We know you love your comy couch or your favorite chair, but sitting for hours on end every day is doing your brain and body no favors. Everything from your memory to your muscles to your life span itself is being negatively affected by long stretches of inactivity.

“In my view, the inactivity associated with the couch is a major culprit in poor health,” says Charles E. Matthews, a senior researcher at the National Cancer Institute and the author of several studies on sedentary behavior and health.

Americans age 45 and over watch an average of four hours of television a day, and older adults, in particular, often spend up to half their free time in front of the tube. Your risk of serious illness goes up after about two hours of TV a day, Matthews says. Reducing that by even an hour a day and going for a brisk walk instead will help improve your health.

Here are some other ways in which too much couch time can be harmful.

1. Makes you forgetful

To put it simply, your brain loves it when you get regular physical activity. Moving around gets the blood flowing to your gray matter, which improves your memory and a number of other thinking skills, a recent Brazilian study found. Researchers tested a six-month exercise program on a group of sedentary but otherwise healthy older men, to see the effects on their blood flow and mental processes. The men sat for an average of nearly 12 hours a day — “A long time!” coauthor Hanna Karen Antunes, a professor of biosciences at the Universidade Federal de São Paulo, observed in an email. Her team found that exercise not only made a big difference in the men’s attitude — they had more vitality and slept better, she noted — but also resulted in a 21 percent improvement in their performance on memory tests, including markedly better planning and reasoning skills, attention, verbal memory and learning. And as their heart and lungs grew stronger from exercise, the participants experienced improved blood flow to the brain. “I tell older adults that exercise is like a pill,” Antunes said. “It makes you healthy, it’s low cost, and it’s easy.”

2. Affects your mood

Feeling down? It could be the hours you spend chained to your desk chair. In an Australian study, researchers observed nearly 3,400 government workers and found that the longer they sat during the day, the more likely they were to have moderate psychological distress, such as feeling nervous and hopeless. In particular, sitting more than six hours a day caused moderate distress among men and moderate to high distress among women, compared with workers who sat less than three hours a day. Consider this just one more reason to take a mood-lifting walk on your lunch break or a stress-relieving exercise class after work.

3. Spikes your blood sugar

Too much sitting around and not enough moving does a number on your blood sugar level, according to a 2017 University of Florida study. The findings show that a sedentary lifestyle is associated with an increase in blood sugar, even among adults who are at a healthy weight, putting them at risk for prediabetes or diabetes. Data from more than 1,000 slender adults indicated that those who reported getting little physical activity were more likely to have a blood sugar level of 5.7 or above, which is high enough to be considered prediabetes by the American Diabetes Association. A number of studies have linked high blood sugar to problems with thinking and memory.

4. Increases your risk for Alzheimer’s disease

Couch potatoes, beware: You could be increasing your risk of brain disease. Physical inactivity is one of the top seven risk factors for Alzheimer’s and the easiest one to do something about, according to a recent report in Lancet Neurology. Getting 20 minutes of vigorous activity three or more days a week, or even a 30-minute brisk walk five days a week, could help cut your risk of Alzheimer’s by 20 percent. Upping your physical activity would also help with the other risk factors, including high blood pressure, obesity and diabetes, researchers said.

5. Boosts your chance of dying early

Think exercising will save you? Not necessarily. Even if you exercise, sitting for long periods during the rest of the day can raise your risk of an early death, says Keith Diaz, assistant professor of behavioral medicine at Columbia University’s Department of Medicine and lead author of a recent study that looked at the effect of long, uninterrupted bouts of sitting. “We found that sitting for long periods of time increases your risk of death, regardless of whether or not you exercise,” Diaz said in an email. The good news: Those who took a movement break every 30 minutes (moving around for at least two minutes) lowered their risk of death. “The simple takeaway is, sit less, move more, and move frequently.”