For the study, researchers examined diet and exercise data for about 9,000 adults who were 51 years old on average and had no history of dementia. Participants performed treadmill tests to assess what’s known as cardiorespiratory fitness, or how easily the circulatory and respiratory systems can supply oxygen to muscles during physical exertion. Scientists used a standard measurement known as metabolic equivalents (METs) which reflects how much oxygen is consumed during physical activity.
Study participants also completed food questionnaires detailing what they ate on three days within one week. Scientists then rated their eating habits based on how closely people followed two diets that can promote both heart and brain health: the Dietary Approaches to Stop Hypertension (DASH) diet and the Mediterranean diet.
Over an average follow-up period of about nine years, about 1,500 people developed dementia. Following a DASH or Mediterranean diet didn’t appear to impact dementia risk, according to findings published in the International Journal of Behavioral Nutrition and Physical Activity.
However, each 1-MET increase in exercise capacity demonstrated during treadmill tests was associated with a 5 to 6 percent lower risk of developing dementia.
“This study confirms the results of prior studies that suggest nothing is more important to reduce one’s risk of dementia than aerobic exercise,” says Andrew Budson, MD, a professor and associate director of the Alzheimer’s Disease Research Center, at Boston University, who wasn’t involved in the new study.
The Study Had Some Limitations
The new study wasn’t designed to prove whether or how exercise or eating habits might directly impact brain health. One limitation of the study is that researchers only looked at eating habits over a three days, and only looked at exercise capacity at a single moment in time. It’s possible that participants’ habits shifted over time in ways that weren’t measured in the study and impacted their dementia risk.
Another drawback of the study is that researchers relied on participants to accurately recall and report on the foods they consumed, making it possible that people may have provided inaccurate or incomplete results. By contrast, scientists objectively measured exercise capacity using treadmill tests.
Any Amount of Exercise Benefits the Brain
The new study findings add to the evidence suggesting that exercise may be one of the most important things to focus on when it comes to promoting brain health as you age, says Mika Kivimaki, PhD, a professor and chair of social epidemiology at University College London in England, who wasn’t involved in the new study.
“The biggest drop in dementia risk happens when people move from being completely sedentary to engaging in some form of physical activity,” Dr. Kivimaki says. “Studies that track physical activity levels from midlife into old age show clear benefits of staying active over time. However, being active at any age seems to have a positive impact on cognitive health, so it’s never too late to start.”
