Circadian Rhythms and Ageing

How the body keeps time, why this rhythm changes with age, and why restoring alignment is central to longevity

Ageing is often described in years, biomarkers, or visible changes. Yet one of the most subtle and profound shifts that occurs over time is temporal. The body’s relationship with time changes.

Long before disease appears, before fatigue becomes chronic or sleep feels fragile, the internal rhythms that once moved with clarity and contrast begin to soften. Day and night lose definition. Energy peaks flatten. Recovery becomes less automatic. These changes are not random. They reflect a gradual alteration in the circadian system, the biological network that governs how the body organises time.

At Clinique La Prairie, circadian rhythms are understood as a foundational element of longevity. They influence not only sleep, but metabolism, hormonal balance, immune activity, cardiovascular health, cognitive clarity, and emotional regulation. In our proprietary model of mental health and wellbeing, circadian rhythms and sleep recovery sit at the base of the structure, because they condition nearly every other function.

This article explores circadian rhythms through the lens of ageing and healthspan. It examines how the body keeps time, how this timing system evolves with age, why circadian disruption accelerates functional decline, and how restoring alignment can support longevity. Sleep is addressed not as an isolated topic, but as one of the most visible expressions of circadian health.

The biology of time: what circadian rhythms are

Many functions in the human body follow natural cycles that last approximately 24 hours. These cycles regulate processes as diverse as hormone secretion, body temperature, metabolism, cardiovascular activity, immune responses, and sleep–wake patterns. They are known as circadian rhythms.

Circadian rhythms are endogenous biological oscillations that allow organisms to anticipate and adapt to the daily light–dark cycle generated by the Earth’s rotation. Rather than reacting passively to the environment, the body prepares in advance. Energy is mobilised before waking. Hormones rise before activity. Repair processes intensify before sleep.

This anticipatory design is essential for efficiency and resilience. A body that can predict what comes next expends less energy correcting errors. Over a lifetime, this efficiency matters.

The suprachiasmatic nucleus: the master synchroniser

Circadian rhythms are coordinated by a central biological clock located deep in the brain. This structure, known as the suprachiasmatic nucleus, sits in the hypothalamus and acts as the master synchroniser of the circadian system.

The suprachiasmatic nucleus receives direct input from the retina, allowing it to detect environmental light and darkness. With this information, it estimates the time of day and aligns internal rhythms with the external world. This alignment is then communicated to peripheral clocks distributed throughout the body.

Circadian clocks exist in nearly every organ, including the liver, kidneys, heart, lungs, muscles, and gastrointestinal system. Each of these clocks regulates local functions such as glucose metabolism, detoxification processes, immune activity, and tissue repair. The role of the central clock is to ensure coherence between them.

When the central clock and peripheral clocks are synchronised, physiology functions as an integrated system. When synchronisation weakens, organs may operate on conflicting schedules. This internal desynchrony is increasingly recognised as a contributor to metabolic dysfunction, inflammation, and accelerated ageing.

Circadian rhythms as a foundation of longevity

Longevity is not simply about extending lifespan. It is about preserving function, resilience, and adaptability across time. Circadian rhythms support all three.

Stable circadian rhythms help regulate energy production, optimise metabolic efficiency, and create predictable windows for cellular repair. They also support hormonal balance, immune regulation, and cardiovascular stability. Importantly, circadian rhythms influence the nervous system, shaping mood, stress tolerance, and cognitive performance.

In Clinique La Prairie’s model of mental health and wellbeing, circadian rhythms and sleep recovery are considered foundational elements. They influence multiple downstream hallmarks, including resilience to stress, vitality, neuro-immune health, cardiovascular health, cognitive clarity, and positive emotionality.

This positioning reflects a core principle. When circadian rhythms are disrupted, other interventions become less effective. When rhythms are restored, multiple systems often improve simultaneously.

How circadian rhythms change with ageing

Ageing affects nearly every physiological system, and circadian rhythms are no exception. However, the changes are often subtle and gradual, making them easy to overlook.

Research shows that, compared to younger adults, older adults exhibit a reduction in the amplitude of circadian rhythms. The daily fluctuations in waking activity, body temperature, cortisol, melatonin, and plasma glucose become shallower. The contrast between day and night diminishes.

This loss of amplitude means that biological signals are less distinct. The body still follows a rhythm, but with reduced clarity. The internal cues that once strongly signalled activity or rest become quieter. Over time, this can impair the ability of organs to coordinate effectively.

These changes may contribute to alterations in sleep patterns, appetite regulation, glucose metabolism, and immune function commonly observed with ageing. They also help explain why recovery from stress or illness may take longer later in life.

Circadian rhythms, ageing, and metabolic health

Circadian rhythms play a critical role in metabolic regulation. Glucose metabolism, insulin sensitivity, and lipid processing all follow daily patterns influenced by circadian clocks.

With ageing and circadian flattening, these metabolic rhythms can become dysregulated. Plasma glucose variations between day and night may narrow, but this does not necessarily reflect improved control. Instead, it may indicate reduced metabolic flexibility.

Reduced circadian amplitude has been associated with impaired glucose regulation and increased metabolic vulnerability. Over time, this may contribute to insulin resistance, chronic inflammation, and cardiovascular risk, all of which are key determinants of healthspan.

From a longevity perspective, maintaining circadian integrity supports metabolic resilience. It allows the body to efficiently switch between energy utilisation and storage, and between activity and repair.

The circadian system and the immune response

Immune function is also rhythmic. The activity of immune cells, the release of cytokines, and inflammatory responses vary across the day and night.

Healthy circadian rhythms support a balanced immune response, allowing effective defence without chronic activation. Disruption of circadian rhythms, particularly when sustained, can tilt the immune system toward persistent low-grade inflammation.

Neuro-immune interactions are especially relevant in ageing. Chronic inflammation has been identified as a key driver of age-related decline and neurodegeneration. Circadian misalignment may exacerbate this process by impairing the timing and resolution of immune responses.

Supporting circadian rhythms is therefore not only about sleep quality, but about preserving immune balance and reducing inflammatory load over time.

Sleep as an expression of circadian health

Sleep is one of the most visible manifestations of circadian rhythms. It reflects how effectively the internal clock coordinates rest and recovery.

Sleep follows a structured architecture composed of repeating cycles that include three non-rapid eye movement stages and one rapid eye movement stage. These cycles typically last around 90 minutes and repeat several times per night.

Deep non-REM sleep supports physical restoration, immune activity, and growth hormone release. REM sleep supports cognitive and emotional processing. Together, these stages contribute to brain health, memory consolidation, and emotional regulation.

With ageing, sleep often becomes lighter and more fragmented. Older adults may take longer to fall asleep, wake more frequently during the night, and spend less time in deep slow-wave sleep. These changes are closely linked to alterations in circadian rhythms.

It is important to distinguish between occasional poor sleep and sustained circadian disruption. A single night of disturbed sleep is rarely harmful. However, persistent circadian misalignment and sleep fragmentation can impair restorative processes over time.

Circadian rhythms, sleep, and brain health

One of the most compelling links between sleep and longevity involves the brain’s waste-removal system, known as the glymphatic system.

During deep sleep, the brain increases the clearance of metabolic waste products. Cerebrospinal fluid circulates more freely, washing away substances such as beta-amyloid and tau proteins, which have been associated with neurodegenerative diseases.

This process is significantly more active during sleep than during wakefulness. When deep sleep is reduced or fragmented, glymphatic clearance may be less effective. Over decades, this may contribute to increased neurodegenerative risk.

Sleep disturbances have been identified as a risk factor for dementia. Long-term observational studies show that chronically short sleep duration is associated with increased risk of cognitive decline and cerebrovascular disease.

These findings reinforce the idea that circadian rhythms and sleep recovery are integral to brain longevity, not merely comfort or mood.

Hormonal rhythms and stress regulation

Circadian rhythms regulate the secretion of key hormones, including cortisol and melatonin.

Cortisol follows a daily pattern, peaking in the morning to support alertness and energy mobilisation, and declining at night to allow rest. Melatonin rises in the evening, signalling the body to prepare for sleep.

With circadian disruption or ageing-related flattening, these hormonal rhythms may become dysregulated. Elevated nighttime cortisol can interfere with sleep onset and maintenance, while blunted melatonin rhythms can weaken sleep signals.

Chronic dysregulation of stress hormones contributes to inflammation, metabolic disturbances, and cardiovascular strain. Supporting circadian rhythms helps preserve the natural oscillation between activation and recovery.

Measuring circadian and sleep health

Circadian disruption often develops gradually, making subjective perception unreliable. Individuals may normalise fatigue, fragmented sleep, or reduced vitality as inevitable consequences of ageing or lifestyle.

For this reason, structured assessment is essential. At Clinique La Prairie, sleep recovery and circadian-related behaviours are evaluated as part of the Wellbeing Index Assessment. This includes detailed exploration of sleep duration, sleep latency, nocturnal awakenings, environmental factors, cognitive arousal, and daytime consequences such as sleepiness or lack of restoration.

Assessment provides clarity. It transforms vague discomfort into actionable insight.

Supporting circadian rhythms across the lifespan

Circadian rhythms are not fixed. They respond to behavioural, environmental, and physiological cues. Several non-pharmacological interventions have been shown to support circadian health.

Consistent daily routines anchor the circadian system. Waking and sleeping at stable times reinforces temporal signals. Daytime exposure to natural light strengthens alignment between the central clock and the environment. Reducing evening light exposure, particularly from screens, protects nocturnal signalling.

Physical activity supports circadian amplitude when appropriately timed. Regular movement enhances vitality and supports metabolic rhythms, while excessive late-evening exertion may delay sleep.

Nutrition timing also plays a role. Evening meals that are light and early support nocturnal metabolic downregulation, while heavy or late meals can interfere with circadian coordination.

Stress management is essential. Psychological stress acts as a circadian disruptor by elevating arousal and altering hormonal rhythms. Practices such as mindfulness, paced breathing, and relaxation techniques help restore autonomic balance and support sleep recovery.

At Clinique La Prairie, chrononutrition principles and targeted nutraceuticals are used to support circadian alignment. Nutrition is structured to enhance alertness and focus during the day while promoting calm and restoration in the evening. Targeted nutraceuticals with nootropic and calming properties may gently support circadian regulation without overriding physiological processes.

Circadian rhythms, ageing, and the opportunity for recalibration

Ageing does not eliminate the circadian system, but it changes its expression. The softening of rhythms may reduce resilience, making the body more sensitive to stressors, irregular schedules, and environmental disruption.

However, the circadian system remains responsive. Evidence shows that circadian rhythms and sleep recovery are actionable. Through consistent routines, environmental alignment, movement, nutrition, and stress regulation, circadian coherence can be strengthened even later in life.

From a longevity perspective, this represents an opportunity. Supporting circadian rhythms is not about reversing age, but about preserving functional clarity across time.

From circadian health to mental wellbeing

Circadian rhythms do not operate in isolation from mental health. They are deeply intertwined with emotional regulation, stress resilience, cognitive performance, and social functioning.

Disrupted circadian rhythms are associated with mood disorders, anxiety, and reduced stress tolerance. Conversely, restoring rhythm often improves emotional stability and cognitive clarity.

In Clinique La Prairie’s framework, mental wellbeing is understood as more than the absence of disorder. It includes positive psychosocial functioning, vitality, cognitive focus, and emotional balance. Circadian rhythms and sleep recovery are foundational to this state.

Restoring rhythm as a pathway to wellbeing

Circadian rhythms are the body’s internal architecture of time. They coordinate physiology, guide recovery, and support resilience across the lifespan. With ageing, these rhythms may lose amplitude, becoming quieter and less distinct. Sleep may fragment. Recovery may slow.

Yet circadian health remains one of the most powerful levers for longevity. By restoring alignment between internal clocks and the external world, it is possible to support metabolic stability, immune balance, brain health, and emotional regulation.

At Clinique La Prairie, circadian rhythms and sleep recovery are approached as part of a broader vision of mental health and wellbeing. They form the foundation upon which resilience, vitality, cognitive performance, and positive emotionality can emerge.

For those who feel that their rhythm has faded, or who sense a growing distance between effort and recovery, addressing circadian alignment can be the beginning of a deeper recalibration. This understanding guides our approach to mental wellbeing optimisation and finds its most comprehensive expression in Life Reset, a program designed to support mental and physical thriving through structured, science-based, and holistic care.

Longevity, in this sense, begins with time.