Certain changes in the brain are inevitable as you age: The prefrontal cortex and the hippocampus, both of which are important for memory, planning, and learning, begin to shrink. Some of the myelin-covered axons that you spent the first half of your life developing may begin to degrade, and blood flow in the brain can decrease as arteries narrow. However, the healthier you keep your body and the more you challenge different sections of your brain, the longer you can keep it functioning well, . "When people engage the parts of their brain that are still healthy, they can help push back the more severe cognitive loss by two to three or even five years,

HEIGHTENED RISKS: Risk for Alzheimer's disease and other forms of dementia increases at this stage, as well as risk of stroke. One in nine people over age 65 develop Alzheimer's disease, and by the time you turn 85, the risk is one in three. As your body becomes frail, you also increase your risk for falls, which can jeopardize brain health.

Brain-Savvy Strategies

• • Call at least one friend a day. The more friends and family you keep in touch with, the more outlets you'll have to exercise your brain in conversation, and the more opportunities you'll have to participate in stimulating activities. In fact, a Dutch meta-analysis published in 2015 in Ageing Research Reviews found that low social participation, less frequent social contact, and loneliness were comparable to other well-known risks of dementia, including physical inactivity and late-life depression.
• Get smartphone savvy. While too much technology can be detrimental to the developing brain, learning how to call an Uber so you can attend a lecture at your library, playing trivia games on your phone, or learning how to share photos of your grandchildren on Facebook can be an important tool in staying socially and mentally active, says Dr. Small.
• Do something different once a week. "In retirement, people often go on autopilot,". "They have the same lunch every day, celebrate their birthday at the same restaurant with the same people every year." But by innovating in little ways—exploring a new city, a new part of town, or a new recipe, for example—you may be able to stimulate norepinephrine, a powerful neurotransmitter that, among other things, increases motivation, alertness, and speed and retention of learning, 
• Walk it out. Research from the University of Maryland published in 2015 in the Journal of the International Neuropsychological Society found that moderate exercise such as walking helped to reverse shrinking of the brain's outer layer in both healthy seniors and those with mild cognitive impairment. Even walking as little as 15 minutes a day can help, . Strength training is also important in maintaining brain health, so if you're wheelchair-bound, enroll in a seated exercise class.
• Keep your home safe. Falls are the leading cause of traumatic brain injury, and the risk of a fall greatly increases after age 75. Make sure you aren't on any medications that make you dizzy, that your eyeglass prescription is up-to-date, and check your home for tripping hazards such as cords, throw rugs, and loose railings.
  
  Adults with mild cognitive impairment who sustained head trauma had a higher level of amyloid deposits than those who did not report head injuries, demonstrating a possible link between brain injury and the development of Alzheimer's disease, according to a Mayo Clinic study published in 2013 in Neurology.