There's no surefire way to keep dementia at bay, but there are steps you can take to dramatically slash your risk -- including the following lifestyle changes you can make, starting today.

Start by getting a little more movement. Physical inactivity may be responsible for up to 21 percent of all U.S. dementia cases -- making it the leading lifestyle-based cause of the disease.

You don't have to sweat yourself silly or even join a gym. Just take up a hobby that involves getting out and getting active: tennis, gardening, or even something as simple as a brisk walk every evening.

The other lifestyle factors, in order of impact on dementia risk, are low education, smoking, depression, hypertension, diabetes, and obesity.

You may not be able to do much about that degree you never earned, but all the others are within your control. And since they carry plenty of other risks even without throwing dementia into the mix, there's no reason not to make those changes starting today.

Sleep apnea is another major dementia risk factor. When researchers looked at data on 298 senior women who were tracked for five years, they found that those who battled apnea were 85 percent more likely to battle cognitive decline by the end of the study period than those without it.

Since sleep apnea is often caused by obesity, here's a golden opportunity to slash your dementia risk: Lose the weight and get your apnea under control through diet and exercise, and you'll knock three risk factors off the list at once – and get a whole lot healthier in the process.

Not a bad deal at all.

P.S. Simple B vitamins can slow or even stop the brain shrinkage linked to dementia. Learn more about it for free right here.