinking more coffee was responsible for reducing this risk.

There may be other reasons why people with heart failure and those who have had a stroke drink less coffee, for example, being on fluid restrictions for medical reasons, or not being able to move independently enough to make a cup of coffee.

That doesn’t mean you should avoid having another cup of coffee. A review of 20 observational studies from 2014 found those who drank the most coffee had longer life expectancies than those who drank the least or no coffee.

Again, these studies showed correlation not causation, but the evidence to suggest coffee is good for you is mounting.

How was the research conducted?

This story came from an abstract of a presentation to the American Heart Association’s 2017 Scientific Sessions on November 14. The researchers used data from more than 12,000 adults in the Framingham Heart Study to look for eating and drinking habits associated with heart disease.

The study used a powerful new statistical approach called random forest machine-learning methods. This uses all the individuals’ data to construct multiple decision trees and work out what the common patterns are when predicting their health outcomes. The researchers said this technique was a bit like the algorithms used in the marketing programs that predict our shopping behaviours.

The researchers confirmed that high blood pressure, high blood cholesterol and older age increased the risk of heart disease. They also identified that higher intakes of coffee predicted a lower risk of heart failure and stroke.

Important questions about the research are unclear: how coffee intake was assessed, whether decaffeinated coffee was included, and exactly how much was consumed each day or over the week.
Tim Wright/Unsplash

Lastly, the researchers created a statistical model that included the well-documented heart disease risk factors – age, sex, total and HDL (good) blood cholesterol levels, blood pressure, smoking and diabetes – that are used to calculate a person’s Framingham Risk Score. This is a person’s ten-year probability of developing cardiovascular disease, including stroke, heart failure and atherosclerosis (fatty deposits that clog arteries).

This analysis found that including coffee consumption in the equation improved the accuracy of the Framingham Risk Score in predicting heart failure and stroke by 4%.

The researchers reported finding similar trends – the 7% reduction in risk of heart failure and 8% risk reduction for stroke – in two separate studies.

What does this mean?

The study in the media headline was not about heart attack, it looked at heart failure and stroke, which are very different conditions:

  • Heart attack is triggered by short-term lack of blood and oxygen to the heart muscle causing some muscle cells to die
  • Heart failure means the heart can’t pump blood around the body adequately
  • Stroke is when the blood supply to the brain is interrupted by either a blockage or a burst blood vessel.

This difference is important because while something might be good for the heart muscle itself, it’s not necessarily good for the blood vessels in the heart and brain.

The data was from a conference abstract only. So it includes very limited details of the methods and results, and misses important information such as:

  • which variables were adjusted for in the statistical analyses (external factors that might skew the results)
  • how coffee intake was assessed
  • whether decaffeinated coffee was included, and
  • exactly how much was consumed each day or over the week.

While it’s great to hear about early research findings, the data has not gone through the full peer review publication process and so we will have to wait to eventually read the full paper.

Most importantly, this data comes from observational studies and shows an association between coffee consumption and heart health. It does not prove causation.

So is coffee good for your health?

If you are a smoker, it’s wise to avoid regular coffee. A review of the best evidence found a higher risk of lung cancer for smokers who drank regular coffee, although drinking decaffeinated coffee was suggestive of a lower risk.

Among those with high blood pressure, caffeine in coffee does lead to an immediate increase in blood pressure that can last a few hours. However, there is no evidence of an overall higher risk of heart disease.

For a host of other reasons including a lower risk of type 2 diabetes, prostate cancer, liver cancer, and a longer life expectancy, drinking coffee is now on the list of things to consider to improve your overall health. – Clare Collins


Blind peer review

The ConversationThis is a fair and accurate assessment, and accords with the data from two studies published this year on death from any cause (and heart disease and stroke). –Ian Musgrave

Clare Collins, Professor in Nutrition and Dietetics, University of Newcastle

This article was originally published on The Conversation. Read the original article.