Midlife Behavior Predicts Lifespan in Animals and Humans

A new study from Stanford University has found that subtle differences in an animal’s behavior by midlife can predict how long We see likely to live, including in humans. The research, which closely monitored African turquoise killifish throughout their lives, revealed that movement and sleep patterns in midlife serve as early indicators of lifespan.

By tracking 81 individual fish under constant camera surveillance and collecting billions of video frames, researchers were able to extract detailed measures of posture, speed, movement, and rest. Despite the fish sharing similar genetics and living in identical conditions, they aged in very different ways, with these differences becoming apparent by midlife.

Fish that stayed active and slept mostly at night tended to live longer, while those slowing down earlier lived shorter lives.

Stanford University

The study found that aging did not unfold smoothly but occurred in sudden jumps between stages. By closely monitoring the same individuals continuously across their adult lives, researchers were able to observe the personal timeline of aging — including twists, plateaus, and moments when things suddenly change — something traditional studies comparing young and old animals often miss.

By the time animals reach midlife, their everyday habits can offer clues about how long they are likely to live.

Stanford University

The research suggests that tracking daily habits such as movement and sleep — now commonly recorded by wearable devices in humans — could provide early clues about how aging progresses in people. The scientists believe behavior may be one of the earliest and most sensitive readouts of how aging is unfolding, not just in fish but in all vertebrate animals.

The study was led by postdoctoral scholars Claire Bedbrook and Ravi Nath and grew out of a collaboration between the labs of geneticist Anne Brunet and bioengineer Karl Deisseroth at Stanford. It was supported by the Knight Initiative for Brain Resilience at Stanford’s Wu Tsai Neurosciences Institute and published in Science on March 12, 2026.

Although the research focused on fish, the findings have implications for understanding human aging. The African turquoise killifish, which lives only about four to eight months, shares many biological features with longer-lived vertebrates, making it a valuable model for aging studies. By observing how behavior changes over the lifespan in a controlled environment, researchers aim to uncover patterns that may apply across species.