According to two new studies released April 20, drinking diet or artificially sweetened sodas may increase the consumer's risk of dementia, Alzheimer's disease and stroke. While the authors of both studies warn the results may represent correlation rather than causation, the reports do agree on one important fact: people who drink diet sodas tend to be in poorer health than those who don't.
The first study, conducted out of the Boston University School of Medicine and published in Stroke, analyzed more than 5,000 people. Initial testing began in 1948, the population sample expanding over time to include children and grandchildren of original subjects.
Lead researcher Matthew Pase told NBC News that the study "found that those people who were consuming diet soda on a daily basis were three times as likely to develop both stroke and dementia within the next 10 years as compared to those who did not consume diet soda ... "
The study did not track which specific artificial sweeteners or sugars were consumed by test subjects, only their overall consumption of such products. The research team reported "evidence to link consumption of artificially sweetened beverages with the risk of stroke," as well as "an association between daily intake of artificially sweetened soft drink and an increased risk of both all-cause dementia and dementia because of Alzheimer's disease."
The findings suggest further health risks with sugar-sweetened drinks, such as increased risk of diabetes and overall smaller brain volumes.
The second study, published in Alzheimer's & Dementia, found that higher consumption of sugary beverages by middle-aged consumers could be linked to symptoms of pre-clinical Alzheimer's, including smaller total brain volume and poor memory. According to Bloomberg, the results of the study are in line with those of the Boston Puerto Rican Health Study, which also found that higher sugar intake was associated with increased risk of developing Alzheimer's.
The authors of both studies addressed the difficulties of drawing conclusions from their studies, specifically the limitations of establishing causality in either. The study in Alzheimer's & Dementia used a homogeneous population, and all the data from the questionnaire are inherently unreliable.
The Stroke study's authors pointed out that, in addition to suffering limitations similar to those of the other study, whatever associations could be drawn could actually be a case of reverse causality, "whereby sicker individuals consume diet beverages as a means of negating a further deterioration of health."