Gauging biological age to predict future health

Age and health are clearly connected, with the risk for many
diseases and health conditions rising with age. Yet people of the same
age can show vast differences in overall health. Some have multiple
chronic conditions affecting various parts of the body by midlife, while
others have a clean bill of health into their 70s and beyond. One
theory holds that such differences stem from variation in biological
aging. This is the extent of damage that builds up across tissues and
organs, leading to chronic conditions, physical decline, and disability.

Existing measures of biological age, such as the Frailty Index, try
to capture a person’s health based on the number of health deficits they
have. But these approaches don’t fully capture the complexity of
biological aging. A research team led by Drs. Shabnam Salimi and Daniel
Raftery at the University of Washington School of Medicine and Drs.
Luigi Ferrucci and Marcel Salive at NIH’s National Institute on Aging
wanted to develop a way to better capture a person’s health and rate of
biological aging. The method they developed, called the Health Octo
Tool, is described in Nature Communications on May 5, 2025.

To develop the tool, the team turned to data from multiple long-term
studies that included more than 40,000 people. First, the
researchers defined disease states and their severity for each of 13
major organ systems based on accepted medical criteria. These systems
included cardiovascular, kidney, metabolic, gastrointestinal and liver,
respiratory, thyroid, blood, oral health, bones and muscles, sensory,
and the central nervous system. The team also considered whether a
person had a history of stroke or cancer.

The analysis of organ-specific disease was used to predict what the
researchers call Bodily Organ-Specific Clocks. Then, by combining all
the organ systems together, they created a measure, called the Body
Clock, that captures a person’s overall health state without regard to
chronological age.

The team found that the Body Clock accurately predicted a person’s
performance on a short assessment used to gauge physical functioning
including balance, walking speed, and strength. It also predicted
disability and mortality with more than 90% accuracy. The Body Clock
predicted health outcomes better than the Frailty Index.

The scientists went on to develop a collection of eight metrics that
reflect different aspects of a person’s health and biological age. For
example, they used the Bodily Organ-Specific Clocks and Body Clock to
calculate a person’s overall biological body age. Two other measures
consider how the Body Clock affects a person’s walking speed and their
physical and cognitive disability. 

Because these measures included early or pre-disease states, the
Health Octo Tool could be used to track changing health and disease
across a person’s lifespan. It may also identify those at risk for
accelerated aging. The hope is that it will contribute to development of
more effective lifestyle and healthcare strategies. Its use could
suggest personalized interventions by identifying health declines early.

“An aging-based framework offers a new path to discover biomarkers
and therapeutics that target organ-specific or whole-body aging, rather
than individual diseases,” Salimi says.

—by Kendall K. Morgan, Ph.D.