The findings, published in the Stroke journal, were not observed in those consuming sugar-sweetened beverages as researchers warned of the implications arising from the increase in soft drinks sweetened with sugar alternatives.
“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,” said lead study author Dr Matthew Pase, senior fellow at Boston University School of Medicine.
“Even if someone is three times as likely to develop stroke or dementia, it is by no means a certain fate,” he added.
“In our study, three percent of the people had a new stroke and five percent developed dementia, so we're still talking about a small number of people developing either stroke or dementia.”
The paper added its long-term observational study design was not able to prove cause and effect.
In addition, the results were also only able to show this trend among one group of people.
‘Artificially-sweetened drinks have a role’
Using data obtained from the Framingham Heart Study, the team from Boston University reviewed the drinking habits of 2,888 people.
The subjects were primarily Caucasian, over the age of 45 for the stroke study and 1,484 people over the age of 60 for the dementia arm of the study.
Participants reported their eating and drinking habits via food frequency questionnaires.
Over a decade, the team then looked into those who developed stroke or dementia making associations with the dietary information given.
The data collected did not distinguish between the types of artificial sweeteners used in the beverages.
At the end of the 10-year follow-up period, the researchers noted 97 cases (3%) of stroke, 82 of which were caused by blockage of blood vessels. The team also noted 81 (5%) cases of dementia, 63 of which were diagnosed as Alzheimer’s disease.
“We know that limiting added sugars is an important strategy to support good nutrition and healthy body weights, and until we know more, people should use artificially sweetened drinks cautiously,” said Dr Rachel Johnson, professor of nutrition at the University of Vermont.
“They may have a role for people with diabetes and in weight loss, but we encourage people to drink water, low-fat milk or other beverages without added sweeteners.”
Artificially sweetened beverages are typically sweetened with non-nutritive sweeteners, such as aspartame and sucralose.
In 2013, The European Food and Safety Authority (EFSA) declared aspartame to be safe for the general population at current consumption levels (40 mg per kg of bodyweight per day).
A typical diet soft drink contains about 180 mg of aspartame in a can.
Industry group response
The International Sweeteners Association (ISA) responded to the findings pointing out these was no plausible mechanism offered to explain the causal relationship between diet drinks’ consumption and stroke and dementia.
“When prevalent hypertension, the single most important stroke risk factor, was taken into account in the statistical analysis, the association between diet drinks and incident all-stroke was already attenuated,” a spokesperson said.
“Similarly, the magnitude of the association of diet drinks with dementia decreased further when the authors considered the influence of diabetes as a potential confounding factor.
“Lastly, another limitation of this study is the method used for dietary intake data (self-reported food frequency questionnaire (FFQ)), which may be subject to recall bias, thus introducing error into the estimated models.”
Gavin Partington, BSDA Director General also added his voice to the findings.
He said that despite the claims the authors admitted they found no cause and effect and provided 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.”
Tam Fry, a spokesman for the National Obesity Forum, urged consumers not to view low- or no-sugar drinks as a healthy alternative.
"Don't be fooled by the use of the word diet. Diet drinks were dreamed up as a description by an industry wanting to lull you into believing that it was a healthy thirst quencher. Whether you're thin or fat and thirsty, and not near a good old fashioned tap, buy yourself bottled water.
“It also has to be said that diet drinks are also as dangerous for tooth decay as the full sugar version: it is the phosphorous and citric acids in both beverages that can be ruinous to teeth - especially children's."