A long-term aerobic exercise program beginning (at latest) in mid-life may prevent structural deterioration in the brain occurring with age, suggests a new study conducted on mice. Cardio, turns out, is your friend.

“Aging is frequently accompanied with frailty and cognitive decline,” wrote the authors. “In recent years, increasing evidence has linked physical inactivity with the development of dementias such as Alzheimer’s disease.”

But what are the biological reasons exercise combats cognitive decline? To find out, the researchers designed an animal study that made use of a variety of techniques and tools, including RNA sequencing, fluorescence microscopy, and electron microscopy. When a group of mice reached an age equivalent to a middle-aged human (12 months), the researchers provided them with a running wheel and then assessed their brains when the rodents reached an age roughly equivalent to 60 in humans (18 months).

Throughout the experiment, the mice ran about 2 miles per night. As they grew older, this physical activity noticeably improved their motivation and ability to participate in behaviors that are typically affected in a negative way by aging. The researchers also observed how exercising significantly reduced age-related pericyte loss in the outer layer of the brain.

Why is this important? Pericytes are one of two interacting cell types that compose blood vessels. Endothelial cells form the inner lining of the vessel wall, while pericytes envelop the surface of the vascular tube. Pericytes help control vascular morphogenesis and help regulate the stability of your cardiovascular system. They play a role in the blood brain barrier as well. Exercise, the study results demonstrated, also improved other indicators of dysfunction in the vascular system and blood-brain barrier in the mice.

Importantly, the beneficial effects of exercise were not seen in mice deficient in the Apoe gene. Certain variants, though not others, of Apoe are known to be a major genetic risk factor for late-onset Alzheimer’s. Ordinarily in mice, Apoe expression in the outer layer of their brains declines as mice age, yet exercise prevented this, the researchers reported.

“More than five million people in the United States suffer from Alzheimer’s disease, and this is expected to exceed 10 million in the next 20 years,” wrote the authors. “In order to prevent and treat age-related neurodegenerative diseases, particularly Alzheimer’s, it is essential to better understand the factors that contribute to aging-induced susceptibility.”

Certainly, for anyone who fears the erosion of their memories, a simple program of daily aerobic exercise, as suggested by this animal study, might be the simplest way to take a stab at preventing Alzheimer's disease. If nothing else, you will greet old age in the best possible health.

Source: Soto I, Graham LC, Richter HJ, et al. APOE Stabilization by Exercise Prevents Aging Neurovascular Dysfunction and Complement Induction. PLoS Biol. 2015.