Does your immune system really weaken as you get older, and can you do anything about it?
Your immune system demonstrably weakens with age, but eating healthily and exercising can reduce the smouldering inflammation that accompanies it. It is still too early to rely on drugs targeting senescent cells.
Yes, the immune system genuinely weakens with age. Both the fast, innate response and the more targeted, adaptive immunity decline. Older people respond less well to vaccines, become more susceptible to infections, and when they do fall ill, the course of disease is more often serious. This has been broadly documented across multiple cell types and organs.
There is also a paradoxical phenomenon at work: while the immune system becomes less alert to acute threats, a smouldering inflammation burns inside the body at the same time. This chronic low-grade inflammation, often called 'inflammaging', is associated with a greater risk of cardiovascular disease, cancer and dementia. Higher blood levels of inflammatory substances are measurable in older people and correlate with frailty and multiple simultaneous diseases.
Several mechanisms underlie this decline. The thymus, the organ that trains new immune cells, shrinks considerably as you age. As a result, fewer 'fresh' cells are produced that can recognise new pathogens. At the same time, the cells that make antibodies function less well in older people. The gut microbiome also plays a role: a disrupted microbiome can sustain chronic inflammation. And greater amounts of fat tissue, which increase with age, contribute to this as well.
What can you do about it? Eating healthily and exercising regularly are the best-supported approaches for reducing inflammaging. The evidence is encouraging, though researchers are cautious about the precise magnitude of the effect. Research is also being conducted into drugs that target senescent cells, but the evidence in humans is still limited and safety has not been fully established. That option is therefore not yet ready for practical use.
Centenarians show that the picture is not the same for everyone. They appear to be better able to adapt their immune system, suggesting that the degree of immune ageing is partly modifiable. What lessons this holds for the rest of the population, however, remains uncertain.
Claims are based on multiple reviews and mechanistic studies (PMID 37179335, 34391943, 35983061, 39395575, 33551332, 33021823, 38052484, 34888528). For lifestyle interventions the evidence is encouraging but does not come from large randomised trials with hard endpoints. For senolytics, the evidence in humans is still thin.
Does your immune system really weaken as you get older?
Your immune system does indeed weaken as you get older, but how quickly that happens varies considerably from person to person. Lifestyle factors play a role in this, although little has yet been proven specifically for humans.
Can you slow down the ageing of your immune system?
You can partly limit the consequences of an ageing immune system, especially with more cleverly designed vaccines such as adjuvant-enhanced flu vaccines and possibly the shingles vaccine. Whether you can slow the ageing process itself remains an open question.
Does spending more time outdoors help your immune system as you get older?
Spending more time outdoors may support your immune system as you get older, mainly through improved vitamin D production, but whether this actually leads to less illness has not yet been conclusively demonstrated. How polluted the outdoor air is also matters: in areas with serious air pollution, being outside can in fact be detrimental.
Which factors weaken your immune system?
Several factors demonstrably weaken your immune system: deficiencies in vitamin A, zinc and iron are the best supported, but medical treatments, chronic stress and strenuous exercise also play a role. When using high-dose steroids medically or in the case of an HIV infection, it is advisable to involve your doctor in infection prevention.
Does your immune system age at a different rate than your heart?
Yes, your immune system and heart age at measurably different rates, and an ageing immune system is more strongly associated with a longer lifespan than the heart is. These are associations, not causal evidence, but that is reason enough to take both seriously.
Does exercise help your immune system as you age?
Regular, moderate exercise helps your immune system by reducing smouldering inflammation. Suddenly training very hard without a gradual build-up can actually temporarily lower your immune defences.