What should be reduced before bedtime to support circadian rhythm?

• A. Exercise and hydration
• B. Noise and movement
• C. Light exposure and screen time
• D. Breakfast timing

Answer: (C)

Light-dark cues drive our circadian rhythm, with darkness signaling the body to prepare for sleep. Reducing light exposure and screen time before bed helps melatonin rise at the right time, making it easier to fall asleep and sleep more deeply. Screens emit blue light, which strongly suppresses melatonin, so dimming lights and avoiding or filtering screen use in the evening reinforces the natural night signal and supports a regular sleep-wake pattern.

To put this into practice, use dim or warm lighting in the evening, limit phone, computer, and TV use at least an hour or two before bedtime, and consider blue-light filters or glasses if you must use screens. Keep the bedroom dark and comfortable to strengthen the sleep signal.

Other factors can affect sleep but don’t directly cue the circadian clock in the way evening light does. Exercise and hydration influence how sleepy you feel and your overall sleep quality, but intense activity close to bedtime can increase arousal and delay sleep. Noise and movement can disrupt sleep once you’re trying to rest, rather than helping the clock align. Breakfast timing affects circadian alignment more broadly as a morning cue, not as a direct signal to quiet the mind before sleep.