Inflammation. In the moments after an infection sets in, a bone is broken, or a nail punctures your foot, you need it. Each of those injuries requires a different deployment of the inflammation response.
Inflammation fights a virus by opening blood vessels to rush germ-fighting cells and chemical alarm signals to the infected area, which traps the virus and stops it from multiplying.
Inflammation is the first phase of fracture healing. It starts immediately after a bone breaks and lasts for a few days up to one week. Torn blood vessels bleed to form a blood clot, called a hematoma, which protects the area and builds a temporary bridge for new tissue growth.
Wound inflammation is a crucial part of the body’s natural healing process. It represents the body’s initial response to injury and aims to eliminate harmful agents, clear out damaged tissues, and set the stage for repair.
There’s another kind of inflammation. You’ve heard about it, read about it, maybe you’ve even gotten tested for it.
Here’s the distinction almost nobody explains to you: the inflammation above — the swollen ankle, the fever, the angry red cut — is a fire alarm. Loud, obvious, and it goes quiet once the danger’s handled. That’s not the fire I’m talking about today.
I’m talking about the one smoldering behind the drywall. No alarm, because nothing in your annual physical is built to detect it. It doesn’t announce itself with a symptom you can point to. And here’s the part that makes it genuinely sneaky: it doesn’t burn the same room in every house. In one woman, it shows up as gut chaos. In another, joint pain that gets waved off as “just getting older.” In another, it’s quietly working on cardiovascular risk. And in some, it finds its way to the brain.
That’s the fire I want to spend the next two weeks on — what it is, why your bloodwork almost certainly isn’t catching it, and what determines which room in you it ends up in.
When the Warnings Don’t Line Up
Start with a fact that should sound familiar if you’ve been reading me for a while: nearly half of the people hospitalized for a heart attack had LDL cholesterol under 100 mg/dL — the level national guidelines call optimal. Almost three-quarters fell within recommended cholesterol targets altogether. “Normal” cholesterol and a heart attack, in the same body, at the same time. The house looked fine from the outside.
Now here’s a stranger version of the same problem, and where we’re headed with this series. Roughly 30% of older adults are walking around with brains that have enough amyloid plaque or tau tangles — the physical hallmarks doctors look for at autopsy to diagnose Alzheimer’s — to qualify for the diagnosis. And they have no dementia. No memory loss, no confusion, nothing. Researchers at Vanderbilt are now running the largest study ever attempted to figure out why some brains carry the disease’s fingerprints and never suffer for it.
Plaques and tangles are scorch marks — evidence a fire was there. They’re necessary for an Alzheimer’s diagnosis; you basically never see the disease without them. But what science is learning is that they’re not sufficient. Having them doesn’t guarantee dementia — or in terms of my analogy, that the house burns down. Something else decides who crosses that line, and it’s the same something that decides whether your fire ends up in your gut, your joints, your heart, or your brain in the first place.
The Science of “Inflammaging”
There’s a term researchers coined for this: inflammaging — chronic, low-grade inflammation that tends to build with age, distinct from the acute, alarm-triggering kind that resolves once it’s handled; the broken bone, the nail in your foot.
With inflammaging, age is a driver, but it’s not a life sentence. Recent immunology research describes it as “rather than an inevitable decline… a process that can be reshaped,” tied as much to diet, movement, gut health, and stress as to the number of candles on your cake. This kind doesn’t resolve on its own the way a cut does — it just smolders until something shifts it, in either direction. According to Harvard Health, it’s estimated to affect over a third of American adults and is believed to contribute to more than half of all deaths worldwide by driving the age-related diseases we’re all trying to outrun — heart disease, cancer, diabetes, and yes, the neurodegenerative diseases we’ll get into next week.
Here’s why it matters even though you can’t feel it: this isn’t inflammation just sitting idle. Cells that stop dividing properly but don’t die off — scientists call this senescence — don’t quietly retire. They pump out their own steady stream of inflammatory chemicals, which damage the healthy cells around them, which triggers more of the same. It’s a slow, self-feeding cycle of cellular wear that compounds quietly for years, doing real damage long before anything shows up on a scan or in how you feel.
And that’s the part that should make you sit up: you cannot feel it. There’s no symptom checklist for silent inflammation, because it doesn’t show up the same way twice. It just works, quietly, wherever it finds the least resistance in you — which is exactly why one woman’s fire becomes IBS and another’s becomes brain fog.
Why Your Bloodwork Won’t Catch It
If you’ve had a physical in the last few years, you may have had a CRP test. C-reactive protein is a protein your liver produces in response to inflammation, and it’s most often used to gauge the kind caused by a major infection, an autoimmune flare, or a post-surgical complication. It’s useful — but it’s nonspecific: an elevated result confirms inflammation is present, not what’s causing it or where it’s coming from.
There’s a more sensitive version, hs-CRP, or high-sensitivity CRP, which measures the same protein at much lower concentrations. It’s often positioned as a cardiovascular risk marker, and there’s real backing for that: the American College of Cardiology’s late-2025 scientific statement counts hs-CRP as an additional way to help identify who’s at higher risk.
What hs-CRP can’t do is prove the CRP molecule itself is the problem. As Johns Hopkins Medicine puts it, currently there’s no evidence CRP itself is a driving force of atherosclerosis — it signals that low-grade inflammation is present in the vessel wall, not what’s causing the damage there. And whether that extra sensitivity meaningfully changes outcomes for someone who isn’t already high-risk is genuinely still unsettled in the research.
Either way, both versions share the same core limitation, and it’s the one that matters most for this series: sensitive but not specific. Good at telling you a fire exists somewhere in the house. Not built to tell you which room. Your gums, an old joint injury, your gut, or your brain could all trip the exact same number. One smoke detector, whole house, no room number.
The Firewall That Isn’t Always Fireproof
Your body actually has a few of these room-to-room barriers — your gut lining is one, keeping what’s inside your intestines from getting into general circulation. Your brain has its own version, called the blood-brain barrier: a tightly regulated boundary meant to keep your brain’s environment separate and protected from whatever’s circulating in the rest of your blood. For a long time, that made the brain feel like it was fireproof — off-limits to whatever inflammatory chaos was happening elsewhere.
It isn’t. When inflammatory signals build up systemically — cytokines like IL-6 and TNF-alpha, the same molecules hs-CRP is indirectly responding to — they can compromise that barrier’s integrity and cross it. Once inside, they activate the brain’s resident immune cells, called microglia, and put them into an inflammatory state. Chronically activated microglia are now understood to be central players in how neurodegenerative disease actually develops and progresses.
So the fire doesn’t have to start in your brain to end up burning there. It can start in your gut, your gums, or your blood sugar, breach a wall it was never supposed to get past, and keep going. For some women, that’s exactly where it ends up. For others, it stays out of the brain entirely and does its damage elsewhere. Next week is about the version that reaches the brain — but this fire is never only a brain story, and I don’t want you walking away thinking it is.
One More Piece of the Puzzle
If you’ve read my two-part series on hormone replacement, you already know estrogen isn’t just a reproductive hormone — it has real anti-inflammatory effects throughout the body, brain included. When estrogen drops during perimenopause and menopause, some of that natural inflammatory dampening drops with it. It’s not the whole story here, but it’s one more reason this particular window of life is worth paying closer attention, not less.
Next Week
We’re going to follow this fire specifically into the brain: what’s actually driving it there — your gut, your gums, your blood sugar, and a blood marker almost nobody tests for called homocysteine — and what the real evidence says about its connection to Alzheimer’s, Parkinson’s, and beyond. Plus, the two tests worth asking for that will actually tell you something your annual physical won’t.
