A reliable biomarker for biological age would be some measure that reflects the level of cell and tissue damage present in an individual. The existence of such a biomarker would greatly speed up work on treatments for aging, allowing at least preliminary evaluation of the effectiveness of potential rejuvenation therapies based on damage repair very soon after their application in a test subject. The only presently available option is to run life span studies, to take the wait and see approach, which is very expensive and time-consuming, even in mice.
Researchers have made inroads towards a biomarker for aging by looking at DNA methylation patterns, and here is news of an analogous project that analyzes changes in gene expression levels. By the sound of it this new methodology only captures a slice of the wide-ranging cellular responses to accumulating damage, missing some of the important changes related to, for example, deterioration of the cardiovascular system:
Researchers used a process called RNA-profiling to measure and compare gene expression in thousands of human tissue samples. Rather than looking for genes associated with disease or extreme longevity, the researchers discovered that the "activation" of 150 genes in the blood, brain and muscle tissue were a hallmark of good health at 65 years of age. The researchers were then able to create a reproducible formula for "healthy ageing," and use this to tell how well a person is ageing when compared to others born the same year.
The researchers found an extensive range in "biological age" scores of people born at the same time indicating that a person's biological age is separate and distinct to his or her chronological age. Importantly, a low score was found to correlate with cognitive decline, implying that the molecular test could translate into a simple blood test to predict those most at risk of Alzheimer's disease or other dementias and suitable for taking part in prevention trials. A person's score was not, however, found to correlate with common lifestyle-associated conditions, such as heart disease and diabetes, and is therefore likely to represent a unique rate of ageing largely independent of a person's lifestyle choices.
However, the study does not provide insight into how to improve a person's score and thus alter their "biological age." While a low score could be considered as "accelerated ageing," an important aspect of the work suggests that ageing does not now need to be defined only by the appearance of disease. "Given the biological complexity of the ageing process, until now there has been no reliable way to measure how well a person is ageing compared with their peers. Physical capacity such as strength or onset of disease is often used to assess healthy ageing in the elderly but in contrast, we can now measure ageing before symptoms of decline or illness occur. We now need to find out more about why these vast differences in ageing occur, with the hope that the test could be used to reduce the risk of developing diseases associated with age."