The age-related decline of immune function, termed immunosenescence, is one of the primary reasons why infectious diseases, cancers, and autoimmune conditions all increase in incidence after middle age. The thymus, which produces naive T cells, begins involuting in early adulthood and has typically lost 70 to 80 percent of its functional tissue by age 50. The result is a reduced output of new T cells capable of recognising novel pathogens, reduced diversity of the T cell repertoire, and a compensatory expansion of memory T cells that may be dysfunctional. Understanding immunosenescence matters because it is not simply an ageing process. Its rate is modifiable.
What Changes in the Ageing Immune System
Beyond thymic involution and T cell decline, several other changes characterise immunosenescence. Natural killer cell numbers increase with age but their cytotoxic activity per cell decreases. Macrophage function is impaired, with slower pathogen recognition and reduced phagocytic capacity. B cell antibody diversity declines, which is why older adults show poorer responses to novel antigens including new vaccines. Neutrophil function, particularly the ability to migrate to sites of infection, deteriorates. And chronic low-grade inflammation, termed inflammaging, creates a pro-inflammatory background that paradoxically impairs acute immune responses.
Exercise as Immune Preservation
Regular aerobic exercise is the most consistently documented lifestyle intervention for preserving immune function with age. A study by Duggal et al. at the University of Birmingham compared highly active older cyclists aged 55 to 79 with sedentary peers and younger control groups. The cyclists showed thymic output, T cell counts, and cytokine profiles comparable to young adults, while the sedentary older group showed the expected age-related immune decline. The cyclists were not genetic outliers. They were simply active.
Nutrition, Zinc, and Immune Preservation
Protein malnutrition is a major driver of immunosenescence in older adults, who often eat insufficient protein while their protein requirements are actually higher than those of younger adults due to anabolic resistance. Zinc deficiency, common in older adults, accelerates thymic involution and impairs T cell function. Adequate dietary protein, zinc, vitamin D, and polyphenol intake are the nutritional foundations of immune preservation with age. Caloric restriction in animal models extends immune function, but in older adults it more commonly produces sarcopenia and immunodeficiency than benefit.
- Maintain regular aerobic exercise: 150 minutes per week of moderate intensity is the minimum threshold for immune preservation
- Ensure dietary protein intake of 1.6 to 2g per kilogram of body weight: immune cell production requires amino acids
- Supplement vitamin D and maintain adequate zinc: both are commonly deficient in older adults and both are critical for immune function
- Avoid chronic psychological stress: it accelerates immune ageing beyond what chronological age alone predicts
- Consider annual influenza vaccination and keep immunisations current: the ageing immune system requires more robust vaccine stimulation
Sources
- Duggal, N.A., et al. (2018). Major features of immunesenescence, including reduced thymic output, are ameliorated by high levels of physical activity in adulthood. Aging Cell, 17(2), e12750.
- Pawelec, G. (2018). Age and immunity: what is immunosenescence? Experimental Gerontology, 105, 4-9.