Cells do not work alone.
They constantly send and receive messages. These messages help the heart, brain, muscles, immune system and other organs work together.
Some messages travel through hormones. Others come from the nervous system or the immune system. Together, they tell cells when to grow, use energy, respond to infection, repair damage or slow down.
As we age, this communication may become less clear and less well coordinated.
Scientists call this altered intercellular communication. The word intercellular simply means between cells.
The change can happen in several ways. Some signals may become weaker. Others may remain active for too long. Cells may also respond less accurately to the messages they receive.
One important example is long-lasting, low-level inflammation.
Inflammation is a normal defence response. It helps the body fight infection and repair an injury. But when inflammatory signals remain active for too long, they may begin to disturb healthy tissues.
Age-related changes in hormones and the immune system can also affect appetite, sleep, muscle maintenance, blood glucose and the way the body responds to stress.
This does not mean that one hormone test or one inflammation marker can show how well the whole body is communicating.
The body uses many overlapping signalling systems. A result must always be understood together with symptoms, medical history, physical function and other health information.
Altered communication also connects with the other Hallmarks of Ageing.
Damaged mitochondria can release signals that promote inflammation. Senescent cells can affect nearby tissues. Changes in the way cells use nutrients can alter the messages that control energy and repair.
This helps explain why ageing cannot be understood by looking at one organ or one laboratory result alone.
For the reader, the practical message is not to search for a single treatment that “resets” every signal.
Regular physical activity helps muscles, metabolism and the immune system respond more effectively. Good sleep supports hormonal and immune regulation.
Not smoking and controlling blood pressure, blood glucose and cholesterol reduce sources of long-term stress on tissues.
Vaccination and appropriate treatment of chronic disease also help prevent repeated or unnecessary immune activation.
We cannot keep every biological signal perfectly young.
But we can protect the systems that allow cells, tissues and organs to respond to one another in a coordinated way.
