by Dr. Georgiana Ozana Tache

Physical Medicine and Rehabilitation Senior Physician, Lecturer at the “Carol Davila” University of Medicine and Pharmacy, Bucharest

Age Can No Longer Be Understood Simply as the Number of Years on an ID Card

In modern medicine, increasing attention is being given to the difference between chronological age and biological age — in other words, the difference between how old we are and how well our bodies actually function.

Chronological age is fixed; it represents the time elapsed since birth. Biological age, however, is far more dynamic. It reflects the actual condition of the body’s systems: cardiovascular, metabolic and digestive, immune, musculoskeletal, and neurocognitive. It can be influenced by genetics, lifestyle, environment, chronic diseases, sleep, nutrition, physical activity levels, and cumulative exposure to stress. In this sense, two people of the same chronological age may have profoundly different biological profiles.

Why This Topic Matters

Aging is not simply a passive accumulation of years, but a complex biological process associated with cellular and molecular changes: genomic instability, telomere shortening, epigenetic alterations, loss of proteostasis, chronic low-grade inflammation, mitochondrial dysfunction, cellular senescence, and impaired intercellular communication. The 2023 update of the “hallmarks of aging” concept expanded this perspective further, including chronic inflammation, dysbiosis, and macroautophagy among the key mechanisms involved in aging.

The practical relevance is clear: aging is the main risk factor for many chronic diseases, including cardiovascular, metabolic, neurodegenerative, oncological, and musculoskeletal disorders. Therefore, assessing biological age should not be viewed as a commercial “anti-aging” exercise, but rather as an attempt to identify vulnerabilities earlier and intervene before disease becomes clinically apparent.

The Importance of Biological Markers in Assessing Biological Age

Biological markers are measurable indicators of a biological, physiological, or pathological state. In aging assessment, these markers may be simple and already widely available in medical practice: blood pressure, waist circumference, body mass index, lipid profile, blood glucose, glycated hemoglobin, C-reactive protein, kidney function, liver enzymes, vitamin D, bone mineral density, grip strength, gait speed, or exercise capacity.

There are also more sophisticated biomarkers, such as epigenetic clocks based on DNA methylation. These estimate biological age by analysing chemical modifications in DNA that accumulate or remodel over time. The first multi-tissue epigenetic clock, described by Steve Horvath, used 353 DNA methylation markers to estimate biological age. Other models, such as PhenoAge, integrate clinical and laboratory biomarkers, including albumin, creatinine, glucose, C-reactive protein, mean corpuscular volume, alkaline phosphatase, and white blood cell count.

Still, the essential message remains this: there is no single test capable of perfectly defining biological age. In clinical practice, the most useful approach remains the integrated interpretation of clinical, functional, and biological markers.

Biological Age, Preventive Medicine, and Functional Health

The major advantage of the biological age concept is that it shifts attention away from already established disease and toward the risk trajectory itself. It allows for a more practical discussion about prevention, functional health, and what medicine increasingly refers to as “healthspan” — the period of life lived in good health, autonomy, and functionality.

However, the limitations must also be clearly acknowledged. Some commercial “biological age” tests may be highly attractive but still lack fully validated clinical utility. Epigenetic clocks are promising, but they should not be turned into absolute verdicts. They may guide research and personalised medicine, but they cannot replace clinical evaluation, patient history, physical examination, routine investigations, and medical interpretation.

Therefore, the most prudent formulation is this: biological age is a useful clinical and preventive concept, but not yet a single, standardised, and self-sufficient diagnosis.

Rehabilitation Medicine

For physical and rehabilitation medicine, this topic is particularly relevant. Our specialty lies precisely at the intersection of function, prevention, movement, autonomy, and quality of life. If biological age describes how well the body functions, rehabilitation medicine provides the tools through which this function can be assessed and optimised.

Physical exercise is one of the most solid non-pharmacological interventions impacting aging: it improves cardiorespiratory fitness, insulin sensitivity, metabolic profile, muscle strength, balance, bone density, sleep, mood, and cognitive function. The World Health Organization recommends that adults engage in 150–300 minutes per week of moderate aerobic physical activity or 75–150 minutes of vigorous activity, combined with muscle-strengthening exercises involving all major muscle groups at least twice per week.

In a modern approach, exercise is not merely “recommended movement,” but a medical prescription. It should be individualised according to the FITT-VP principle: frequency, intensity, time, type, volume, and progression. This same logic appears throughout all my previous materials and presentations, where physical exercise, nutrition, sleep, and stress management are presented as interventions capable of modifying biological and functional trajectories, especially in women during the menopausal transition and as we age.

Lifestyle as Preventive Medicine

Redefining biological age does not mean making the unrealistic promise that aging can be stopped. More accurately, it means recognising that we can influence the pace and clinical expression of aging. Sleep, nutrition, physical activity, maintaining muscle mass, weight control, smoking cessation, reducing sedentary behaviour, stress management, and maintaining social connections are all interventions with cumulative effects on health.

In practice, patients do not simply need to learn “what their biological age is.” They need a coherent plan: understanding their risks, what can be modified, what should be monitored, and how medical recommendations can be transformed into sustainable behaviour.

Future Perspectives

In the coming years, biological age assessment will likely become increasingly integrated with digital medicine, artificial intelligence, molecular biomarkers, wearable device data, and predictive risk models. These tools may help personalise prevention strategies, but their real value will depend on medical interpretation and the application of validated interventions.

For physical and rehabilitation medicine, this represents a major opportunity. Rehabilitation should not be understood solely as an intervention after disease or injury, but as a medicine of function, prevention, and active longevity.

Ultimately, redefining biological age means redefining the medical objective itself: not merely adding years to life, but adding function, autonomy, and quality to the years we live.