US scientists have examined the biological processes behind five widely used ageing tests, finding that different methods appear to capture different aspects of how the human body ages.

Researchers analysed blood samples from 3,227 people who took part in the US Health and Retirement Study. They compared five commonly used epigenetic clocks with patterns of gene activity in the participants’ blood to determine what biological changes were associated with faster ageing according to each test.

Epigenetic clocks are mathematical tools that estimate biological age using DNA methylation, chemical changes that can influence how genes function without altering the underlying genetic code.

Scientists have increasingly used these clocks to investigate links between biological ageing, disease, physical decline and the risk of death. However, researchers have not always known precisely what processes inside the body were being reflected when a clock indicated that someone was ageing faster than expected.

The new study found that the five clocks were associated with different molecular signs of ageing. Some were more strongly connected to processes involved in energy use and cell growth, while others showed stronger links to immune activity and inflammation.

Despite those differences, the clocks shared several biological features. These included changes involving the immune system, metabolism and communication between cells.

The findings could help researchers select the most appropriate biological ageing test for a particular study. A clock associated more closely with immune activity, for example, could be more useful for research into immune-related ageing than one that primarily reflects metabolic changes.

The researchers also developed new measures called transcriptomic ageing gene scores, or TAGS, based on the molecular patterns identified in their analysis.

According to the study, TAGS in several cases performed better than the ageing clocks alone when predicting health outcomes. These included frailty, walking speed, heart disease, diabetes, lung disease and mortality.

T. Em Arpawong, a research associate professor at the USC Leonard Davis School of Gerontology, said ageing is not determined simply by chronological age but also by biological changes taking place inside cells.

Senior author Eileen Crimmins said the study helps explain what is happening beneath the surface when biological ageing tests produce their results.

By identifying the molecular processes associated with individual ageing clocks, researchers may be able to interpret their readings more accurately and understand which tools are best suited to different areas of ageing research.

The findings could eventually support research into preventing age-related illness and identifying people at higher risk of declining health. However, the study focuses on biological markers and does not mean the new measures are ready to replace clinical assessments of health or provide individual predictions of lifespan.

Researchers said the work provides a clearer picture of the biological mechanisms captured by ageing clocks and could guide their use in future studies of ageing and disease.

Taking the stairs instead of using a lift could significantly reduce the risk of cardiovascular disease and premature death, according to a major study examining the health benefits of regular stair climbing.

Researchers from the University of East Anglia and Norfolk and Norwich University Hospital found that people who regularly climbed stairs had a 39 percent lower risk of dying from cardiovascular disease than those who rarely used stairs. They also had a 24 percent lower risk of death from any cause.

The study found that regular stair climbing was also associated with a lower risk of developing serious cardiovascular conditions, including heart attacks, strokes and heart failure.

The research team analysed health data from more than 480,000 people aged between 35 and 84. The findings were based on nine high-quality studies, with participants followed for a median period of 14 years.

Vassilios Vassiliou of Norwich Medical School at the University of East Anglia said stair climbing was a practical way to add physical activity to everyday routines. He described it as an activity that is often overlooked despite being easy to perform without special equipment or facilities.

Unlike structured exercise at a gym, climbing stairs can be included naturally in daily activities at home, at work or while travelling. Sophie Paddock, also from Norwich Medical School, said the activity could be particularly useful for people who have limited time or do not have convenient access to exercise facilities.

The researchers said even short periods of stair climbing several times a week could provide measurable health benefits. The activity can improve cardiorespiratory fitness and help lower cholesterol, both of which are linked to better cardiovascular health.

The amount of stair climbing also appeared to matter. Some of the studies reviewed by the researchers found that people who climbed more stairs generally experienced greater health benefits. However, even smaller amounts of activity were associated with positive changes.

The findings are particularly relevant as more than a quarter of adults worldwide do not meet recommended levels of physical activity. The researchers said encouraging simple forms of movement in everyday environments could help address this problem.

Workplaces, homes and public buildings could all play a role by making stair use easier and more appealing. Choosing stairs over lifts when possible may provide an accessible form of physical activity without requiring people to set aside additional time for a workout.

The findings were presented at a scientific congress of the European Society of Cardiology. Researchers said the results highlight how small changes in daily routines can contribute to better long-term health and may help reduce the burden of cardiovascular disease.

Children who spend much of their school day playing alone may not necessarily be lonely or unhappy, according to a new study from researchers at the University of Georgia in the United States.

The research suggests that some children simply enjoy their own company while maintaining satisfying friendships and a sense of belonging among their classmates. Researchers say the key factor may not be how often a child chooses to be alone, but whether they still feel connected to others.

The study involved 473 children aged between nine and 11 at several elementary schools in Georgia. Participants were asked to identify classmates who often played alone despite getting along with other students. They also answered questions about the importance they placed on belonging and their satisfaction with friendships and relationships within their classes.

Researchers found a clear difference between children who preferred solitude while still valuing social connections and those who placed little importance on belonging to a peer group.

Children who enjoyed spending time alone but considered belonging important generally reported being satisfied with both their close friendships and wider relationships at school. Researchers said these children may accept enough invitations to remain socially connected while choosing to spend some of their free time alone.

Rachael Pfanz, the study’s corresponding author and an elementary school psychologist, said these children can prefer doing their own activities without having difficulty getting along with classmates.

The findings were different for children who did not consider belonging important. They were more likely to report weaker relationships with friends and classmates.

Researchers warned that repeatedly turning down invitations can eventually affect a child’s social opportunities. Classmates may stop asking them to join activities, potentially leaving them with fewer chances to develop or maintain friendships.

Michele Lease, a professor of educational psychology at the University of Georgia and a co-author of the study, compared social interaction with other activities that benefit people even when they may not always feel like participating.

The researchers said adults should avoid assuming that every child who plays alone needs to be encouraged to join a large group immediately. Pressuring a child into a busy activity could make the situation uncomfortable rather than helping them build connections.

Instead, adults could introduce children to smaller groups or classmates who share similar interests. A child who enjoys drawing, reading, building or another individual activity may find it easier to connect with peers who have the same interests.

Pfanz said joining a large playground game, such as soccer, may feel overwhelming for a child who already prefers playing alone.

The researchers said the findings are particularly relevant to fourth- and fifth-grade students, a period when friendship groups become more established and children become better at recognising whether classmates are choosing solitude or experiencing social exclusion.

The study suggests that solitude itself should not automatically be viewed as a problem. What may matter more is whether children have meaningful relationships and continue to feel that they belong.