A friend of Maja Olecka, approaching her 40th birthday, suddenly found her tolerance for alcohol drastically reduced. Quantities she once handled with ease now left her incapacitated, accompanied by significantly worse hangovers. This experience is far from isolated; many individuals in their mid-life years report similar shifts, with some choosing to abstain from alcohol altogether.
Olecka, a researcher at the Leibniz Institute on Aging – Fritz Lipmann Institute in Jena, Germany, suggests a compelling explanation. She posits that this age bracket often witnesses a rapid acceleration in the ageing process, directly impacting the body’s capacity to metabolize alcohol. This phenomenon, however, extends beyond alcohol intolerance. This accelerated ageing, marked by dramatic molecular alterations, is also linked to a faster rate of muscle loss, skin degradation, quicker depletion of immune cells, and a notably higher risk of cardiovascular disease and mortality.
Further research indicates that these significant surges in ageing might recur, approximately around the ages of 60 and 80. This observation challenges the long-held notion of ageing as a slow, linear progression from youth into old age. “Many contemporary definitions of ageing are describing it as a gradual, linear process,” Olecka notes. “We have to abandon this assumption.”
Instead, the process may be more akin to navigating whitewater rapids: extended periods of calm are interspersed with sudden, intense phases of turbulence. These turbulent periods can cause significant damage, ultimately leading to a decline. While this surprising discovery remains in its nascent stages, it holds profound implications for our understanding of ageing and strategies aimed at slowing its progression.
Ageing: Not a Steady Slide, But a Series of Jumps
The initial indications that ageing occurs in distinct stages emerged from studies on fruit flies, specifically the species Drosophila melanogaster.
In 2011, Michael Rera, then affiliated with the French National Institute of Health and Medical Research in Paris, identified a unique phase that these flies enter toward the end of their lives. By feeding the flies blue dye, initially to gauge food consumption, Rera observed that older flies turned blue. This colouration occurred because their intestinal permeability increased with age, allowing the dye to seep into their body cavities. This “Smurf” state became a reliable indicator of impending death.
Flies transitioned into Smurfdom with remarkable speed: healthy one day, blue the next, and deceased shortly thereafter. The Smurf state was also characterized by classic signs of senescence, including reduced spontaneous motor activity and diminished energy reserves. Rera, now at the Jacques Monod Institute in Paris, proposed that the ageing process in Drosophila is biphasic, progressing slowly through most of the fly’s adult life before abruptly shifting to a significantly more decrepit condition. This suggests the flies can tolerate accumulated molecular damage for a considerable time, eventually reaching a threshold they can no longer withstand.
Since these initial findings, the Smurf state and its associated intestinal permeability have been observed in other organisms, such as nematode worms and zebrafish, suggesting gut permeability is a common feature of ageing. While humans do not turn blue as they age, accumulating evidence over recent years points to similar rapid escalations in the ageing process, potentially for analogous reasons.
Evidence of Ageing Surges in Humans
For instance, in 2022, a research team at the Wellcome Sanger Institute in Hinxton, UK, identified a significant and abrupt transition in the blood cell production capability around the age of 70. Before this age, most individuals maintain a robust and stable population of 20,000 to 200,000 hematopoietic stem cells responsible for generating new red and white blood cells and platelets. Post-70, this number drastically decreases, with only a few hundred or even tens of stem cells producing the majority of new blood cells. This sharp decline significantly elevates the risk of anemia, immune system dysfunction, impaired tissue regeneration, and blood cancers, all of which contribute to increased mortality and were already known to surge in individuals over 70.
The apparent cause of this abrupt decline is the cumulative molecular damage sustained by most hematopoietic stem cells over their lifespan. Steve Hoffmann, a colleague of Olecka at the Leibniz Institute on Aging, describes this as a classic ‘tipping point’ – a phenomenon where a system undergoes a sudden, often irreversible shift from one equilibrium state to another, following a prolonged period of pressure build-up. This concept is well-established in fields like physics, ecology, and climate science, and Olecka and Hoffmann are keen to introduce it carefully into ageing research.
“It’s a tricky term because there is no strict scientific definition of a tipping point and different fields use it in different ways,” Olecka explains. “But I think it is a very good term to convey the general concept of abrupt change after crossing some threshold.”
Our Ageing Tipping Points
Olecka and Hoffmann’s hypothesis is supported by a growing body of evidence suggesting that ageing processes in various body systems are amplified after critical biological limits are breached. Researchers have identified several such tipping points, many occurring around similar ages. For example, in the late 2010s, a team led by Tony Wyss-Coray at Stanford University investigated heterochronic parabiosis, a procedure connecting the circulatory systems of two animals. In a 2011 study, Wyss-Coray and colleagues linked an aged mouse with a young one, observing rejuvenation in the older mouse and ageing in the younger one. These findings indicated that blood, or more specifically its plasma component, contains key regulators of ageing.
To identify these regulators, Wyss-Coray’s team tracked changes in plasma proteins throughout human ageing. Their 2019 study, involving blood samples from 4,263 individuals aged 18 to 95, analyzed the levels of 2,925 proteins. Contrary to expectations of gradual, linear changes with age, they discovered participants clustered into four distinct groups: under 34, 34-60, 61-78, and over 78. Within each group, protein profiles were largely consistent, but at ages 34, 60, and 78, abrupt shifts occurred, with some protein levels dramatically increasing while others plummeted. Notably, some proteins enriched in older age groups were already associated with cardiovascular disease and Alzheimer’s. The researchers also observed an increase in a protein linked to Down’s syndrome, a condition known for accelerated ageing.
Their conclusion was that humans undergo three distinct pulses of accelerated ageing around the ages of 34, 60, and 78. In a more in-depth investigation, Michael Snyder’s team at Stanford University examined RNA, metabolites, lipids, inflammatory molecules, and plasma proteins in 108 individuals aged 25 to 75. They found that molecules known as ageing markers spiked significantly during two brief windows: in the early to mid-40s and again around age 60. Both spikes were associated with increased risk of cardiovascular disease, impaired lipid metabolism, reduced muscle stability, and diminished skin integrity. The first spike was linked to a decreased ability to metabolize caffeine and alcohol efficiently, which could explain the midlife hangover phenomenon. The second spike suggested precipitous declines in kidney and immune system function.
“What we discovered is that most things aren’t changing linearly,” Snyder stated. Only 6.6 percent of the thousands of molecules tracked showed linear changes with age; 81 percent changed non-linearly. The alignment of these spikes with Wyss-Coray’s identified tipping points at ages 34 and 60 suggests they are detecting the same biological signals. Snyder’s team could not ascertain a spike at age 78 due to the age range of their oldest participants (up to 75).
Evidence also suggests that individual organs and systems age in stages. For instance, molecular profiles of skin samples from women aged 21 to 76, analyzed in 2020, revealed that older skin exhibited more molecular ageing markers. However, the transition from young to old skin was characterized by tipping points around ages 30, 50, and 65, dividing skin ageing into four distinct phases. In the brain’s plasma proteome, tipping points have been identified at ages 57, 70, and 78, coinciding with increased biomarkers of ageing. Furthermore, key immune cells, including B-cells, T-cells, and natural killer cells, experience two periods of decline and ageing around ages 40 and 65, likely contributing to the weakening immune function characteristic of ageing.
These tipping points may also explain puzzling patterns in the incidence of age-related diseases and mortality. According to Snyder, the occurrence of certain age-related diseases demonstrates step-wise changes. The risk of cardiovascular disease, for example, increases from 16% to 40% at age 40, remaining relatively stable until age 59 before jumping to approximately 75% at age 60 and then to about 85% after age 80. Similarly, the incidence of neurodegenerative conditions like Parkinson’s and Alzheimer’s accelerates first more gradually around age 40, and then more rapidly around age 65.
Mortality data also reveals subtle non-linearities. The long-held assumption is that mortality rates rise smoothly and exponentially throughout adulthood, doubling approximately every eight years. However, Aleksei Golubev’s detailed analysis of data from France, Sweden, and Japan uncovered three periods where mortality rates subtly but discernibly accelerated: around ages 17, 38, and 60. While the first acceleration may be attributed to external factors like accidents, the latter two align with molecular tipping points, suggesting they could be partly due to accelerated ageing.
What Triggers a Tipping Point?
Synthesizing evidence from various ageing tipping points, and accounting for some variations such as skin ageing, it appears that after reaching maturity, human life is roughly divided into phases lasting approximately 20 years. “I think we need more data, but from what I see, the most important transitions in humans are around 40, around 60 and then around 80,” Olecka suggests. While these phases are intuitively recognized as young adulthood, early middle age, late middle age, and old age, research indicates they possess distinct biological characteristics.
The precipitating factor for these sudden shifts is likely the accumulation of molecular damage that eventually overwhelms the body’s capacity to cope. This mirrors the process observed in fruit flies. Natural repair systems can mitigate these molecular changes up to a certain point, after which they become saturated or exhausted, leading the system to adopt a new state. While speculative, potential buffers include DNA repair mechanisms, antioxidants, and molecular “chaperones” that ensure proper protein folding. Domino effects, where crossing one tipping point triggers others, are also possible.
Snyder hypothesizes that lifestyle changes partially contribute to the transition around age 40. “My guess is that people are not exercising as much, they become more sedentary and they’re probably not eating as well,” he says, “and it catches up with them when they hit their early 40s.” This suggests the possibility of delaying tipping points through diet, exercise, and potentially future pharmaceutical interventions termed “anti-transition agents.”
Although not all ageing processes are non-linear (mutation accumulation, for example, is linear), Hoffmann highlights the exceptional interest in these non-linear transitions for identifying new targets for anti-ageing therapeutics. “For now, people are looking for anti-ageing medication that would work for everyone, but maybe we should look for strategies to stop or delay the transitions,” Olecka proposes. “This may be a more successful and more targeted approach.” While such drugs are still distant, initial steps have been made with genetic interventions designed to postpone the Smurf state in fruit flies.
Olecka and Hoffmann envision translating this fundamental research into a system for stratifying ageing. Individuals could be categorized into different stages (potentially four, five, or even six), allowing for tailored treatments. “We think that the transitions may mark natural boundaries between stages of ageing and be useful for prevention,” Olecka notes. “Some interventions may be beneficial in a younger stage, but be detrimental in the older stage of age.” The specifics of these applications, however, await further discovery.
Once a Rubicon has been crossed and a new age stage entered, the question of whether a return to a previous state is possible remains. “This is a very, very important question to answer,” Olecka states. “We don’t know yet.”
Snyder is actively analyzing data from a larger cohort followed for 12 years, aiming to identify interventions that might delay tipping points. By tracking lifestyles, he hopes to understand how some individuals might push these changes into their 50s or later and determine the factors contributing to this delay. With accumulating compelling evidence and ongoing research, the field of ageing itself may be approaching its own tipping point.