The widely held belief that ageing only becomes a concern after turning 50 is fundamentally wrong, according to molecular biologist Dr Marion Gruffaz, who warns that cellular deterioration begins much earlier – in the late thirties.
Dr Gruffaz, who holds a doctorate from University Lyon I/Paris V and completed postdoctoral research in cancer biology at the University of Southern California, says the molecular processes that drive accelerated ageing are already underway long before most people start paying attention. “At the molecular level, the processes that drive accelerated ageing, including NAD+ decline, the buildup of senescent cells, and the gradual breakdown of protein quality control, all begin in the late 30s,” she said. “Waiting for symptoms is the single biggest error.”
The hidden onset of ageing
Scientific research supports the idea that ageing is a complex biological process starting far earlier than commonly assumed. Senescent cells – cells that have stopped dividing but remain metabolically active – accumulate with age, promoting inflammation and disrupting tissue function. The immune system’s ability to clear these cells declines over time, worsening the problem. At the same time, cells lose their capacity to maintain protein quality control, leading to a buildup of damaged and misfolded proteins, a primary hallmark of ageing implicated in neurodegenerative conditions such as Alzheimer’s disease.
Biological age, distinct from chronological age, can be measured through biomarkers including DNA methylation patterns, telomere length, inflammatory markers and metabolic health indicators. These measures show that lifestyle choices made in the thirties and forties have a direct impact on how quickly cells age.
The sleep deficit that ages you
Beyond the timing of cellular decline, Dr Gruffaz identifies persistent mild sleep deprivation as an everyday habit whose effects are drastically underestimated. She is not referring to clinical insomnia but to the common practice of cutting rest short by an hour or so each night.
“During deep sleep, the brain’s glymphatic system clears the metabolic waste that accumulates in neurons throughout the day,” she explained. “Disrupting that process repeatedly accelerates neuroinflammation and has measurable effects on biological age markers.”
The glymphatic system acts as the brain’s waste-clearance pathway, primarily active during slow-wave sleep. It removes potentially harmful proteins such as beta-amyloid and tau, which are linked to Alzheimer’s disease. During sleep, the brain’s extracellular space expands, reducing resistance to fluid flow and facilitating waste removal. When sleep is insufficient or disrupted, this clearance slows, leading to increased neuroinflammation characterised by activation of glial cells and elevated levels of pro-inflammatory cytokines such as IL-6 and TNF-α.
Chronic sleep loss is linked to an increased risk of cognitive decline and neurodegenerative conditions. Research indicates that sleep quality and duration can directly influence biological age markers, meaning that even modest sleep restriction over time can accelerate the ageing process at a cellular level.
Dr Gruffaz is emphatic that society has mischaracterised insufficient sleep. “Most people frame sleep loss as a productivity issue. It is actually a cellular ageing issue,” she said. When asked to rank interventions by biological significance, she places sleep protection at the top, followed by preserving muscle through weight-bearing exercise. “Maintain muscle mass through resistance training starting no later than your early 40s,” she advised.
Age-related muscle loss, known as sarcopenia, begins around age 30 and accelerates with time, leading to reduced strength, balance problems and a slower metabolism. Resistance training two to three times a week, targeting all major muscle groups, is one of the most effective ways to preserve muscle mass at any age, with experts recommending progressive overload for continued adaptation.
The NAD+ clock
The third priority Dr Gruffaz identifies concerns a molecule called NAD+ (nicotinamide adenine dinucleotide), which she describes as essential for both energy production and genetic repair within cells. “NAD+ is the central currency of cellular energy and DNA repair,” she noted.
NAD+ is a vital coenzyme present in all living cells, acting as a cofactor for enzymes such as sirtuins and PARPs involved in DNA repair, chromatin remodelling and metabolic regulation. Levels of NAD+ naturally decline with age, driven by decreased production and increased consumption by enzymes activated during DNA repair, inflammation and immune responses. Factors including alcohol consumption, overnutrition, UV exposure, viral infections and a sedentary lifestyle can further accelerate depletion.
“It drops by roughly 50 per cent between your 30s and your 50s,” Dr Gruffaz observed. Lower NAD+ levels are linked to impaired energy production, increased oxidative stress and a higher risk of age-related diseases including cognitive decline, metabolic disorders and frailty. Because NAD+ is critical for DNA repair, its decline diminishes the body’s ability to fix genetic damage, potentially leading to genomic instability and mutations.
Addressing its decline proactively, Dr Gruffaz argues, represents one of the most effective strategies available. She is clear that her recommendations should not be dismissed as mere lifestyle adjustments. “These are not lifestyle tweaks. They are direct interventions on the mechanisms that determine how fast your cells age,” she stated.
For those who have spent decades believing that ageing is a distant concern, her message is stark: the biological processes that determine how we age are already well underway.