Sugar intake heightens stroke, dementia risk

Neurologists at Boston University recently discovered a direct relationship between drinking sugary drinks like soda and an increased risk for stroke and dementia.

Each year 795,000 people experience a stroke, making it the leading cause of long-term disability and the fifth leading cause of death in the United States. A stroke occurs when blood flow to the brain is cut off and brain cells begin to die because they are deprived of oxygen.

The National Stroke Association lists several factors that can cause a stroke and recommends eating a healthy diet consisting of a variety of vegetables, fruits and grains. They also recommend limiting saturated fats, trans fats and added sugars. In fact, they recommend consuming fewer than 10 percent of calories per day from added sugars.

Currently, 47.5 million people suffer from dementia across the globe. Each year there are 7.7 million new cases. Dementia describes a group of symptoms that affect memory, thinking and social abilities severely enough to interfere with daily functioning.

Alzheimer’s disease is the most common cause of progressive dementia in older adults, affecting 60 to 70 percent of the population worldwide. A diet of reduced sugars and fat, with lots of fruits, vegetables and whole grains has been shown to reduce the risk of Alzheimer’s.

In the past, research has shown that the development of stroke and dementia are both linked to the onset of atherosclerosis and type 2 diabetes mellitus, both of which are caused by diets high in sugars.

The neurologists at Boston University questioned if eating more sugar or drinking more sugary sodas increased a patient’s risk for stroke or dementia. Matthew Pase, a fellow in the Department of Neurology at the Boston University School of Medicine (BUSM), and his team tested their hypothesis on patients from the Offspring Cohort of the Framingham Heart Study (FHS)  which is under the umbrella of the National Heart, Lung, and Blood Institute.

Started in 1948, the founders of the FHS aimed to identify risk factors for heart disease by following a group of patients over a long period of time who had not yet developed symptoms of cardiovascular disease, or suffered a heart attack or a stroke. To do so, the researchers at the FHS recruited 5,209 men and women between the ages of 30 and 62 from the town of Framingham, Mass.

This group of men and women is referred to as the Original Cohort. Once enrolled in the study, the scientists began conducting extensive physical exams and lifestyle interviews on the patients, looking for common patterns related to heart disease development. Participants have since returned every two years to update their health information.

In the 1970s, the research team enrolled 5,124 of the original participant’s adult children and their spouses to participate in the study as well. This second group is known as the Offspring Cohort.

Focusing on 2,888 participants from the Offspring Cohort who were all over 45 years old, the research team looked at their risk for stroke. Over the course of three examinations, between the years of 1991-1995, 1995-1998 and 1998-2001, participants were asked to fill out a food-frequency questionnaire, a checklist of foods and drinks which had a section that asked how often someone ate or drank something over a given period of time. Pase described why they used sugary drinks in their study in an article by  Science Daily.

“It’s difficult to measure overall sugar intake in the diet, so we used sugary beverages as a proxy,” Pase said.

Using information from each visit, the research team evaluated how often a patient ate sugar or drank a sugary drink by averaging the patient’s answers. Over the course of 10 years the team observed 97 strokes. Their data revealed that compared to people who eat or drink no additional sugar during the day, people who do are 2.96 times more likely to have a stroke.

The researchers used 1,484 patients above the age of 60 to conduct a similar test on dementia. They  team observed 81 cases of dementia and discovered that patients who drink eat or drink more sugar are 2.89 times as likely to develop Alzheimer’s. Pase and his group also performed a second follow-up study that focused exclusively on Alzheimer’s.

In this study, the team looked at how sugary drinks caused Alzherimer’s by using an MRI scanner and cognitive testing in about 4,000 people enrolled in the FHS Offspring and Third-Generation cohorts, who the grandchildren of the Original Cohort.

Focusing on people in the “high intake” group who drank more than two sugary drinks a day, they found multiple signs of accelerated brain aging, including smaller overall brain volume, poorer episodic memory and a shrunken hippocampus, all risk factors for early-stage Alzheimer’s disease.

BUSM neurology professor Sudha Seshadri summarized their findings in an article by Science Daily.

“These studies are not the be-all and end-all, but it’s strong data and a very strong suggestion,” Seshadri said. “It looks like there is not very much of an upside to having sugary drinks, and substituting the sugar with artificial sweeteners doesn’t seem to help.”