Imagine spending hours on the couch, feeling good about the morning’s workout. You ran, you lifted, you stretched. You believe you’ve done enough to protect your health. But new research says that may not be true.

Sitting for extended periods, regardless of exercise, can harm the brain. Even the most active older adults face the risk of faster brain shrinkage if they sit too much.

The study, led by researchers from Vanderbilt University’s Memory and Alzheimer’s Center, tracked older adults for seven years. They examined how long participants sat, how often they moved, and how much their brains shrank over time.

The results were troubling. Exercise didn’t fully counteract the effects of prolonged sitting. The more hours spent sitting, the greater the brain decline.