Around 7 million Americans ages 65 or older have dementia, and experts predict almost 12 million will by 2040. The cost in human suffering and medical care is staggering.

The good news is that each person has a great deal of control over how his or her brain health evolves over the coming decades. The Great Age Reboot lays out many ways — from nutrition and physical activity to brain games and meaningful friendships — that can protect your cognition.

Now two new studies clearly show how protecting your dental health, battling diabetes, and getting enough sleep can protect your brain power today and in the future.

One, published in the Journal of Diabetes Research, tracked 5,000 people over 12 years and found that both tooth loss and diabetes increase your risk for dementia. And when they happen together, the risk is even greater.

Fortunately, obtaining permanent teeth replacements (implants) seems to protect against cognitive decline associated with tooth loss. (Removable dentures don't do the trick, perhaps because of biofilm that forms on them).

And Type 2 diabetes is controllable — even reversible.

Another study, published in the American Journal of Preventive Medicine, reveals that people who are 65-plus and have trouble falling asleep in 30 minutes or who use sleep medication are at increased risk for dementia. Trouble falling asleep upped the risk of dementia by 51%; sleep-medication usage upped the risk 30%.

If that's you, increase your physical activity and interaction with friends, upgrade your nutrition, and see a sleep specialist pronto.