Sleep check

1. Which single input has the largest influence on when you feel sleepy?

Light is the primary signal that resets your internal clock. Morning light pulls it earlier, evening light pushes it later.

2. Roughly what bedroom temperature suits most sleepers?

Core temperature has to fall for sleep to start, so a cooler room than most people keep - roughly 16 to 19 degrees - helps.

3. You wake at three in the morning and are still awake twenty minutes later. What should you do?

Getting out of bed prevents your brain learning that bed is where you lie awake. It feels wrong and it is the most effective behavioural step.

4. After a badly broken night, what should you do the next morning?

Sleep pressure builds from your wake time. Lie-ins reduce the pressure available for the next night, which is how one bad night becomes a pattern.

5. Which tracker number should you trust least?

Stage breakdown is inferred from movement and heart rate and compares poorly against laboratory measurement - and it is the number apps highlight most.

6. You are flying east for a two-day trip. What does the course recommend?

For trips under about three days, adjusting costs more than it returns. Stay on home time and plan around it.