Anna Hartz
Coffee is one of those everyday drinks that often gets caught between health warnings and health advice.
One week it is said to be good for us. The next week, a new study appears to suggest the opposite. Recent headlines have once again made coffee sound like a possible weapon against dementia.
18 percent lower risk
A recent study from researchers at Harvard University looked at health data from more than 131,000 Americans between 1980 and 2023. The researchers found that people who drank between one and five cups of coffee a day had an 18 percent lower risk of developing dementia than people with very low caffeine intake, reports Videnskab.
The strongest link was found among people who drank two to three cups of coffee a day. A similar pattern was seen among people who drank one to two cups of caffeinated tea each day.
The findings led to headlines suggesting that coffee could help prevent dementia. But several researchers say the study cannot prove that.
Professor Karsten Juhl Jørgensen from the University of Southern Denmark agrees with the criticism. He says the study does not tell us whether drinking coffee actually changes a person’s risk of dementia.
One problem is smoking. The study adjusted for smoking and other factors such as diet, education, income and alcohol use. But researcher Jennifer Dowd says there may still be an important problem.
People who smoke heavily are more likely to die earlier. Some heavy coffee drinkers in the study may therefore have died before they had a chance to develop dementia. This could make dementia appear less common among coffee drinkers.
In the big picture?
There is also the problem of memory. Participants were asked to remember how much coffee they drank. People do not always remember their habits accurately. This can be especially difficult when researchers study changes in memory and thinking over many years.
Alcohol use may also have affected the results. The study considered alcohol consumption but did not fully separate different drinking patterns. People with low coffee intake may have had other habits that increased their dementia risk.
The researchers themselves say their study only found a connection between coffee drinking and dementia risk. It does not prove that coffee or caffeine prevents dementia.
The Danish media site Videnskab presented the study for the National Dementia Knowledge Centre in Denmark. They responded that they do not claim that coffee prevents dementia. The centre points out that the evidence comes from observational research, which can show links but cannot prove cause and effect.
