If you're one of those people with a long PER3 gene, don't fret. Instead, perhaps you should chug coffee, which will keep you alert and help reverse memory loss.

Researchers at the University of South Florida examined 55 mice bred to have symptoms of Alzheimer's disease. Half of the mice drank regular water while the other half drank caffeine-infused water (they were give about 500 milligrams of caffeine, the equivalent of five cups of coffee per day for a human). After two months, the caffeinated mice had a 50 percent reduction in their levels of beta amyloid proteins, which tangle in the brain. These tangled proteins are thought to cause the memory loss and confusion in Alzheimer's disease. Further tests indicate that caffeine affects the production of enzymes that cause beta amyloid proteins. "The results are particularly exciting in that a reversal of pre-existing memory impairment is more difficult to achieve," says Gary Arendash, who led the study. "That's important because caffeine is a safe drug for most people, it easily enters the brain, and it appears to directly affect the disease process."

But the researchers warn that people should not begin using caffeine supplements in the hopes to ward off Alzheimer's. "Caffeine reverses cognitive impairment and decreases brain amyloid-β levels in aged Alzheimer's disease mice."

[Further reading: Journal of Alzheimer's Disease]