A fluorescence microscope. Editorial illustration.
Telomere length is sometimes presented as a way to put a number on biological age. A study of 84 adults around age 51 illustrates why that number is hard to interpret. Shorter telomeres tracked with older age and, in one statistical model, with higher perceived stress. Aerobic fitness, muscle performance and lifestyle measures showed no consistent independent relationships in this group.
Evidence level Human Observational Research. This was a cross-sectional study of 84 adults and measured telomeres in blood cells.
Why telomeres interest aging researchers
Telomeres are repeating stretches of DNA and associated proteins that protect chromosome ends. In many cells they shorten as cells divide. When some telomeres become critically short, they can trigger a damage response that stops a cell from dividing. That makes telomeres relevant to cellular aging. A blood-cell measurement, however, samples one part of the body and varies with the mix and history of the cells in the sample.
What the study measured
The team measured telomeres in white blood cells using high-throughput quantitative fluorescence in situ hybridization. In this method, a fluorescent probe binds to telomere DNA, and imaging software converts the strength of that signal into an estimate of length. The researchers examined the median and the 20th percentile of telomere length to capture a typical measurement and the shorter end of the distribution.
Participants completed a 10-item questionnaire about perceived stress over the previous month. The study also assessed body composition, aerobic fitness, neuromuscular performance, blood markers and behaviours such as physical activity, smoking and alcohol use.
What held up in the statistical models
In a model that included age, sex, perceived stress and chronic disease status, higher stress scores were associated with shorter median and short-end telomere lengths. The authors also reported an association with chronic disease. The disease coding shown in the table appears inconsistent with the direction described in the text, so the direction needs clarification. The broader set of exploratory comparisons did not survive correction for multiple testing.
The fitness, physical performance and lifestyle results offer little basis for general conclusions. A small sample drawn largely from middle-aged adults has limited power to detect modest relationships, especially when exposures vary little. A single stress questionnaire also cannot show how long a person experienced stress or whether it preceded any difference in telomere length.
Why a single measurement has limits
A one-time comparison cannot measure how fast anyone’s telomeres are shortening. It also cannot establish that stress caused the differences. Repeated measurements in larger groups would help distinguish a stable difference between people from a change within the same person. For individual biological age, a telomere result describes one feature of the sampled cells and needs more context to say anything about health or function.
Related reading on how telomeres connect aging and cancer.
Original research
Skurvydas A, Dadeliene R, Aukstikalnis T, et al. Midlife telomere length is associated with perceived stress and chronic disease rather than lifestyle or physical function. Scientific Reports, November 11, 2026.