It's a common scenario: It’s midafternoon and you’re in a slump, with no motivation to press on with your work. At that point—or any point, you feel tired—a good question to ask yourself is: Am I sleepy or fatigued? We often use those words interchangeably, but physiologically speaking, they describe different conditions. And figuring out which condition is at play...

As we try to cram more and more activities into our lives, we may feel that the time we spend sleeping is somehow wasted, and wonder if we really need seven to nine uninterrupted hours per night.

If you’ve noticed that your need for sleep has lessened as you age, or if you have more trouble sleeping than you used to, take heart: Some changes to sleeping patterns are part of the normal aging process.

If you’ve ever been cheered by a sunny day or felt gloomy on a cloudy one, it will probably come as no surprise that light has a powerful effect on our sleep cycle, mood, and overall well-being.