A woman in her seventies undergoes a successful hip replacement. The surgery goes well. She is discharged on schedule. A month later, her daughter notices she's forgetting appointments she used to keep in her head. She's stopped reading her morning paper because she can't follow the articles. She seems vaguer in conversation. The family chalks it up to age.

A retired engineer recovers from cardiac surgery. He returns home, and the routines that have anchored his life for forty years — the morning crossword, the weekly chess game with his grandson — slip out of reach. He stops doing them. He doesn't say why. When his wife asks, he tells her he's just tired.

A grandfather sails through bowel surgery and, in the weeks that follow, becomes someone his family doesn't quite recognize. He forgets stories he's told a hundred times. He misses follow-ups. The family wonders whether something else is happening — whether the surgery has somehow "started" the dementia they were worried about.

In each of these cases, the most likely explanation is something with a clear name and a measurable biology — and most patients and families have never heard of it.

It is called postoperative cognitive dysfunction, or POCD.

A condition hiding in plain sight

POCD is the sustained cognitive decline some patients experience in the weeks and months following surgery. It is characterized by problems with memory, attention, processing speed, and executive function — the cognitive capacities that make daily life feel familiar and navigable.

The numbers are larger than most people expect:

  • Up to 25–30% of patients over 65 experience POCD after major surgery, depending on the procedure.
  • More than 19 million elderly Americans undergo surgery each year, meaning millions of new cases annually.
  • POCD is associated with longer hospital stays, higher readmission rates, and significant loss of independence in the year after surgery.
  • It is particularly common after cardiac, orthopedic, and abdominal procedures, but it can occur after almost any major surgery.

For a long time, the cognitive symptoms patients reported after surgery were brushed aside as a normal part of recovery — or, worse, as a normal part of aging. They are neither.

Why this has been missed

POCD has been historically underrecognized for a handful of interlocking reasons.

It's hard to measure. Cognitive function is harder to track than blood pressure or pain scores. There is no single, universal test. Symptoms vary in severity and presentation. Many patients don't realize the change is real until weeks after discharge, when they're no longer in regular contact with the surgical team.

It's easy to dismiss. Patients often don't bring it up. When they do, they're frequently told it's stress, age, anesthesia, or "part of recovery." Families assume the same.

It hasn't been treatable. When clinicians have no medication to offer, they have less incentive to formally diagnose. The condition gets absorbed into "the way recovery goes" and is rarely tracked as a complication in its own right.

It's politically uncomfortable. Surgical complications that involve cognition — particularly in elderly patients — sit at an uncomfortable intersection of surgical practice, anesthesia, and geriatric medicine. No single specialty has historically claimed it.

None of these are good reasons to leave the condition where it has been. They are just the reasons it ended up there.

What's actually happening biologically

POCD is no longer a mystery condition. The best-supported explanation involves a process called neuroinflammation — and understanding it is the first step toward treating it.

Surgery is, biologically, a controlled injury. The body responds to it the way it responds to any major insult: with an inflammatory cascade. Signaling molecules called cytokines — among them TNF-α (tumor necrosis factor alpha), IL-1, and IL-6 — surge through the bloodstream to coordinate the body's response.

In a healthy, localized inflammatory response, this is productive. But in the right (or wrong) conditions, some of those cytokines cross the blood-brain barrier — the protective layer that normally keeps the central nervous system insulated from the periphery — and enter the brain.

Once inside, they activate microglia, the brain's resident immune cells. Microglia are not bad actors by default; they protect and maintain the brain's environment. But when they stay activated for too long, they release additional inflammatory signals and disrupt the function of nearby neurons. Memory, attention, and executive function are among the first capacities to suffer.

This mechanism — peripheral inflammation → cytokine crossing → microglial activation → neuronal disruption → cognitive symptoms — is supported by an increasingly strong body of preclinical and clinical evidence. It explains why POCD is more common after long or complex surgeries (more inflammation), in older patients (less robust blood-brain barriers and more baseline neuroinflammation), and in patients with other inflammatory conditions (an already-primed system).

It also points to a clear treatment opportunity: interrupt the cascade, ideally before or around the time of surgery, and you may be able to prevent the cognitive decline that follows.

What patients and families can do right now

There are no approved medications for POCD yet. But there is real work patients and families can do — particularly around recognizing the condition and not allowing it to be dismissed.

Get a baseline. If you or a family member is preparing for a major surgery and is over 65 — or has other risk factors like prior cognitive impairment, vascular disease, or diabetes — consider getting a formal cognitive assessment before the procedure. It establishes a baseline against which any post-operative change can be measured.

Speak up if symptoms persist. Mild cognitive fog in the first week or two after surgery is common. Symptoms that persist beyond a month — or that the patient or family clearly notices as a step down from baseline — warrant a follow-up. Ask for a referral to a neurologist or geriatrician.

Address what's addressable. Sleep, pain control, social engagement, and physical activity all measurably affect cognitive recovery. Treating other inflammatory conditions matters too. None of these are POCD treatments, but each reduces the overall load on the brain during recovery.

Track the symptoms. Keep a simple log. What is the patient forgetting? When? How often? This kind of documentation is the difference between a vague concern and a diagnosable pattern.

What's next in the field

Several research groups around the world are now working on treatments specifically designed to interrupt the neuroinflammatory cascade behind POCD. The most promising approaches share a few characteristics: they target cytokines (particularly TNF-α), they cross the blood-brain barrier so they can act at the site of the cascade, and they are administered around the time of surgery rather than after symptoms appear.

At Nulyn Science, we are advancing NS-001 — a brain-penetrant anti-inflammatory with a long, well-documented safety record — toward a Phase 2 clinical trial in elderly surgical patients. We've submitted our pre-IND package to the FDA, and the trial is scheduled to begin in the second half of 2026.

POCD has been overlooked for decades. That is finally beginning to change.

If you have lived with this — or are caring for someone who has — you are not imagining it, and you are not alone.