One anti-ageing therapy is never enough
Drugs that clear out aged cells work well in mice, but extend their lives less than calorie restriction does. Why? Because ageing has no single cause. And that has major implications for how we should evaluate longevity therapies.
Biological ageing results from multiple simultaneous processes that partly reinforce one another. Senescent cells (cells that stop dividing but do not die), protein aggregation, DNA damage, mitochondrial decline: each mechanism contributes. The authors argue that treating just one cause has little effect on overall healthspan as long as the others remain unaddressed.
As an example, they point to amyloid-beta clearance in Alzheimer’s disease. Removing those protein accumulations is in principle beneficial, but does little for patients in later stages of the disease, because other mechanisms have by then become dominant. Solving one problem changes nothing about the rest.
The problem with lifespan as a metric
The piece also argues for separating healthspan (the period of healthy functioning) from lifespan as a measure of progress. A therapy may be excellent at addressing one specific cause of ageing while showing little visible effect on overall healthspan or lifespan. That does not mean the therapy fails. It only means the other causes have not been treated either.
This is a relevant insight for interpreting longevity studies. If a new compound shows no statistically significant effect on lifespan, that does not automatically mean it is useless. It may be a necessary component of a broader combination approach.
What does work?
The authors advocate for more research into combination therapies that address multiple ageing causes simultaneously. They also propose evaluating individual therapies on how well they achieve their specific target, rather than on the end result of lifespan. That requires different endpoints: biomarkers measuring distinct forms of cellular and tissue damage.
This is an opinion piece, not a primary study. The reasoning draws on existing literature and is qualitative in nature. Nonetheless, it offers a clear conceptual framework that helps explain why longevity research advances so slowly, despite its many promising individual findings.
Search terms to explore further: multifactorial ageing model combination therapy | senolytic healthspan efficacy | rejuvenation biotechnology biomarkers