Does your immune system really weaken as you age, and is there anything you can do about it?
Your immune system demonstrably weakens with age, but there is currently no proven intervention that reliably reverses that process. Keep your vaccinations up to date and follow developments around agents targeting senescent cells, as clinical evidence for these is still lacking.
Yes, your immune system really does weaken as you age. Scientists call this immunosenescence, a gradual decline in your defences that increases the risk of serious infections, cancer, dementia and cardiovascular disease. A central cause is that your thymus, the organ where immune cells mature, steadily shrinks. As a result, fewer fresh immune cells are produced, while the proportion of old 'memory' cells grows disproportionately. The cells that clear tumours and infected cells also work less effectively, even though their numbers actually increase.
Alongside this weakening, a second process is at work: inflammaging. This is a smouldering, low-grade inflammation present throughout the body even in the absence of any visible disease. It is regarded as an independent risk factor for virtually all major age-related diseases. Changes in the gut microbiome have been named as a possible driving factor, but that link has not yet been studied enough to draw firm conclusions.
Immune ageing does not affect everyone at the same pace. Measurements at the cellular level reveal large individual differences: two people of the same age can be immunologically decades apart. Centenarians show that the immune system sometimes adapts remarkably well to advanced age, although we do not yet know exactly what protects them. Men and women also age immunologically in different ways, leading to differing susceptibility to age-related diseases1,2,3,4,5,6,7,8.
What can you do about it yourself? Honestly, the evidence is limited at this point. Agents that target senescent cells or suppress their harmful secretions are being investigated, but no human studies have yet shown them to be safe and effective. BCG vaccination showed signs of immunological rejuvenation in one type of immune cell in some individuals in early, exploratory research, but that is not proof that vaccination structurally rejuvenates your immune system. The same research suggests that a severe infection such as COVID-19 can temporarily increase the biological age of your immune system, but that effect diminished after recovery. In short, there is currently no proven treatment that reliably reverses immune ageing.
Based on multiple review articles and mechanistic studies (PMID 37179335, 34391943, 33551332, 39395575, 35326467, 31986068, 40044970, 37175491). The description of immune ageing and low-grade smouldering inflammation rests on strong, consistent evidence from human studies. The intervention data on agents that target senescent cells and on BCG vaccination are limited and early-stage experimental.