How Immunity Ages: Immunosenescence and What Helps

Immunity ages like the rest of us: slower learning, fading memory precision, smouldering background inflammation. Immunologists call the package immunosenescence — and it explains much of why respiratory infections grow more serious with age.

It also responds to intervention better than its reputation suggests.

What Changes Under the Hood

The thymus — T-cell academy — involutes from adulthood, shrinking naive-cell output; the memory repertoire narrows toward past encounters; antibody responses to NEW challenges (novel infections, first-time vaccines) weaken and arrive slower; and 'inflammaging' sets in — chronically elevated background inflammation (IL-6, CRP) that both damages tissue and distracts defence. Innate responders lose some killing sharpness too.

Why Respiratory Illness Bites Harder

The respiratory consequences compound: slower viral clearance extends illness; weaker barrier repair invites secondary bacterial pneumonia; diminished cough strength and ciliary pace (the airway's own aging, covered in our aging timeline) reduce mechanical defence — which is why influenza and pneumonia hospitalisation curves climb steeply past 65, and why vaccination schedules add enhanced and additional respiratory vaccines in later decades.

The Interventions With Evidence

Exercise is immunosenescence's best-documented counter: active older adults show better vaccine responses, lower inflammaging markers and — in cohort after cohort — fewer serious infections; strength work preserves the muscle that illness recovery draws on. Nutrition targets the age-specific gaps: protein (1.0–1.2 g/kg), vitamin D, B12 absorption, zinc adequacy. Sleep quality defends the overnight immune shift. Vaccination becomes MORE valuable, not less — enhanced formulations exist precisely because the stakes rose. And social connection correlates with immune resilience strongly enough that loneliness belongs on the risk list.

The Realistic Frame

Immunosenescence is a slope, not a cliff — and the slope's steepness is substantially behavioural. The 70-year-old exerciser with current vaccines, decent protein and good sleep carries a defence profile many sedentary 50-year-olds would envy.

For families: these habits are gifts that compound — and the household's own vaccination currency protects its most senior members most.