Stroke and Dementia Risks With Sugars and Artificial Sweeteners: Fact or Fiction?

Researchers use data from large ongoing cohort study to look for connection.

In a recent study, researchers concluded that sugar and artificially sweetened beverage intake have been linked to cardiometabolic risk factors, which increase the risk of cerebrovascular disease and dementia. The study examined whether sugar or artificially sweetened beverage consumption was associated with the prospective risks of incident stroke or dementia in the community-based Framingham Heart Study Offspring cohort.

2,888 participants 45 years of age and older for incident stroke (mean age 62 [SD, 9] years; 45% men) and 1,484 participants 60 years of age and older for incident dementia (mean age 69 [SD, 6] years; 46% men)., were studied. Beverage intake was quantified using a food-frequency questionnaire.

After adjustments for age, sex, education (for analysis of dementia), caloric intake, diet quality, physical activity, and smoking, higher recent and higher cumulative intake of artificially sweetened soft drinks were associated with an increased risk of ischemic stroke, all-cause dementia, and Alzheimer’s disease dementia. When comparing daily cumulative intake to 0 per week (reference), the hazard ratios were 2.96 (95% confidence interval, 1.26–6.97) for ischemic stroke and 2.89 (95% confidence interval, 1.18–7.07) for Alzheimer’s disease. Sugar-sweetened beverages were not associated with stroke or dementia.

From the results, it was concluded that artificially sweetened soft drink consumption was associated with a higher risk of stroke and dementia.

While preliminary research found a link between daily intake and increased risk, the chain of evidence is not as strong as reported. The researchers analyzed data from an ongoing U.S. cohort study to see if consumption of sugar or artificially sweetened drinks was linked with risk of stroke or dementia 10 years later. Several thousand people were included in the study, and during follow-up 3% had a stroke and 5% developed dementia. Overall, when taking account of all health and lifestyle factors that could have an influence, contrary to the results offered, the researchers actually found no link between artificially sweetened drinks and risk of dementia.

The figures reported in the media came from a model that wasn’t adjusted for all confounders, such as diabetes, that could explain part of the link. For stroke, the links with artificially sweetened drinks were inconsistent. There were no overall links when looking at longer-term patterns. The study does not give definitive “cause and effect” proof that drinking artificially sweetened drinks will lead to stroke or dementia. Still, the lead author’s reported statement that it is healthier (not to mention cheaper) to just drink water is sound advice.

This was all started by the study which was carried out by researchers from Boston University School of Medicine and Tufts University, Boston. The study was published in Stroke, a peer-reviewed journal of the American Heart Association, on an open-access basis. The Guardian gave a good overview of the research while making clear that no cause and effect had been proven. The Daily Mail’s headline – “Diet drinks TRIPLE your risk of stroke and dementia” – is somewhat misleading as it is based on unadjusted data.

This was a prospective cohort study, using data collected from the ongoing Framingham Heart Study Offspring, to see whether drinking sugar or artificially sweetened drinks was linked with risk of stroke or dementia. The researchers say how previous research has linked both types of soft drink with cardiovascular disease, like stroke, but dementia had yet to be examined. This type of large cohort can find links, but it’s very difficult to prove that any individual factor, such as drinks, is directly responsible for a health outcome. Food questionnaires can be subject to inaccurate recall and it’s hard to account for all other health and lifestyle factors.

During follow-up there were 97 cases of stroke (3% of the cohort), 82 of which were caused by a clot (ischemic). There were 81 new diagnoses of dementia (5%), 63 of which were consistent with Alzheimer’s.

When adjusted for all confounders, there was no link between any consumption of either total sugary drinks or sugar-sweetened drinks and risk of stroke. They did find significant links for artificially sweetened drinks when looking at recent history. Recent consumption of artificially sweetened drinks (at the 1998–2001 assessment) was linked with risk of stroke:

For overall intake across all assessment periods, however, there was no significant link between artificially sweetened drinks and strokes – this was only found again when restricting to the smaller number with ischemic stroke.

The reported figure of a tripled increase with artificially sweetened drinks comes from an HR of 2.67 (95% 1.26 to 6.97) for one or more drinks per day (but this was in the model that was not fully adjusted for all health factors) and for ischemic stroke only.

In the fully adjusted model, there were no significant links for risk of dementia (or Alzheimer’s specifically) from total sugary drinks, sugar-sweetened drinks or artificially sweetened drinks.

In conclusion, care must be taken when interpreting the results. Several points need to be considered:

1. The new number of strokes and dementia in this study was small, just 3% and 5% of the cohort, respectively.
2. The paper doesn’t report how many of the 97 people with stroke or 81 with dementia were in the highest consumption categories. The numbers will get even smaller when restricting to the 82 with ischemic stroke and 63 with Alzheimer’s. Analysis with smaller numbers can be less accurate, as indicated by the rather wide confidence intervals on the tripled associations.
3. The researchers grouped consumption categories according to the most common response. The categories for the three different drinks aren’t consistent, which makes it quite difficult to compare them with one another. Overall this makes it very difficult to conclude with any certainty that artificially sweetened drinks carry more risk than sugary drinks.
4. Food frequency questionnaires are a validated measure for assessing food and drink consumption. However, people may not be able to accurately recall how much and how often they have consumed a particular drink over the past year.
5. Lastly, this is a sample from one region of the U.S. only. Lifestyle habits, including drink consumption, may differ and the findings may not have been the same if studying other samples.

Practice Pearls:

• Overall, the various limitations mean that this study does not give definitive proof that drinking artificially sweetened drinks will increase risk of stroke or dementia.
• When it comes to the healthiest drink to have on a day-to-day basis, the study recommends plain old water.

References:  

Consumption of added sugars among US children and adults by food purchase location and food source. Am J Clin Nutr. 2014;100:901–907. doi: 10.3945/ajcn.114.089458.

Prospective associations and population impact of sweet beverage intake and type 2 diabetes, and effects of substitutions with alternative beverages. Diabetologia. 2015;58:1474–1483. doi: 10.1007/s00125-015-3572-1.

Sugar-sweetened and artificially sweetened beverage consumption and risk of type 2 diabetes in men. Am J Clin Nutr. 2011;93:1321–1327.doi: 10.3945/ajcn.110.007922.

Consumption of added sugars is decreasing in the United States. Am J Clin Nutr. 2011;94:726–734. doi: 10.3945/ajcn.111.018366.

World Health Organization. WHO Calls on Countries to Reduce Sugars Intake Among Adults and Children. http://www.who.int/mediacentre/news/releases/2015/sugar-guideline/en/.

Sugar-sweetened beverages and risk of metabolic syndrome and type 2 diabetes: a meta-analysis. Diabetes Care. 2010;33:2477–2483. doi: 10.2337/dc10-1079.