Too Much Salt, Too Little Exercise Is Recipe for Dementia

Eating too many salty foods and getting little exercise is a recipe for more than heart disease in older adults. According to a Canadian study, it can also raise your risk for dementia.

The study, which appears online in the journal Neurobiology of Aging, followed the sodium consumption and physical activity levels of 1,262 healthy older Canadian men and women (ages 67 – 84), over three years. The adults were recruited from a large pool of participants in the Quebec Longitudinal Study on Nutrition and Successful Aging (NuAge).

While low sodium intake is associated with reduced blood pressure and risk of heart disease, this is believed to be the first study to extend the benefits of a low-sodium diet to brain health in healthy older adults.

"We have generated important evidence that sodium intake not only impacts heart health, but brain health as well," said Dr. Alexandra Fiocco, a scientist with Toronto's Baycrest's Kunin-Lunenfeld Applied and Evaluative Research Unit (KLAERU) and the study's lead investigator.

Health Canada recommends that people 14 years of age and older consume no more than 2,300 mg of sodium per day in their diet. (In the United States, the 2010 Dietary Guidelines for Americans recommend no more than 2,300 mg daily for adults, but no more than 1,500 mg daily for people more than 51 years old or if you have high blood pressure, diabetes, or kidney disease.)

In the Baycrest study, senior participants were assessed as low-, mid-, or high-level sodium consumers based on a food frequency questionnaire they each completed. Low-sodium intake was defined as not exceeding 2,263 mg/day; mid-sodium intake 3,090 mg/day; and high-sodium intake 3,091 and greater (this went as high as 8,098) mg/day.

Researchers used a modified Mini-Mental State Examination to measure cognitive function in participants at year one (baseline) and annually for three additional years. Physical activity levels were measured using the Physical Activity Scale for the Elderly.

"The results of our study showed that a diet high in sodium, combined with little exercise, was especially detrimental to the cognitive performance of older adults," said Dr. Fiocco.

"But the good news is that sedentary older adults showed no cognitive decline over the three years that we followed them if they had low sodium intake."

"These data are especially relevant as we know that munching on high-salt processed snacks when engaged in sedentary activities, such as watching TV or playing in front of the computer, is a frequent pastime for many adults," said Dr. Carol Greenwood, a senior author on the study and internationally renowned scientist in the field of nutrition and cognitive function in late life.

"This study addresses an additional risk associated with lifestyles that are highly apparent in North American populations."

With senior populations soaring, adopting a healthier lifestyle may help delay or prevent age-related cognitive decline, and is a way to give people some control over their brain function in later years, Greenwood said.