Scientists Are Getting Better at Testing Whether Aging Can Be Slowed

The science of slowing aging is entering a more rigorous phase—not because researchers have found a proven “anti-aging” treatment, but because they are developing better ways to test whether an intervention changes the rate of biological decline.

A 2025 analysis of more than 19,000 adults in the United States and England found that people born in the same era can age at substantially different rates. Researchers combined blood biomarkers, physical measurements and functional tests to estimate each participant’s “pace of aging.” Faster rates were consistently associated with later illness, disability and mortality, suggesting that the speed of biological decline may be a meaningful target for prevention.

That finding matters because conventional clinical trials can take decades to determine whether a treatment extends life. Scientists working in geroscience—the study of the biological mechanisms that contribute to aging and age-related disease—are therefore turning to intermediate measurements, including molecular “aging clocks” and composite health scores.

One 2025 study introduced a method called DunedinPACNI, which estimates a person’s longitudinal pace of aging from a single brain MRI. Across data sets including the UK Biobank and Alzheimer’s Disease Neuroimaging Initiative, faster scores were linked with cognitive impairment, brain atrophy, frailty, chronic disease and mortality. The method is not a treatment, and it cannot yet prove that changing the score would change a person’s health. Its value is practical: it could give researchers another way to evaluate interventions before waiting years for disease outcomes.

Human trials are beginning to produce signals, but they remain limited and uneven. In a follow-up analysis of the three-year DO-HEALTH trial, involving 777 older adults, daily omega-3 supplementation was associated with slower changes on several DNA-methylation aging clocks. Vitamin D, omega-3 and a home exercise program also showed an additive effect on one measure. The analysis was not designed to prove longer life, and the researchers cautioned that biological clocks capture only some aspects of aging.

Another randomized trial, known as TALENTs, studied 121 adults ages 60 to 70 who received either a nucleotide supplement or placebo for 19 weeks. The supplement group had a greater reduction in one DNA-methylation measure of biological age. However, the trial did not find a significant change in leukocyte telomere length, another commonly discussed aging marker. The short duration and narrow set of outcomes make it premature to interpret the result as evidence that the supplement extends healthspan or lifespan.

Drug research is moving along a similar path. The PEARL trial tested intermittent, low-dose rapamycin in healthy adults for 48 weeks, focusing primarily on safety and health-related measures rather than survival. Rapamycin is of interest because it affects nutrient-sensing pathways involved in aging biology, but it is not approved as an anti-aging drug. Questions about dosing, long-term safety and which people might benefit remain unresolved.

Animal studies continue to generate more dramatic results. In mice, a 2025 Nature Aging study reported that trametinib, alone and in combination with rapamycin, improved healthspan and extended lifespan. Such findings can reveal biological pathways worth testing, but results in mice do not establish that the same treatment is safe or effective in humans.

The strongest conclusion from the current research is therefore methodological rather than commercial. Aging appears to be modifiable in some biological and behavioral dimensions, but no intervention has yet been shown to safely and reliably make healthy humans live substantially longer. Researchers still need validated measures that predict meaningful outcomes, larger and longer randomized trials, and evidence that changes in molecular clocks translate into fewer diseases, preserved function and better quality of life.

For now, the field’s central goal is not to promise immortality. It is to delay the cluster of conditions that often arrive together in later life—and to prove, with clinical evidence, which strategies can do that.