CIRCAL ist ein Nahrungsergänzungsmittel mit mikroverkapseltem Koffein. Die Kapsel hat drei Schichten, die das Koffein mit einer Verzögerung von 3 oder 8 Stunden freisetzen.

Wie funktioniert die verzögerte Freisetzung?

CIRCAL nutzt Mikroverkapselung — dasselbe Verfahren, das in der Pharmazie seit Jahrzehnten für Retard-Medikamente eingesetzt wird. Eine pH-sensitive Schutzhülle umgibt den Koffein-Kern und löst sich zeitversetzt auf.

Wieviel Koffein enthält eine Kapsel?

Jede Kapsel enthält 100mg Koffein — das entspricht etwa einer Tasse Filterkaffee.

Was ist der Unterschied zwischen CIRCAL8 und CIRCAL3?

CIRCAL8 hat eine 8-stündige Verzögerung und ist für die Nacht konzipiert. CIRCAL3 hat eine 3-stündige Verzögerung und eignet sich für kürzere Pausen.

Ja. Die Kapselhülle besteht aus pflanzlichem Polymer. CIRCAL ist 100% vegan.

Night Shift: 50 Percent Higher Risk of Sleep Disturbance

The Number You Should Know

Imagine flying from London to Cairo every Monday — and back every Friday. Without ever adjusting to the time zone. Five days of jetlag, two days of recovery, then repeat.

That sounds absurd. But it describes, with remarkable accuracy, what millions of shift workers experience. Every week.

A 2026 analysis of cross-sectional data from the UK Biobank — involving roughly 285,000 participants — has quantified the association between shift work and sleep disturbance at a scale never seen before. The central finding: permanent night shift workers have a 50 percent higher risk of sleep disturbance, defined by insomnia and excessive daytime sleepiness (adjusted odds ratio: 1.50).

What the Study Shows

The researchers distinguished between three shift patterns and compared them with non-shift workers. All patterns showed elevated odds ratios — but the gradient is revealing:

Shift work without nights → OR 1.21
Occasional night shifts → OR 1.37
Permanent night shifts → OR 1.50

In total, 42,181 participants (14.8 percent) met the criteria for sleep disturbance. The association was strongest among individuals under 55 and — surprisingly — among non-smokers. The authors speculate that smokers may experience a stimulant-based compensation from nicotine that dampens subjective sleep disturbance scores.

Surprising indeed. Smoking as an accidental counterweight to night-shift fatigue. Sometimes irony writes itself.

Why Do Night Shifts Hit Sleep Twice?

What the UK Biobank captures in numbers has a concrete neurobiological mechanism — one that connects directly to what we know about sleep inertia.

The problem operates on two layers:

Layer 1: Sleeping against the circadian phase. The body has an endogenous rhythm governed by the suprachiasmatic nucleus (SCN). This rhythm dictates when melatonin is secreted, when core body temperature bottoms out, and when cortisol surges in the morning. Night shift work forces the body to sleep during its biological wake phase and work during its biological sleep phase.

The result: daytime sleep after a night shift is on average 1 to 4 hours shorter than nighttime sleep — not because of an alarm, but because light, cortisol, and body temperature tell the brain: "Time to wake up."

Layer 2: Waking at the circadian trough. Workers who need to rise for an evening shift often wake during a phase when circadian alertness is at its lowest. For evening chronotypes, the temperature nadir falls around 6:00 AM — but for a 10 PM night shift that requires waking at 2 or 3 PM, the cortisol awakening response is almost entirely absent.

The consequence: prolonged sleep inertia, measurable cognitive impairment, and a brain that cannot cleanly complete the transition from sleep to wakefulness. A 2019 study in Scientific Reports on hospital staff found that shift workers show significantly higher sleepiness and lower attention scores than day workers — with the effect strongest in the first hour after waking.

What Research Knows About Countermeasures

Two approaches have shown measured effects in controlled studies:

The Caffeine Nap

A pilot study (Centofanti et al., 2020, Chronobiology International) tested a combination of 200 mg caffeine and a 30-minute nap during a simulated night shift. The result: the combination showed measurably stronger effects on vigilance and subjective fatigue in the 45 minutes post-nap than either caffeine or napping alone.

The mechanism is pharmacologically elegant: caffeine takes 20 to 30 minutes to reach peak plasma concentration. A nap of exactly that duration avoids entry into deep sleep (and the resulting sleep inertia upon waking) — and by the time you wake, the caffeine has already blocked the adenosine receptors.

A meta-analysis (Prehospital Emergency Care, 2018) confirmed: caffeine alone measurably decreases attention lapses in shift workers — but simultaneously worsens sleep quality and sleep duration. Timing matters, not just dose.

Biodynamic Lighting

The German DGUV project "Licht und Schicht" (2021–2023) investigated the effect of dynamic workplace lighting on industrial shift workers. Initial results published in 2024: the nighttime lighting intervention showed signs of higher melatonin levels and lower cortisol levels at the end of the night shift. Leisure-time light recommendations led to longer sleep durations during early shifts.

The project matters because it demonstrates: light is the strongest zeitgeber that shift workers can control — and targeted light interventions have measurable physiological effects.

What This Means

According to Eurostat, approximately 15 percent of workers in Germany work shifts — over six million people. Around 4.6 percent work regular night shifts. In nursing, hospitals, logistics, manufacturing.

The UK Biobank data show that sleep disturbance rates rise with night-shift intensity — dose-dependent, adjusted, in a cohort large enough to control for confounders.

This is not an alarmist headline. It is data. And the data says: permanent night work means permanently living against your own biological clock. The consequences are measurable — in sleep architecture, in cognitive performance upon waking, and in the sleep inertia that systematically impairs the transition from sleep to wakefulness.

The question is not whether night shifts disrupt sleep. The question is what society does about it.

Sincerely curious,
Lena Wachmann