Sleep Is Not Linear: Reclaiming the Human Rhythm of Rest

Q1: Is it normal to wake up in the middle of the night?

Yes, and the evidence on this is clear. Brief awakenings between sleep cycles are a recognised feature of healthy sleep, as documented by the American Academy of Sleep Medicine.

Throughout the night, the brain moves through approximately 90-minute cycles, and short arousals at the transitions between these cycles are common. The problem does not lie in the waking itself, but in the anxiety it causes.

Recognising that these awakenings are a normal part of the sleep cycle is often the first step towards a more relaxed attitude towards night-time.

Q2: What is segmented sleep, and did humans naturally sleep in two phases?

Segmented sleep is defined as sleeping in two distinct periods, separated by an interval of quiet wakefulness.

Extensive research by historian Roger Ekirch into pre-industrial texts has revealed widespread references to 'first sleep' and 'second sleep' in medieval and early modern European cultures.

People would use the interval between the two periods of sleep for prayer, reflection, and quiet activity.

The consolidation of sleep into one continuous period appears to be a relatively modern development, largely shaped by the introduction of artificial light, which extended evening activities and altered the natural rhythm of the night.

Q3: How does my environment affect sleep quality?

Sleep evolved alongside specific environmental cues, such as gradual reductions in light intensity and colour temperature, a natural drop in ambient temperature, organic sounds and a sense of physical safety.

However, when your home environment replaces these cues with bright overhead LEDs, synthetic materials and visual complexity, your nervous system does not receive the biological signals it needs to begin the process of downregulation.

Research from Harvard Medical School has shown that blue-spectrum light from screens and artificial lighting can delay the release of melatonin by several hours. The sensory conditions of your bedroom are integral to sleep, not incidental.

Q4: What is orthosomnia, and could my sleep tracking be making things worse?

Orthosomnia is a term coined by sleep researchers to describe performance anxiety around achieving optimal sleep metrics, which is typically driven by wearable sleep-tracking devices.

There is a well-documented paradox: the more closely individuals monitor and attempt to optimise their sleep scores, the more hypervigilant and cognitively aroused they become at night.

This actively impairs the rest they are trying to achieve. While sleep trackers can offer useful insights over time, when they become the primary measure of a successful night, they often introduce an additional source of pre-sleep stress.

Q5: What governs when I feel sleepy, and why does it vary night to night?

There are two biological systems that regulate sleep timing. The first is the circadian rhythm, which is orchestrated by the suprachiasmatic nucleus in the hypothalamus and responds continuously to light, temperature and other environmental cues. The second is sleep pressure, which is generated by the accumulation of adenosine in the brain throughout the day.

Together, these systems produce an urge to sleep that behaves more like a tide than a switch. They respond to everything you experience, such as emotional stress, physical movement, light exposure and metabolic changes, which is precisely why your sleep varies from night to night. This variation is the system working as intended.

Q6: Can interior design support better sleep?

It can, and the evidence base for this is growing.

Research in environmental psychology and neuroscience consistently shows that the sensory qualities of a space—such as its lighting, temperature, texture, colour scheme and acoustic properties—either support or inhibit the nervous system's ability to relax.

A bedroom deliberately aligned with circadian biology and nervous system needs creates conditions that allow sleep to come more naturally.

Q7: I sleep lightly and always have. Does that mean something is wrong with me?

Not necessarily. Sleep architecture is influenced by genetics, neurological profile, life stage, hormonal status and environmental conditions.

What is perceived as light or fragmented sleep is often an appropriate nervous system response to an environment that has not yet provided the sensory conditions necessary for deeper rest.

While it is understandable to interpret light sleep as a personal failure, this is rarely accurate. Addressing the environmental and contextual factors around sleep can produce measurable shifts without any change to the individual.