Inflammaging — the chronic low-grade inflammation that drives aging

He called the phenomenon inflammaging, and proposed that chronic low-grade inflammation was not merely a consequence of aging but one of its central drivers. Two decades of subsequent research have not refuted that idea. They've deepened it.

Inflammaging is not the same as the acute inflammation that follows an infection or injury. Acute inflammation is a calibrated response: a pathogen or wound triggers cytokine release, immune cells flood the site, damaged tissue is cleared, pathogens are neutralized, and the inflammation resolves. The resolution is as important as the onset — a healthy inflammatory response has a beginning, a middle, and an end. Inflammaging has no end. It is baseline, circulating, persistent. It produces no fever, no visible swelling, no single symptom you can point to. It simply hums, and as it hums, it accumulates damage across every tissue it touches.

The sources of inflammaging are multiple and they reinforce each other in ways that make attribution — and therefore intervention — complicated. Senescent cells are one major contributor. Cellular senescence is the state a cell enters when it sustains damage beyond repair but resists apoptosis — programmed cell death. Senescent cells stop dividing, which sounds harmless, but they adopt a secretory phenotype called the SASP: the Senescence-Associated Secretory Phenotype. SASP cells release a cocktail of inflammatory cytokines, matrix metalloproteinases, and growth factors that chronically activate neighboring immune cells and create a localized inflammatory microenvironment. One or two senescent cells in a tissue are manageable. As the body ages and senescent cell burden accumulates — because senescence induction increases with age and the immune clearance of senescent cells becomes less efficient — the SASP becomes a systemic inflammatory signal. This is the connection between cellular senescence and inflammaging, and it's one of the reasons senolytics — compounds that selectively eliminate senescent cells — have generated so much longevity research interest.

The gut microbiome is a second major contributor, and its role in inflammaging is increasingly well-characterized. The diversity of the gut microbiome declines with age. Populations of bacteria that support epithelial barrier integrity, produce short-chain fatty acids, and modulate immune tone decrease. Populations associated with inflammatory signaling and LPS (lipopolysaccharide) production increase. The gut epithelium, already thinned by decades of suboptimal nutrition and stress, becomes more permeable — a phenomenon commonly called leaky gut. LPS, a structural component of gram-negative bacterial cell walls, crosses the compromised barrier in small amounts and enters systemic circulation. Even tiny amounts of circulating LPS activate TLR4 receptors on immune cells and drive cytokine production. The result is a persistent low-level inflammatory signal that originates in the gut but spreads systemically, detectable as elevated CRP and IL-6 in otherwise apparently healthy older adults.

Mitochondrial dysfunction contributes through a different mechanism: the release of mitochondrial DNA, or mtDNA, into the cytoplasm and eventually the circulation. Mitochondria are evolutionary descendants of bacteria, and their DNA retains molecular patterns that the innate immune system recognizes as foreign — specifically, the DAMP (damage-associated molecular pattern) system. When damaged or dysfunctional mitochondria release mtDNA, the cGAS-STING pathway detects it and activates type I interferon responses and inflammatory cytokine production. This is why mitochondrial quality matters not just for energy production but for immune tone: poorly maintained mitochondria are a chronic inflammatory stimulus. The decline in mitochondrial biogenesis, turnover quality, and membrane integrity that characterizes aging translates directly into inflammaging through this pathway.

Accumulated protein damage, immunosenescence, and epigenetic dysregulation complete the picture. Immunosenescence — the functional decline of the immune system with age — produces a paradox: the immune system becomes simultaneously less effective at clearing pathogens and more prone to generating nonspecific inflammatory activity. The regulatory mechanisms that normally keep immune activation proportional to actual threats become dysregulated. The result is an immune system that under-responds to novel pathogens while chronically over-activating on background signals it can no longer properly resolve.

The downstream consequences of inflammaging are not subtle. Cardiovascular disease is perhaps the most thoroughly documented: elevated IL-6 and CRP are independent predictors of cardiovascular events, not because inflammation causes atherosclerosis in isolation, but because inflammatory cytokines drive endothelial dysfunction, promote foam cell formation in arterial walls, destabilize plaques, and promote the coagulation cascades that turn stable plaques into acute coronary syndromes. Neuroinflammation — the central nervous system's version of inflammaging, driven by microglial activation and astrocyte reactivity — has strong connections to Alzheimer's disease, Parkinson's disease, and the cognitive decline that accumulates through midlife. TNF-α and IL-1β, two major inflammaging cytokines, directly impair synaptic plasticity and hippocampal neurogenesis. The research connecting systemic inflammation to cognitive trajectory is now substantial enough that inflammatory status is considered in serious longitudinal aging research alongside standard metabolic markers.

Sarcopenia — the progressive loss of muscle mass and function with age — has a major inflammatory driver. IL-6 at chronically elevated levels activates catabolic pathways in skeletal muscle, suppresses IGF-1 signaling, and promotes muscle protein breakdown. The person who is eating adequate protein, doing resistance training, and still losing muscle faster than expected may be fighting an inflammaging-driven catabolic state that the protein and training alone can't fully offset. Metabolic dysfunction — insulin resistance, visceral fat accumulation, metabolic syndrome — is bidirectionally connected to inflammaging: adipose tissue, particularly visceral adipose, is itself an endocrine and paracrine source of inflammatory cytokines, and inflammaging worsens insulin signaling, driving further fat accumulation in a self-reinforcing cycle. Frailty, the clinical syndrome of vulnerability and physiological reserve depletion that dramatically increases mortality risk in older adults, now has inflammaging at its mechanistic center in much of the geriatric research literature.

The peptide and intervention landscape for inflammaging operates at multiple levels. BPC-157, a synthetic gastric peptide, has been studied extensively in rodent models for its anti-inflammatory effects on gut and systemic tissue, including effects on inflammatory cytokine profiles; the human evidence is limited but it is among the most-studied peptides in the preclinical anti-inflammatory space. KPV, the alpha-MSH-derived tripeptide, reduces NF-κB signaling and downstream cytokine production in multiple tissue models; its anti-inflammatory effects are primarily being researched in gut mucosal and skin contexts. Thymosin Alpha-1, studied in the context of immune reconstitution and viral hepatitis in clinical settings where it has regulatory approval in several countries, has immune-modulatory properties that include reducing inflammatory cytokine imbalance and supporting T-regulatory cell function. VIP reduces IL-6 and TNF-α production from activated immune cells through VPAC receptor signaling, with anti-inflammatory effects studied in autoimmune and inflammatory bowel models.

The mitochondrial angle connects to SS-31 (elamipretide), a mitochondria-targeted antioxidant peptide that reduces mitochondrial oxidative stress and stabilizes cardiolipin in the inner mitochondrial membrane, reducing the mtDNA leakage that activates STING and drives inflammaging through that pathway. SS-31 is in clinical trials for heart failure and mitochondrial disease; its role in inflammaging per se is a research-stage investigation. MOTS-c, the mitochondria-derived peptide that activates AMPK, has anti-inflammatory properties beyond its metabolic effects, including modulation of the STING pathway, which again positions mitochondrial signaling peptides at the intersection of energy metabolism and immune tone. NAD+ restoration — through precursors including NMN and NR — supports mitochondrial function and may reduce the inflammaging contribution from mitochondrial dysfunction through maintained mitophagy and biogenesis; this is an active research area with some human evidence for the metabolic effects of NAD+ precursors, though their specific impact on inflammaging markers in humans is still being studied.

Before any of the peptide or senolytic strategies, the most consistent evidence for lowering inflammaging markers points to foundational habits. Sleep is among the most direct levers: even modest sleep restriction raises circulating IL-6 and CRP in controlled studies, and restoring adequate, consolidated sleep tends to bring those markers back down, because the deep stages of sleep are when much of the body's inflammatory regulation and clearance occurs. Regular physical activity, particularly when it combines aerobic work with resistance training, lowers baseline inflammatory tone over time; the acute spike in cytokines that exercise produces is followed by an adaptive downregulation that leaves chronic IL-6 and CRP lower in active people than in sedentary ones. Omega-3 fatty acids — EPA and DHA from fatty fish or supplementation — provide the substrate for the body's own pro-resolving signaling molecules and have been studied for measurable reductions in inflammatory markers. And chronic psychological stress, through sustained cortisol and sympathetic activation, raises inflammatory signaling, so practices that regulate the stress response have been researched for their capacity to lower the same markers. None of these are exotic, and none require a prescription, but they act on the same IL-6 and CRP signals that the cellular-level interventions target, which is why they remain the first layer of any serious approach to inflammaging.

What ties this landscape together is a shift in framing. If chronic, low-grade inflammation is a driver of aging rather than merely a byproduct of it, then markers like IL-6 and CRP become some of the more meaningful signals of how a body is actually aging — and the interventions researched to lower them, from foundational habits to peptides and senolytics studied at the cellular source, may matter as much for long-term healthspan as for any single disease. The inflammation that hums quietly in the background is, on this view, worth taking as seriously as the conditions it helps set in motion.