Women with type 2 diabetes who started on metformin rather than a sulfonylurea had roughly 30 percent lower odds of dying before age 90, according to a new study built on decades of data from the Women’s Health Initiative. The finding adds a striking data point to a long-running debate over whether a cheap, widely prescribed diabetes drug might also slow aging itself, Yet the result comes from an observational design, not a randomized trial, and the question of whether metformin truly extends life or simply marks healthier patients remains open.
A 30 Percent Gap in Survival to Age 90
The study, published in The Journals of Gerontology: Series A, used a target-trial emulation framework to compare women who began metformin against those who began a sulfonylurea after developing type 2 diabetes during the WHI follow-up period. Researchers narrowed the comparison to 438 matched participants, balancing the two groups on health characteristics so the drug choice, rather than baseline fitness, would drive any observed difference. Among those matched pairs, metformin initiators showed approximately 30 percent lower risk of death before age 90, a threshold the authors define as “exceptional longevity.”
That effect size is large for an observational comparison of two first-line diabetes medications and is especially notable because earlier work had not focused specifically on women. The authors emphasize that few prior cohorts have followed women long enough, and with sufficient clinical detail, to evaluate survival into the ninth decade by initial diabetes therapy. By anchoring their outcome at age 90 and using modern causal-inference tools, the investigators aimed to move beyond short-term metabolic endpoints and toward a question that resonates with patients: which treatment is associated with living longer, not just with better lab numbers.
Why the Women’s Health Initiative Matters Here
The strength of this finding rests heavily on the data source. The Women’s Health Initiative, funded by the National Heart, Lung, and Blood Institute, enrolled postmenopausal women across the United States and tracked them for years across multiple health outcomes, including cardiovascular events, cancers, fractures, and mortality. That long duration of follow-up is exactly what longevity research demands, because survival differences between drug classes can take a decade or more to become visible. The WHI’s scale and federal funding give the dataset a level of rigor that smaller pharmacy-claims studies typically lack, and the UC San Diego research team framed the work explicitly within the emerging field of gerotherapeutics, the idea that certain drugs might target biological aging rather than a single disease.
The investigators also leaned on best practices for observational science. According to reporting from an earlier WHI methods paper, the study design and analysis were aligned with established standards such as the STROBE recommendations for cohort studies, which call for clear definitions of exposures, outcomes, and confounders. That transparency matters because target-trial emulation, while increasingly respected, still cannot fully replicate the certainty of a randomized controlled trial. Readers should understand that the 30 percent figure describes an association, not a proven cause-and-effect relationship, and that unmeasured differences between the metformin and sulfonylurea groups could still influence who reaches age 90.
Metformin’s Track Record: Strong but Incomplete
Metformin has carried a reputation as something more than a glucose-lowering pill for over two decades. The landmark UKPDS 34 trial, a large randomized study in newly diagnosed type 2 diabetes, showed that intensive blood-glucose control with metformin reduced diabetes-related complications and all-cause mortality in overweight adults compared with diet alone. Those results helped cement metformin as a first-line therapy worldwide and planted the seed for broader claims about the drug’s protective effects beyond blood sugar alone, including potential benefits on cardiovascular risk factors and inflammation that could, in theory, influence lifespan.
Yet the evidence for metformin as an anti-aging therapy remains incomplete. The new WHI analysis adds to a body of observational work suggesting that people with diabetes who take metformin may live longer than those on alternative agents, but it does not prove that starting metformin causes exceptional longevity. Researchers at institutions such as UC San Diego and their collaborators have highlighted the need for randomized trials that enroll older adults and track hard outcomes like disability, frailty, and survival, not just glucose control. Until such trials are completed, enthusiasm about metformin’s geroprotective potential has to be tempered by the recognition that healthier patients are often steered toward metformin, which can exaggerate apparent benefits in non-randomized data.
What This Means for Women and for Research
For the millions of women living with type 2 diabetes, the practical takeaway is cautious but encouraging. Metformin is already the most commonly prescribed first-line treatment, so many patients are already on the drug that showed the longevity association in the WHI cohort. The study does not suggest that women without diabetes should start taking metformin, nor does it override individualized treatment decisions that account for kidney function, gastrointestinal tolerance, and interactions with other medications. Instead, the results reinforce existing guidelines that favor metformin as an initial therapy when it is safe and tolerated, while underscoring that sulfonylureas may not be equivalent from a long-term survival standpoint in older women.
The new analysis also helps shape the research agenda. By demonstrating a sizable difference in survival to age 90 between treatment groups that were carefully matched on baseline characteristics, the investigators have provided a strong rationale for randomized trials focused on aging outcomes. Commentaries associated with the WHI work, including those cited in the journal’s online materials, argue that future studies should examine not just whether metformin users live longer, but whether they spend more of those years free of disability, dementia, and cardiovascular events. Such trials would need to enroll diverse populations of older adults, including those without diabetes, to determine whether any longevity signal is specific to glucose metabolism or reflects broader effects on aging biology.
Unanswered Questions and the Road Ahead
One underexplored angle in the current coverage is whether metformin’s longevity signal in postmenopausal women reflects something specific to female biology after menopause or simply the characteristics of the WHI cohort. Hormonal changes, shifts in body fat distribution, and differing patterns of cardiovascular risk could all modulate how a drug like metformin interacts with aging pathways, but the present study was not designed to tease apart those mechanisms. The authors adjusted for many clinical variables, yet they could not fully account for factors such as diet quality, physical activity over time, or subtle differences in healthcare access that might influence both drug choice and survival into very old age.
For now, the most defensible conclusion is that, among older women who developed type 2 diabetes during WHI follow-up, those who started metformin rather than a sulfonylurea were more likely to reach age 90, even after careful statistical balancing. Whether that pattern reflects a true geroprotective effect or a sophisticated form of confounding will only be answered by prospective trials that randomize participants to metformin or alternative strategies and follow them for many years. Until then, clinicians can view the WHI findings as an additional reason to favor metformin when appropriate, and patients can see them as a reminder that choices about diabetes treatment may echo far beyond blood sugar numbers, potentially influencing who lives long enough to join the ranks of the exceptionally old.
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*This article was researched with the help of AI, with human editors creating the final content.
