A broken sleep schedule affects mood, focus, metabolism, and immune function. The good news: the circadian system is highly responsive to the right inputs, and meaningful improvement within a week is achievable. How Your Sleep Schedule Gets Broken The circadian rhythm is the body's approximately 24-hour internal clock, regulated primarily by the suprachiasmatic nucleus (SCN) in the hypothalamus. It coordinates the timing of sleep, wakefulness, temperature, hormone release, digestion, and dozens of other biological processes. The circadian rhythm is calibrated…