Hundreds of first responders have told me they remember exactly how they felt during the World Trade Center attacks, even 25 years on.
They tell me that they remember not being able to think, see or smell anything. They could focus only on digging and pulling debris out of the way.
They could not rest because those trapped beneath the rubble could not wait. Death was all around them, and they could only do as much as they could to hold it back.
While what happened on 9/11 was unprecedented, similar tragedies happen quite frequently.
As a physician in occupational health who works with 9/11 first responders, I can easily imagine those same thoughts from other firefighters, paramedics and construction workers trying to save lives after the deadly summer 2026 earthquakes in Venezuela, Colombia and Indonesia or the disastrous floods in Nepal.
These first responders may also need to recover human remains from the rubble. Surrounding these moments of intimate grief are dust, toxic fumes and cries for help. And this trauma takes a toll.
Whether it’s industrial or nuclear disasters, extreme weather, wildfires, volcanic eruptions, war or terrorist attacks, first responders and affected communities can experience significant physical and mental health effects both during rescue and recovery operations and for years afterward.
All are vulnerable to mental and physical harm no matter how well trained they may be.
Research from my team suggests that among these risks is post-traumatic stress disorder that may cause their brain to age faster.
People gather by a reflecting pool during a memorial on the 25th anniversary of the 9/11 terrorist attacks on September 11, 2026
Nearly 3,000 people died in the 9/11 terror attacks in 2001
PTSD among first responders
Post-traumatic stress disorder, also known as PTSD, is a complex mental health condition that can develop after experiencing or witnessing a traumatic event.
Psychological trauma refers to the lasting emotional effects of direct or indirect exposure to life-threatening circumstances or violence.
PTSD may involve intrusive memories, avoidance, heightened alertness, sleep problems and changes in mood and thinking. Anxiety and depression commonly occur alongside PTSD.
Around 23 percent of World Trade Center responders have been diagnosed with PTSD. In comparison, around six percent of the US general population are estimated to have had PTSD over their lifetime.
When I talk to 9/11 first responders, they describe their PTSD and cognitive difficulties as interconnected problems that continue to affect their lives today.
Those traumatic memories remain vivid, and some first responders continue to experience anxiety, depression, intrusive thoughts, sleep problems and difficulty controlling their emotions.
Trauma speeds brain aging
As they age, many 9/11 first responders have also noticed their memory, concentration and mental sharpness get worse.
They increasingly fear losing their independence. Rather than occurring as separate conditions, physical illness, cognitive changes and emotional distress often reinforce one another.
In another study, researchers from my team monitored the cognitive function of more than 5,000 World Trade Center first responders without dementia between 2014 and 2022.
Firemen make their way through the rubble and debris after the collapse of one of the towers on September 11, 2001
Over approximately five years, 228 developed dementia before age 65.
First responders with the most severe exposure to potentially neurotoxic dust and debris at ground zero had a substantially higher incidence of dementia than those with minimal exposure or who consistently used personal protective equipment such as respirators.
This link remained after controlling for demographic, lifestyle, medical and genetic factors.
Before I began studying the health effects of 9/11, I was examining workers exposed to neurotoxic metals and industrial pollution in northern Italy.
Knowing the harmful toxins in World Trade Center dust, I began to wonder whether 9/11 responders might face similar long-term risks to their brains.
That concern grew when brain scans of both groups showed a similar increase in deposits of a protein linked to Alzheimer’s disease and cognitive decline called beta-amyloid.
Research from my team also found that the brains of 9/11 male responders with PTSD had MRI results consistent with older-appearing brains than those without PTSD.
In that 2025 study, we measured the brain structures using MRI scans and an AI model to estimate each participant’s brain age.
The AI model had been trained to predict a person’s chronological age from the overall structure of their brain, based on data from more than 11,500 MRI brain scans from healthy people ages 5 to 95.
We used the difference between a person’s predicted brain age and their actual age as a measure of accelerated brain aging.
We also saw that first responders with PTSD had brains that appeared about three years older than their chronological age.
In contrast, the estimated brain age of responders without PTSD approximately matched their actual chronological age.
Each additional month a first responder spent working at ground zero was associated with roughly four to five additional months of apparent brain aging, suggesting that how long they were exposed to the disaster played a key role in this aging process.
A fireman rests near the destroyed World Trade Center on September 12, 2001 in New York
An ambulance, covered with debris, is on fire after the collapse of the first World Trade Center Tower on September 11, 2001
Caring for first responders
The experiences of first responders show that the effects of 9/11 are an ongoing health issue. These health consequences evolve as people age, and they still require coordinated mental, cognitive, physical and social support decades later.
Every 9/11 anniversary brings back vivid memories of the tragedy, along with the same restlessness, frustration and pain of being there.
Yet many on the front lines have told me that they feel pride and a sense of belonging with the knowledge that they helped people in desperate need. Their service remains an enduring example of human solidarity in a moment of crisis.
Honoring that legacy means protecting those who come to our rescue during an emergency.
This article is adapted from The Conversation, a nonprofit news organization dedicated to sharing the knowledge of experts. It was written by Roberto Lucchini, a professor of Occupational and Environmental Health Sciences at Florida International University. It was edited by Alexa Lardieri, Daily Mail’s US health editor.