Call it aerobics for the brain.

Many of us assume that as we grow older, brain decline is inevitable, like gray hair and wrinkles. But a study published in the journal Neurology suggests that older adults can actually improve brain health after just six months of aerobic exercise.

And even couch potatoes who assume they are defenseless against time stand to benefit from these workouts.

The study followed 200 adults with an average age of 66 with no history of heart or memory problems. At the start of the study, these volunteers were given thinking and memory tests and an ultrasound that measured blood flow to the brain.

Then everybody took part in a supervised aerobics program three times a week. Participants started with 20-minute workouts, which were increased to an average of at least 40 minutes. Beyond that, they were asked to do aerobics on their own once each week.

After six months, tests measuring executive brain function — those mental processes that help us plan, focus and multitask — improved by almost 6%. Participants also saw a similar bump in verbal fluency, or the measure of someone’s ability to retrieve information, that was similar to what one might expect in someone five years younger.

Moreover, average blood flow to the brain ramped up nearly 3%.

The scientists acknowledge their work has some limitations. For example, the study group that exercised was not compared with a control group that did not. Researchers, however, tried to work around that shortcoming by testing people twice over six months before they launched the study.

Yes, Father Time can be a bear. But we aren’t utterly defenseless against his onslaught.