Yet another reason to stress out about how much sleep you get: A new study shows that you can age your brain by up to seven years by getting too little sleep—or too much sleep. University of London scientists tested memory, reasoning, vocabulary, and other areas, and determined that between 7% and 8% of those who slept more than the recommended six to eight hours per night performed worse on every test except one. Meanwhile, a full 25% of women and 18% of men who slept less than the recommended amount also experienced a decrease in vocabulary and reasoning capacity.
Ultimately, researchers warn, getting the wrong amount of sleep increases mental and physical decline and can even lead to early death, the Daily Mail reports. "Adverse changes in sleep duration appear to be associated with poorer cognitive function in later-middle age," says a senior researcher. The study found that seven hours of quality sleep per night resulted in the highest scores, with six hours coming in second. Click to see how many Americans don't get enough sleep.