Chronic inflammation (inflammaging)

Inflammation is supposed to be a short, sharp emergency response that clears an infection and then shuts off. With age it stops shutting off — settling into a low, simmering, body-wide hum that no longer has any germ to fight. This "inflammaging" is now seen as one of the central engines of age-related disease, tying together heart disease, diabetes, and dementia through a single shared mechanism. The good news is that it is unusually responsive to ordinary levers: diet, exercise, sleep, and stress management measurably turn the dial down.

Chronic inflammation, or inflammaging, is the eleventh of the twelve hallmarks of aging — an integrative hallmark, meaning it is less a root cause than a systemic consequence that then feeds back to accelerate everything upstream of it. Acute inflammation is one of the body's most useful tools: a self-limiting response that destroys pathogens, clears debris, and triggers repair, then resolves. Inflammaging is what happens when that program never fully switches off — a sterile (germ-free), low-grade, persistent inflammatory state that pervades the tissues of older bodies and acts as both a symptom of aging and an active accelerant of it.^[1]

What makes it "sterile," and why that matters

The defining oddity of inflammaging is that there is nothing to fight. Classic inflammation is launched when the immune system detects a pathogen. Inflammaging is launched by the body's own damaged components — molecules released by stressed and dying cells that the immune system mistakes for an infection. These internal alarm signals are called damage-associated molecular patterns (DAMPs), and the master switch they flip is a transcription factor called NF-κB, which coordinates the cell's entire pro-inflammatory program.^[2]

In a young body, NF-κB flares briefly and then resolves. In an aging body, the upstream alarms never stop ringing, so NF-κB stays chronically switched on.^[3] That persistent, purposeless activation is the heart of the problem — and because the signals travel in the bloodstream, a process that begins as scattered local damage becomes a body-wide inflammatory tone.

The sources all converge

Inflammaging is not driven by one thing. It is the sum of several age-related failures that each pour the same inflammatory fuel into circulation, which is exactly why it sits at the integrative tier of the hallmarks framework.

Zombie cells. Senescent cells — damaged cells that stop dividing but refuse to die — secrete a continuous inflammatory cocktail (the senescence-associated secretory phenotype, SASP) that both inflames the local tissue and converts healthy neighbours into more senescent cells. This is one of the largest single contributors; the full mechanism is covered under cellular senescence.^[4]
Leaked mitochondrial DNA. As the cell's power plants (mitochondria) accumulate damage and are cleared too slowly, they spill their own DNA into the cell interior. Because that DNA structurally resembles bacterial DNA, internal sensors — the cGAS-STING pathway and the NLRP3 inflammasome — read it as an infection and fire, a thread that also runs through genomic instability.^[5]
An aging immune system. With age, blood-cell production skews toward pro-inflammatory cell types, the thymus shrinks and stops making fresh naive immune cells, and the immune repertoire fills with exhausted, senescent-like T-cells that have lost their ability to clear pathogens but pump out inflammatory cytokines. This immunosenescence both fuels inflammaging and is worsened by it.^[6]
Visceral fat. Fat stored around the organs is an active inflammatory organ. As it expands, its resident immune cells switch from an anti-inflammatory to a pro-inflammatory state and secrete cytokines like IL-6 and TNF-α directly into the bloodstream.^[7]
A leaky gut. The intestinal barrier weakens with age, letting fragments of gut bacteria (lipopolysaccharide, a potent inflammatory trigger) cross into the circulation, where they continuously prod the innate immune system.^[8]

No single one of these explains inflammaging. Together they sustain it.

How systemic inflammation becomes disease: the cardio-metabolic-brain axis

The reason inflammaging matters clinically is that it does not stay abstract — it converges on a shared pathway linking metabolic dysfunction, blood-vessel damage, and brain decline. The hinge is insulin resistance and the health of the cells lining blood vessels (the endothelium).^[9]

In a healthy vessel, insulin signalling tells endothelial cells to produce nitric oxide, the molecule that relaxes and widens arteries, keeps blood from clotting inappropriately, and holds inflammation in check. Chronic inflammation selectively breaks the arm of insulin signalling that makes nitric oxide while leaving intact the arm that drives constriction — so vessels lose their relaxant and tilt toward stiffness, higher blood pressure, and the recruitment of inflammatory cells into the artery wall, where they help build atherosclerotic plaque.^[10]^[11] This is the mechanistic bridge from a diffuse inflammatory state to the hard cardiovascular outcomes covered under cholesterol and blood pressure.^[12]

The same circulating cytokines reach the brain. They degrade the blood-brain barrier — the tight seal that normally keeps the brain's environment separate from the blood — allowing inflammatory molecules and immune cells to leak into brain tissue. There they activate the brain's resident immune cells (microglia) into a self-perpetuating inflammatory state, and they induce insulin resistance in the brain itself, starving high-demand memory regions of fuel and promoting the tau and amyloid changes associated with Alzheimer's disease.^[13]^[14] This shared inflammatory-metabolic root is why the same lifestyle pattern tends to protect heart, metabolism, and brain at once — the territory of dementia prevention.

Measuring it

Inflammaging can be tracked, which makes it one of the more actionable hallmarks. The everyday clinical markers are high-sensitivity C-reactive protein (hs-CRP) and the cytokine IL-6, both cheap blood tests of baseline inflammatory tone. A second, almost free marker is the neutrophil-to-lymphocyte ratio (NLR) — calculable from any standard blood count — which rises with systemic stress, immune aging, and frailty.^[15]^[16] Because single markers are noisy, researchers increasingly combine several into composite scores, and have built "inflammatory clocks" (such as iAge) that read an entire cytokine network to estimate immune age.^[17] The widely used epigenetic clock GrimAge has a second version that explicitly folds in a methylation-based estimate of CRP, directly tying epigenetic age to inflammatory status.^[18]

The single most striking finding in this area is how powerful a plain inflammation score is. In a large study within the US Health and Retirement Study, a composite of seven inflammatory markers was a better predictor of four-year mortality than any of thirteen DNA-methylation epigenetic clocks — bettered only by chronological age itself. Inflammation correlated with epigenetic-age acceleration across most of those clocks, yet it still predicted death even after adjusting for them, implying it captures a distinct biological process.^[19] Inflammation also independently predicts the geriatric syndrome of frailty.^[20] For all the sophistication of the methylation clocks, a simple measure of how inflamed you are remains one of the strongest available reads on biological aging.^[21]

What actually lowers it

This is where inflammaging is most encouraging: it responds to behaviour, and the levers are the familiar ones. A recurring lesson, though, is that the inflammatory benefit often tracks with weight loss and overall dietary quality rather than any single magic food or fasting schedule — so the honest framing is "patterns, not tricks."

An anti-inflammatory dietary pattern. Composite patterns beat isolated supplements. In a meta-analysis of randomized trials, the Mediterranean diet significantly reduced circulating inflammatory markers versus control diets, while the DASH diet and vegetarian/vegan patterns did not reach statistical significance in the same comparisons — a useful reminder that "healthy-sounding" is not the same as "proven to lower inflammation."^[22] The practical version is the Mediterranean dietary pattern, and avoiding the pro-inflammatory drivers covered under ultra-processed food.^[23]

Two mechanisms inside that pattern are worth singling out. The marine omega-3 fats EPA and DHA do more than dampen inflammation — they are the raw material the body uses to build specialized pro-resolving mediators, signalling molecules that actively switch inflammation off and orchestrate clean-up, rather than merely blocking it.^[24] (See omega-3.) And dietary fibre feeds gut bacteria that ferment it into short-chain fatty acids like butyrate, which both calm immune signalling and fuel the cells of the gut lining — shoring up the barrier whose breakdown leaks bacterial fragments into the blood.^[25] Fermented foods support the same axis.

Caloric restriction — with an honest caveat on fasting. Sustained moderate calorie restriction has the best evidence: the 2-year CALERIE trial in healthy non-obese adults achieved a roughly 10% reduction in body weight and significantly lowered TNF-α, without harming bone or muscle beyond what weight loss predicts.^[26] The story for intermittent fasting is more equivocal: a 12-month trial found that time-restricted eating and standard calorie restriction produced similar weight loss but neither significantly changed inflammatory cytokines, and reviews suggest the anti-inflammatory effect of fasting appears mainly when substantial weight is lost.^[27]^[28] The takeaway: the energy deficit and fat loss are doing much of the work, not the clock.

Exercise — and the IL-6 paradox. This is the most counter-intuitive piece of the puzzle. IL-6 is usually a villain of inflammaging — yet contracting muscle releases a burst of IL-6 into the blood during exercise, and this muscle-derived IL-6 is anti-inflammatory, triggering the release of inflammation-resolving signals rather than the damaging trans-signalling pathway.^[29] Over time, regular training lowers baseline inflammation by shrinking visceral fat, calming inflammatory immune cells, and releasing beneficial muscle hormones (myokines such as irisin and BDNF) that even protect the brain.^[30]^[31] The dose-response is hormetic, though: a single bout of exhaustive endurance exercise lasting hours triggers a transient pro-inflammatory, immunosuppressed state, and chronic unrecovered overtraining can itself sustain inflammation — which is why recovery is part of the prescription, not an afterthought.^[32] The site covers the practical dosing under zone 2, VO₂ max, and resistance training.

Stress and sleep. Chronic psychological stress keeps the stress-hormone system switched on, and sustained cortisol exposure can make immune cells deaf to cortisol's normal anti-inflammatory feedback — removing one of the body's brakes on inflammation.^[33] Structured mindfulness-based stress reduction has lowered hs-CRP and other inflammatory markers in randomized trials, with a dose-response to practice time.^[34]^[35] Adequate, consistent sleep preserves the same anti-inflammatory feedback; the broader picture lives under stress and recovery.

The drug frontier

Several geroscience drugs target inflammaging upstream, but none is established for healthy adults, and all are covered in depth under geroprotectors.

Metformin, the long-standing diabetes drug, activates the cellular energy sensor AMPK and dampens NF-κB-driven inflammation; it is being tested for broad age-related disease prevention in the large TAME trial in non-diabetic older adults, which aims partly to establish "aging" as a treatable indication.^[36]^[37]
Rapamycin, given at low weekly doses to avoid the immune suppression of daily dosing, quiets the inflammatory secretome by inhibiting the mTOR pathway; the PEARL trial found weekly low-dose rapamycin safe in healthy older adults, with some sex-specific gains in lean mass — discussed under deregulated nutrient sensing.^[38]
Senolytics and senomorphics attack the SASP at its source — by clearing senescent cells or silencing their secretions. The human evidence (and the real cautions, including a study where the popular dasatinib+quercetin combination transiently accelerated an epigenetic-aging measure in healthy people) is laid out under cellular senescence.^[39]^[40]

What this does and doesn't tell you

What it tells you: inflammaging is a real, measurable, and consequential process — the convergence point where senescent cells, leaked mitochondrial DNA, an aging immune system, visceral fat, and a leaky gut all feed a single body-wide inflammatory state that drives cardiovascular, metabolic, and neurodegenerative disease through a shared axis. It is trackable with cheap blood tests, and a plain inflammation score rivals or beats sophisticated epigenetic clocks at predicting mortality. Most importantly, it responds to ordinary levers: a Mediterranean-pattern diet, omega-3s, fibre, regular (well-recovered) exercise, weight loss, sleep, and stress reduction all measurably lower it.

What it doesn't tell you: that any drug or supplement should be used to suppress inflammation for longevity in a healthy person. The pharmacological agents are promising but unproven for that purpose; fasting's anti-inflammatory effect appears to ride mostly on fat loss rather than the schedule itself; and inflammation is not simply "bad" — the acute, resolving kind is essential, and the goal is to restore its off-switch, not to abolish it. As with the other hallmarks, the elegance of the mechanism runs well ahead of the proven interventions, and the proven interventions are the unglamorous ones.