Scientists Say Your Organs Don’t Grow Old Slowly—They Age in Two Sudden Bursts. Here’s When.

3 min readHere’s what you’ll learn when you read this story:The human body doesn’t age steadily—instead, organs largely experience two phases of rapid aging, also known as biphasic aging. A new study found that while some tissues, such as vascular, uterine, or vaginal tissue, don’t follow this two-phased aging, most do. Scientists reached this conclusion by developing a deep-learning model called Pathology-based Structural Aging Rate (PathStAR) to extract underlying tissue structure from 25,000 organ images in a public database and then plot molecular changes over time.Time is an incredibly complex concept that we tend to define in simple terms. Time marches inexorably forward—second by second, day by day, decade by decade—but if you plug Albert Einstein’s Special Theory of Relativity into this conceptualization, things suddenly aren’t so simple. In some ways, the same can be said for aging. Every year we add more candles to the birthday cake, but like time, this steady progression of aging is just a conception, not physical reality.In recent years, a growing body of research suggests that aging largely occurs in a “biphasic” pattern, meaning it ramps up during two specific periods in our lifetime. Now a new study in the journal Nature Aging is adding its own boulder to this growing mountain of evidence. Led by researchers at Sanford Burnham Prebys Medical Discovery Institute in San Diego and the National Institutes of Health (NIH), the study leverages artificial intelligence to pore over 25,000 organ images and create a map of how aging progresses in the body. The researchers found that while different organs age on different schedules, many tissues experience accelerated aging in a person’s 30s and 50s.“Our goal is to understand how aging occurs at a structural level,” Sanford Burnham Prebys’ Sanju Sinha, PhD, senior author of the study, said in a press statement. “To do this, we needed thousands of normal organ tissues over a wide range of ages.”The team relied on data in the Genotype-Tissue Expression Project, a large archive of tissue- and cell-specific gene expression and regulation created by the NIH to understand how inherent genetic differences are expressed throughout the human body. Within this data, researchers found 25,000 images of biopsies of 40 different tissues from roughly 1,000 deceased donors between the ages of 21 and 70. They then developed an AI model, named the Pathology-based Structural Aging Rate (PathStAR), to essentially extract underlying tissue structure and then chart molecular changes over time.“This showed that the structural information embedded in the clinical images could be measured and deliver an answer that lines up with what we know about the functional aging of a tissue,” Sinha said in a press statement. “And we learned that the structural changes in tissue with aging are so apparent that the model does not even need any training on chronological age to track them.”As a proof of concept, the researchers conducted their first investigation using this model on the ovaries. Examining 250 scanned histopathology slides from ovarian tissue, they discovered that the ovaries experience accelerated aging at ages 35 to 40 and ages 55 to 60. Looking at the rest of the data, the scientists were able to narrow in on 15 other types of tissue. The vascular system, for example, only experiences rapid aging from ages 30 until 39, while other tissues, such as the uterus and vagina, quickly age around the early 50s. However, the majority of these tissues did age in two phases, and each showed the same underlying rise in inflammation-related genes.These findings are largely in line with research from August 2024 in which researchers from Stanford University examined thousands of molecules in the skin of humans aged 25 to 75 and found a similar trace of biphasic aging. They concluded that rapid aging occurs around the mid-40s and early 60s. It’s been recently noted, however, that some of the molecular detection methods in that article are in question.The goal of this new study is to develop a kind of “structural aging atlas” that can help scientists develop anti-aging treatments. While we don’t have technology to stop aging in its tracks, if we can understand how the complicated flow of time actually changes our bodies, maybe we can at least live healthier lives as the years go by.Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.