Chapter 2: Get your circadian rhythm on track – with light as your ally

Your body is controlled by light. Every cell, every hormone and almost every process in your body follows a circadian rhythm. But for the system to function optimally, your brain needs to know exactly what time it is. The best way to tell it? Natural light during the day and darkness at night. This week is about using light strategically: more of the right light at the right times, and less artificial lighting that disrupts your natural rhythm.

Try these habits all week long – they also reinforce your sleep habits from Week 1:

1. Natural morning light (10–20 minutes) Get daylight within 30 minutes of waking up. Go outside (even on cloudy days). Avoid sunglasses, glasses or contact lenses for the first few minutes – let the light hit your eyes directly.
2. Fixed wake-up time (±30 minutes) Keep your wake-up time stable, even on weekends. Your sleep actually begins in the morning.
3. Dim the lights 2 hours before bedtime Use lamps at eye level with warm tones and low lighting. Avoid white ceiling spotlights.
4. Screen filter after sunset Activate a red night filter on all your devices – not just "night mode," but a filter that really blocks blue light.

How to measure progress: Take 10 seconds each morning to note:

• Morning light (minutes): ___
• Evening light dimmed: ✔/✖
• Energy level at 10 a.m. and 3 p.m.: 0–10
• Sleep quality: 0–10

 

Halfway there: Light hacks that make it easy

Are you halfway there? If you've been getting morning light and sticking to your wake-up time, the evening will automatically become easier – your body will start to expect sleep.

Quick status update:

• Did you get morning light for 3 days in a row?
• Was the evening light really dimmed?

Continue with the basics and choose 1–2 expert tips if you want to optimise further:

Expert tips (choose 1–2)

1. Blue-light blockers (BLB) Glasses with 100% blue-blocking lenses (amber/red) from at least 3 hours before bedtime. Combine with full "night mode" on screens.
2. Lux measurements and light remediation at home
• In the morning: Aim for ≥1000 lux in the eyes (outdoors).
• In the evening: Keep lighting below 30 lux in the living room and bedroom. Replace 2–3 lamps with warm 2700K bulbs with low lumen, placed at eye level.
3. The sunglasses rule No sunglasses during the day. Natural light is always welcome in your eyes – let it in!

Troubleshooting and tips

• Can't fall asleep? Probably too much evening light or screen time. Dim the lights earlier.
• Tired in the morning? Get more morning light (even on grey days) and stick to your wake-up time.

Avoid:

• Skipping morning light, even if it's cloudy.
• Using screens without a filter after sunset.