Many commercial tests that assess biological age take genetic data from saliva samples or oral swabs. Nevertheless, a recent study indicates that blood samples are usually required for precise results.
Individuals may exhibit a biological age that is either older or younger than their chronological age, influenced largely by the stressors they encounter. While scientists can gauge biological age, the type of tissue used for measurement plays a crucial role according to a new research study conducted by Penn State’s Department of Biobehavioral Health.
Your biological age refers to how well your body is performing, which is distinct from chronological age, the total duration since your birth. Although chronological age often correlates with disease likelihood, biological age allows researchers and healthcare professionals to gain a more nuanced view of an individual’s risk for various diseases, such as cancers and dementia, as it can be influenced by lifestyle and environmental factors.
To accurately assess biological age, the correct tissue type is essential, as highlighted by a study led by Abner Apsley, a doctoral student in the Penn State Molecular, Cellular, and Integrative Biosciences Graduate Program, and his supervisor, Idan Shalev, associate professor of biobehavioral health at Penn State. Their findings were published in Aging Cell.
In recent times, researchers have developed numerous epigenetic clocks—tools that compare a person’s biological age to their chronological age. With the rise in popularity of these clocks, many companies have begun to offer services that evaluate biological age based on customer tissue samples compared to established epigenetic clocks.
Researchers build these clocks by gathering tissue samples from a large group of individuals and analyzing differences in epigenetic markers—indicators of DNA methylation—over a person’s lifetime. Using machine learning, they identify which markers correlate with chronological age, allowing them to assess if an individual’s epigenetic profile aligns with their chronological age.
Understanding one’s biological age could provide insights into necessary lifestyle changes to promote longevity. However, the researchers note that validated clinical applications of epigenetic clocks are not yet common.
“Aging drives many common illnesses, including dementia, cardiovascular disease, and cancer,” said Shalev. “While biological age measurements are not diagnoses of health conditions, they can indicate an individual’s risk for age-related diseases.”
Some private companies offer biological age assessments by having clients submit saliva samples in test tubes. These samples are then analyzed for epigenetic data, and the companies use existing epigenetic clocks to estimate the client’s biological age. However, as noted by the researchers, most of these clocks are derived from blood samples rather than saliva, prompting the desire to compare different tissue types in this study.
The research team evaluated five tissue types against seven epigenetic clocks using 284 tissue samples from 83 participants aged between 9 and 70. They discovered that, in six out of the seven clocks examined, oral tissue produced significantly less accurate biological age estimations compared to blood samples.
“We assessed three blood sample types along with two oral tissues—saliva and cheek swabs,” said Apsley, the lead researcher. “For nearly all epigenetic clocks analyzed, oral tissue yielded considerably higher biological age estimates for subjects. In some instances, these estimates were up to 30 years older than expected; such inaccuracy is alarming. It is evident that the tissue used to determine someone’s biological age must correspond to the tissue type utilized when the epigenetic clock was developed. Otherwise, the biological age estimates will be invalid.”
The study results revealed that blood tissue samples produced consistent biological age estimates across various epigenetic clocks. In contrast, oral tissue samples consistently showed higher biological ages across the clocks, except for one epigenetic clock that was developed using both blood and cheek swab samples, which provided more reliable age estimates for different tissues.
“Most established clocks have been formulated using blood samples,” Apsley noted. “These findings highlight an essential lesson for this emerging field. If medical professionals or companies wish to use saliva or cheek swabs for biological age assessments, they must create specific epigenetic clocks based on those tissues. Currently, blood is necessary for accurate biological age assessment in most situations.”
While biological age tests are not yet prevalent in clinical settings, the researchers indicated that it could eventually help identify patients who may need interventions to slow the onset of age-related diseases due to their increased biological age. Conversely, individuals with a younger biological age might be more suitable candidates for surgery compared to those of the same chronological age. There are also various potential applications for biological age estimations.
“Researchers are continuously exploring how to utilize biological age,” Shalev explained, noting that their focus lies primarily in medical applications. “However, epigenetic clocks have also been employed with blood samples gathered from crime scenes to assist forensic scientists in estimating the ages of suspects. The future of this field is still unknown.”
Additional contributors to the study include Qiaofeng Ye, Christopher Chiaro, John Kozlosky, and Hannah Schreier from the Penn State Department of Biobehavioral Health; Avshalom Caspi, Laura Etzel-House, and Karen Sugden of Duke University; Waylon Hastings from Texas A&M University; Christine Heim from the Berlin Institute of Health at Charite; and Jennie Noll and Chad Shenk from the University of Rochester.
This research was funded by the National Institute on Aging, the National Institute of Environmental Health Sciences, the National Institute of Child Health and Human Development, the National Center for Advancing Translational Sciences, and the Penn State College of Medicine.
