People who drink diet fizzy drinks daily are almost three times more likely to suffer a stroke or dementia, a new study has suggested.
Those who had at least one diet drink a day increased their risk compared to people who consumed less than one diet drink a week.
Researchers said there was no link between sugary drinks and an increased risk of stroke and dementia, but added that people should not view sugary drinks as a “healthier option”.
“We recommend that people drink water on a regular basis instead of sugary or artificially sweetened beverages,” they added.
The new research, published in the American Heart Association’s journal Stroke, is based on data from 4,300 people taking part in the Framingham Heart Study.
Those in the stroke arm of the study were aged 45 and over, while those in the dementia arm were over 60.
All participants filled in questionnaires on their food and drink intake at three separate points during the 1990s. Researchers then followed the group for 10 years.
The study showed that people who had at least one diet drink a day had an almost three times increased risk of dementia or stroke.
Researchers said future studies should look at the effect of diet drinks on factors known to increase the risk of stroke and dementia, such as high blood pressure.
“As the consumption of artificially sweetened soft drinks is increasing in the community, along with the prevalence of stroke and dementia, future research is needed,” they added.
Matthew Pase, senior fellow in the department of neurology at Boston University School of Medicine, said the study shows “a need to put more research into this area, given how often people drink artificially sweetened beverages”.
He added: “Although we did not find an association between stroke or dementia and the consumption of sugary drinks, this certainly does not mean they are a healthy option. We recommend that people drink water on a regular basis instead of sugary or artificially sweetened beverages.”
He continued: “Even if someone is three times as likely to develop stroke or dementia, it is by no means a certain fate.
“In our study, 3% of the people had a new stroke and 5% developed dementia, so we’re still talking about a small number of people developing either stroke or dementia.”
Researchers said further studies are needed to look into the link between drinks, dementia and stroke.
Gavin Partington, director-general of the industry-funded British Soft Drinks Association, told the Press Association: “Despite their claims, the authors of this observational study admit they found no cause and effect and provide no science-based evidence whatsoever to support their theories.
“In fact, based on the evidence, Public Health England is actively encouraging food and drink companies to use low-calorie sweeteners as an alternative to sugar and help people manage their weight.
“Surely we should be trying to help consumers reduce their calorie intake, not presenting unproven claims?”
Dr Rosa Sancho, head of research at Alzheimer’s Research UK, said: “This interesting new study has pointed to higher rates of dementia in people who drink more artificially-sweetened drinks, but it doesn’t show that these drinks are the cause of this altered risk.”