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.
Organs do not age at the same pace in the same person. Research based on blood proteins in tens of thousands of people shows that the immune system, the heart, the brain and the kidneys each have their own ageing rate that differs measurably from one another.
The immune system and the heart both illustrate what is at stake when they age faster than the rest of the body. In the Whitehall II study (more than 6,200 participants, followed for twenty years), an ageing immune system carried a hazard ratio of 1.36 for developing multiple diseases simultaneously across different organs. An ageing heart gave a hazard ratio of 1.52 for that same multimorbidity, and for chronic heart failure it was 1.65. Both organs are therefore at risk, but in different ways and with different outcomes.
The immune system has something particularly notable about it: together with the brain, it is the only organ that is clearly associated with a longer lifespan. In a study of 44,498 participants from the UK Biobank, people with both a 'youthful' immune system and youthful brain had a 56% lower risk of death than average. Individually, a youthful immune system and youthful brain each gave a comparable halving of that risk (hazard ratio around 0.58 and 0.60 respectively). The heart did not stand out in that analysis.
Chronic low-grade inflammation can widen the ageing gap between organs. An artificial intelligence-based inflammation measure, derived from blood immune data of more than a thousand people, predicted both cardiac ageing and frailty. A specific protein produced by immune cells turned out to be the strongest driver of arterial calcification in this model. In cell and mouse experiments, damage to the arterial wall was partly reversed by switching off that protein, but whether this also works in humans has not yet been studied.
All these associations are observational: the studies measure correlation, not cause and effect. Men age faster than women in most organs, and lifestyle, diet and medication are associated with the rate of ageing per organ, although the direction varies by factor and by organ.
All claims are based on large observational cohort studies (UK Biobank, Whitehall II, Chinese and American cohorts) and one smaller Spanish study. Causal relationships have not been established. The iAge findings on heart-immune interaction are partly supported by cell and animal research.
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.
Can you slow down the ageing of your immune system?
The immune system demonstrably ages, and there are promising avenues for slowing that process, but no single approach has been proven safe and effective in humans. Eating less processed food is the only step you can concretely take right now; everything else requires more research in humans before any conclusions can be drawn.
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.
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.
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.