Observational Findings Linking Intake of Sugar Containing Beverage Do Not Accurately Represent Americans’ Risk For Preclinical Alzheimer’s Disease

While a recent study alleges estimated intake of sugar containing beverages is associated with markers of preclinical Alzheimer’s disease, the observational nature of the study and other important limitations temper any significance of the findings.

In the study, “Sugary beverage intake and preclinical Alzheimer’s disease in the community”, Pase et al., analyzed data from a subset of participants in two cohorts of the Framingham Heart Study. The study included data collected during a single timepoint for two cohorts. The Offspring Cohort data was collected in 1998-2001 while data for the Third Generation cohort was collected in 2009-2011. Researchers collected data on the number of sugar-sweetened beverages (including soft drinks, fruit juice, and fruit drinks) which was reported by participants, neuropsychological assessment, and brain imaging through magnetic resonance imaging (MRI). This data was evaluated to determine if significant relationships could be identified in three statistical models that varied in the confounding factors that were considered. All models adjusted for age, sex, total caloric intake, and the time between food frequency questionnaire (FFQ) data collection and imaging/ neuropsychological outcomes. Additional adjustment for education was included for neuropsychological outcome data or age for MRI data. A second statistical model further adjusted for systolic blood pressure, hypertension treatment, current smoking status, cardiovascular disease, atrial fibrillation, left ventricular hypertrophy, total cholesterol, high-density lipoprotein cholesterol, prevalent diabetes mellitus, depressive symptoms and waist-to-hip ratio. The third statistical model included the adjustments in model one plus intake of saturated fat, trans-fat, and dietary fiber and self-reported physical activity. Additional adjustments were made to the data presented as the researchers report findings in relative terms of years of brain aging. The researchers stated, “For this purpose, we regressed each outcome score on age and compared differences in means attributable to the different categories of sugary beverage intake.”

“The most important risk factors—age, family history and heredity—can’t be changed, but emerging evidence suggests there may be other factors we can influence. Some of the actions individuals can take to reduce the risk for Alzheimer’s include reducing the risk for traumatic brain injuries, heart disease, diabetes, stroke, high blood pressure and high cholesterol.” – Alzheimer’s Association

The researchers report that greater reported intake of sugar-containing beverages or low-calorie sweetened beverages was associated with lower total brain volume. Sugar-containing beverage intake was associated with poorer episodic memory and greater imaging indicative of cerebral small vessel disease that was not found in the statistical model that included saturated fat, trans-fat, dietary fiber and self-reported physical activity as confounding factors. The authors stated that, “Our findings indicate an association between higher sugary beverage intake and markers of preclinical Alzheimer’s disease, including lower brain volume and poorer memory.”

Points of Consideration

  • The study identified an association at a single time point and did not explore if this association is still present over time. The study cannot be used to consider whether the reported associations between sugary beverage intake and brain volume or cognition are causal or temporal.
  • The research did not include adjustment for multiple statistical testing and some of the findings may be due to chance.
  • The study does not represent a diverse populations with limits the generalizability of the findings.
  • Importantly, including two cohorts of the Framingham Heart Study may confound the study conclusions as the most important risk factors for Alzheimer’s include age, family history, and heredity.

According to the Alzheimer’s Association “The most important risk factors—age, family history and heredity—can’t be changed, but emerging evidence suggests there may be other factors we can influence. Some of the actions individuals can take to reduce the risk for Alzheimer’s include reducing the risk for traumatic brain injuries, heart disease, diabetes, stroke, high blood pressure and high cholesterol.”

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