As the longevity industry exponentially grows, so does awareness of its fundamental concepts. By now, most enthusiasts are certainly aware of the distinction between chronological age — the number of times Earth has revolved around the sun since your birth — and biological age, the intricate measure of how old your body truly is.
Yet, amidst this discussion, another fascinating dimension emerges: subjective age. This nuanced and often overlooked metric potentially holds new keys in the pursuit of a longer, healthier life.
What Is Subjective Age?
Subjective age, sometimes also called psychological age, refers to how individuals perceive their own age. Imagine subjective age as the “feel” of your age — how old or young you sense yourself to be beyond the number of years you’ve lived.
The earliest studies on the discrepancies between chronological and subjective age go back to the 1980s [1]. However, this vibrant area of research is now gaining unprecedented momentum due to several factors [2]. Longitudinal data has been revealed, examining how subjective age influences health outcomes. Plus, the potential impact of subjective age on health has prompted interdisciplinary collaboration between behavioral sciences, social sciences, and health sciences.
These studies contribute a crucial clue to the complexities of aging, suggesting that aging isn’t solely a universal, biologically programmed process of wear and tear. Rather, it additionally relies on individual and societal perceptions.
Fluctuations in Subjective Age Across Our Lifespan
Subjective age is an ever-evolving journey that intertwines with the ebb and flow of life’s chapters. Early in life, our age aligns with our developmental stage. However, as adolescence sets in with its unmistakable egocentrism that most of us have been through, we start feeling older than our actual years [3]. Enter: midlife. That’s when an intriguing shift occurs where individuals often report feeling around 20% younger than their chronological age [4].
In his brilliant book “Age” [5], Professor Suresh Rattan, the founding father of the science of biological aging, offers an interesting explanation for that midlife phenomenon. He posits that by the age of 45, most humans achieve essential lifespan — the time required to fulfill the Darwinian purpose of life, which is successful reproduction for the continuation of generations. This could influence our subjective age, making individuals feel that they are “essentially” 45 years old, regardless of their chronological age. In most cases, even having a serious disease does not make them feel the actual weight of their years.
So seemingly, as Rattan eloquently puts it, “When the aging of the body starts, the aging of the mind stops.”
What Shapes Our Self-Perception of Age?
Subjective age is far from a fixed metric. It’s influenced by a myriad of factors and varies significantly across individuals and age brackets.
Understandably, high self-rated health and positive behavioral traits like extraversion, openness to experiences, and overall self-efficacy correlate with younger subjective age [6]. This paints an elaborate picture of a mind-body connection impacting how we feel about our age.
But, the role of cultural influences in this interplay also can’t be overstated. A study involving participants aged 30–95 years from China, Germany, and the US highlighted profound cultural disparities [7]. Chinese perceptions of aging, both in general and concerning oneself, were notably more pessimistic, correlating with older subjective age in certain life domains.
Yes, life domains. It turns out that even the context in which we find ourselves holds sway over our subjective age. That is evident in another study which has found that day-to-day settings, such as work, health, or financial environments, impact how old or young we feel [8]. In settings marked by prevalent negative age stereotypes, individuals tend to report lower subjective ages, indicating a conscious effort to distance themselves from the negativity typically associated with their age group.
All these different pieces make up the puzzle of our subjective age, revealing how dynamic our accounts of aging are.
Correlations Between Subjective Age and Biological Age
While previously we delved into why most older adults often feel younger than their chronological age, it’s not unheard of for some to experience a subjective age that exceeds their chronological one. Unfortunately for these individuals, recent research has shown that they also tend to be biologically older [9]. That is, their bodies are undergoing accelerated aging, possibly due to their perceived health and inflammatory profiles.
On a molecular level, researchers have investigated this relationship by examining telomere length. Telomeres are protective caps at the end of chromosomes that maintain chromosomal stability during cell division. As we age, telomeres shorten, and this attrition is a recognized hallmark of aging.
In a fascinating study, researchers measured telomere length in ex-prisoners of war who reported older subjective age [10]. The study revealed a concurrent shortening of telomeres. This suggests a link between feeling older and cellular aging, known as cellular senescence, another hallmark of aging.
Subjective Age’s Impact on Health Outcomes
As we’ve begun uncovering the links between our perceptions of aging and the actual progress of aging inside our bodies, it’s time to dig deeper into the data to see how this interplay translates into health outcomes and correlations with age-related diseases.
Subjective Age and Cardiovascular and Metabolic Health:
Research has shown that feeling younger than one’s calendar age is linked to better cardiovascular and metabolic health. Such individuals suffered significantly less from hypertension and diabetes [11]. Conversely, older subjective age was found to correlate with higher BMI and increased waist circumference, demonstrating a 10–20% higher likelihood of obesity-related measures for those who feel older than their age [12].
Subjective Age and Systemic Inflammation:
Examining the association between subjective age and C-reactive protein (CRP), regression analyses showed that individuals perceiving themselves as younger experienced lower CRP levels, suggesting lower systemic inflammation and possibly addressing the risks of immune dysfunction and related health concerns in older adults [13].
Subjective Age and Frailty Risk:
In a nationally representative study involving community-dwelling older adults, researchers found that subjective age independently predicted frailty risk [14]. Even after considering demographic and health-related factors, individuals who felt older than their actual age exhibited a higher likelihood of pre-frailty or frailty, underlining the potential impact of subjective age on physical vulnerability in older populations.
Subjective Age and Mental Health:
Research indicates a marked relationship between subjective age and mental health outcomes. Perceiving oneself as younger than actual age correlated positively with mental health, reducing the risk of major depressive episodes and promoting flourishing mental health [15]. On the other hand, in a longitudinal study, an older perceived age predicted higher future depressive symptoms [16].
Subjective Age and Brain Health:
Using MRI brain scans, researchers discovered intriguing links between subjective age and brain health in older individuals. Participants who felt younger than their actual age displayed fewer signs of brain aging, suggesting potentially better cognitive health [17]. Notably, those perceiving themselves as younger exhibited increased gray matter volume in key brain regions and scored higher on memory tests.
Subjective Age and Mortality Risk
Amidst the array of health outcomes tied to subjective age, let’s uncover how these diverse influences may shape mortality risk and longevity in older individuals.
Research so far spells good news for those of us who care for being young at heart. In a longitudinal study following subjects over 8 years, all-cause mortality rates were the lowest for participants who felt younger than their chronological age at 14.3% compared to 24.6% for those who felt older [18].
This revelation highlights a thrilling theory: perception wields a substantial influence on our longevity. Merely feeling younger, irrespective of interventions, inherently holds the potential to extend our years on this planet.
Strategies for Longevity and Subjective Age
Fortunately, current research presents a positive shift toward younger subjective age and a decrease in the rate of subjective age increase over time [19].
But is that enough?
If our intrinsic sense of age already holds such power over our health, then what if we harness this power to develop cutting-edge longevity interventions?
Count us in!
The authors of one of the most comprehensive literature reviews on the topic of subjective age concluded their paper by saying “We suggest that psychological affirmations could be used as an intervention to modify longevity and health expectations by 10 years.” [20]
This vision signifies a unique and promising avenue for exploration, albeit with significant work ahead. Developing psychological biomarkers of aging stands as a crucial step.
Plus, such ambitious biomedical research projects require the engagement of not only creative scientists but also dedicated health enthusiasts acting as sources of high-quality health data.
Enter: Rejuve.AI!
Rejuve.AI is a first-of-its-kind research network fostering decentralized collaboration among researchers, clinics, and health enthusiasts, all united in the battle against aging.
By leveraging groundbreaking AI and blockchain technologies, our network bypasses the inefficiencies of traditional research settings. We enable scientists to explore unconventional areas of research with untapped potential like subjective age. Such initiatives aim to expedite the discovery of novel longevity interventions and bring us all closer to our ancient ambition of living healthier for longer.
References:
[1] Montepare, J. M., & Lachman, M. E. (1989). “You’re only as old as you feel”: self-perceptions of age, fears of aging, and life satisfaction from adolescence to old age. Psychology and Aging, 4(1), 73–78. https://doi.org/10.1037//0882-7974.4.1.73
[2] Gerben Johan Westerhof, Nehrkorn-Bailey, A., Tseng, H.-Y., Brothers, A., Siebert, J., Wurm, S., Wahl, H., & Diehl, M. (2023). Longitudinal effects of subjective aging on health and longevity: An updated meta-analysis. Psychology and Aging, 38(3), 147–166. https://doi.org/10.1037/pag0000737
[3] Galambos, N. L., Turner, P. K., & Tilton-Weaver, L. C. (2005). Chronological and Subjective Age in Emerging Adulthood. Journal of Adolescent Research, 20(5), 538–556. https://doi.org/10.1177/0743558405274876
[4] Rubin, D. C., & Berntsen, D. (2006). People over forty feel 20% younger than their age: Subjective age across the lifespan. Psychonomic Bulletin & Review, 13(5), 776–780. https://doi.org/10.3758/bf03193996
[5] Rattan, S. (2019). Age. (p. 45). Aarhus University Press.
[6] Takatori, K., Matsumoto, D., Miyazaki, M., Yamasaki, N., & Moon, J.-S. (2019). The difference between self-perceived and chronological age in the elderly may correlate with general health, personality and the practice of good health behavior: A cross-sectional study. Archives of Gerontology and Geriatrics, 83, 13–19. https://doi.org/10.1016/j.archger.2019.03.009
[7] O’Brien, E. L., Hess, T. M., Kornadt, A. E., Rothermund, K., Fung, H., & Voss, P. (2017). Context Influences on the Subjective Experience of Aging: The Impact of Culture and Domains of Functioning. The Gerontologist, 57(suppl_2), S127–S137. https://doi.org/10.1093/geront/gnx015
[8] Kornadt, A. E., Hess, T. M., Voss, P., & Rothermund, K. (2016). Subjective Age Across the Life Span: A Differentiated, Longitudinal Approach. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences, gbw072. https://doi.org/10.1093/geronb/gbw072
[9] Stephan, Y., Sutin, A. R., Luchetti, M., & Terracciano, A. (2021). An older subjective age is related to accelerated epigenetic aging. Psychology and Aging. https://doi.org/10.1037/pag0000607
[10] Lahav, Y., Avidor, S., Stein, J. Y., Zhou, X., & Solomon, Z. (2018). Telomere Length and Depression Among Ex-Prisoners of War: The Role of Subjective Age. The Journals of Gerontology: Series B, 75(1), 21–29. https://doi.org/10.1093/geronb/gby006
[11] DEMAKAKOS, P., GJONCA, E., & NAZROO, J. (2007). Age Identity, Age Perceptions, and Health: Evidence from the English Longitudinal Study of Ageing. Annals of the New York Academy of Sciences, 1114(1), 279–287. https://doi.org/10.1196/annals.1396.021
[12] Stephan, Y., Sutin, A. R., & Terracciano, A. (2018). Subjective age and adiposity: evidence from five samples. International Journal of Obesity, 43(4), 938–941. https://doi.org/10.1038/s41366-018-0179-x
[13] Stephan, Y., Sutin, A. R., & Terracciano, A. (2015). Younger subjective age is associated with lower C-reactive protein among older adults. Brain, Behavior, and Immunity, 43, 33–36. https://doi.org/10.1016/j.bbi.2014.07.019
[14] Li, Y., Liu, M., Miyawaki, C. E., Sun, X., Hou, T., Tang, S., & Szanton, S. L. (2021). Bidirectional relationship between subjective age and frailty: a prospective cohort study. BMC Geriatrics, 21(1). https://doi.org/10.1186/s12877-021-02344-1
[15] Keyes, C. L. M., & Westerhof, G. J. (2012). Chronological and subjective age differences in flourishing mental health and major depressive episode. Aging & Mental Health, 16(1), 67–74. https://doi.org/10.1080/13607863.2011.596811
[16] Keyes, C. L. M., & Westerhof, G. J. (2012). Chronological and subjective age differences in flourishing mental health and major depressive episode. Aging & Mental Health, 16(1), 67–74. https://doi.org/10.1080/13607863.2011.596811
[17] Kwak, S., Kim, H., Chey, J., & Youm, Y. (2018). Feeling How Old I Am: Subjective Age Is Associated With Estimated Brain Age. Frontiers in Aging Neuroscience, 10. https://doi.org/10.3389/fnagi.2018.00168
[18] Rippon, I., & Steptoe, A. (2015). Feeling Old vs Being Old. JAMA Internal Medicine, 175(2), 307. https://doi.org/10.1001/jamainternmed.2014.6580
[19] Wettstein, M., Wahl, H.-W., Drewelies, J., Wurm, S., Huxhold, O., Ram, N., & Gerstorf, D. (2023). Younger Than Ever? Subjective Age Is Becoming Younger and Remains More Stable in Middle-Age and Older Adults Today. 095679762311645–095679762311645. https://doi.org/10.1177/09567976231164553
[20] Mitina, M., Young, S., & Zhavoronkov, A. (2020). Psychological aging, depression, and well-being. Aging, 12(18). https://doi.org/10.18632/aging.103880