14 Jun 2024

In the decades after the World Trade Center collapse, people who cleaned up the rubble have developed post-traumatic stress disorder, lung problems, cancer, and cognitive impairment. They also seem to be at high risk for early onset dementia, say scientists led by Sean Clouston at Stony Brook University in Long Island and Benjamin Luft of the World Trade Center Health Program in Commack, both in New York. In the June 12 JAMA Network Open, they reported that responders exposed to the most toxic dust were 9.5 times more likely to develop early onset, all-cause dementia than those who breathed little dust or wore personal protective equipment. This study supports the idea that pollution exposure drives cognitive problems in WTC responders and indicates that PPE could protect people exposed to dust from collapsed buildings.

“This is an excellent next step in a series of observations and analyses on WTC responders,” Caleb (Tuck) Finch, University of Southern California, Los Angeles, told Alzforum, though he noted this may be unrelated to typical air pollution. “The WTC collapse was a unique event generating high levels of toxic components from building materials that are different from chronic traffic-related air pollution to which the general population is exposed.”

Four years ago, Clouston published evidence of cognitive impairment in some WTC responders in their 50s, linking it to their PTSD and toxic dust exposure (Jan 2020 news; Clouston et al., 2019). Now, he has updated data to include early onset dementia risk.

For the current study, first author Clouston and colleagues analyzed clinical data from 5,010 WTC responders, almost all Caucasian men. Beginning in 2014, when they were 53 years old, on average, each completed the Montreal Cognitive Assessment every 18 months for five years. The scientists measured the incidence of all-cause dementia before age 65, determined as episodic memory and executive function scores on the MoCA two standard deviations below the cohort mean, and evidence of functional limitations, such as trouble recognizing common shapes, orienting common objects, or doing simple calculations. They did not measure any plasma or CSF biomarkers to distinguish specific types of dementia.

To correlate dementia incidence with risk, Coulson had the responders answer a questionnaire in 2002 about their exposures at the WTC site, including duration and type of work, use of personal protective equipment (PPE) such as respirators and hooded Hazmat suits, and exposure to fine particulate dust, a type of pollution known to be neurotoxic (Aug 2020 news; Dec 2020 news; Kritikos et al., 2020). He split exposure levels into five categories, from low to severe. The latter included sifting through building debris, working in dusty or enclosed areas, and being exposed to chemicals, fumes, or smoke without using PPE. Low exposure included routinely wearing PPE or working in areas with little to no dust or in clean rooms. Eighty-five percent of the responders had mild to moderate exposure.

Toxic Dust. First responder wearing an N95 face mask at the WTC site. 

Between 2014 and 2019, 228 responders were diagnosed with dementia. Incidence increased with age and stepwise with exposure to toxic dust (image below). It rose from 2.95 cases per 1,000 person-years in people with low exposure to a whopping 42.37 cases with severe exposure. Incidence in the general population is about 1.19 early onset dementia cases per 1,000 person-years (Jul 2021 news). In other words, responders with severe or high exposure were 9.5 and 8.5 times likelier to develop early onset dementia than those with low exposure. These hazard ratios were calculated after adjusting for demographic, lifestyle, and health factors, including sex, years of education, smoking history, drinking habits, and diagnosis of diabetes, high blood pressure, or heart disease.

Worse Exposure, Higher Risk. WTC responders with the most exposure to toxic dust were the likeliest to develop early onset, all-cause dementia. Risk decreased incrementally with less exposure. [Courtesy of Clouston et al., JAMA Network Open, 2024.]

Clouston previously found that cognitive impairment correlated with a person’s PTSD symptoms, leading some scientists to believe poor cognition might be secondary to that trauma. While the current study did not look at PTSD and dementia risk, the dose response backs up the idea that pollution contributes to dementia.

This is the first study to link exposure to toxic dust from the WTC site with dementia. It also highlights the importance of wearing PPE. “There is a critical need to protect persons who help in rescue and recovery operations after an unexpected industrial accident,” the authors wrote.” Earthquakes and other natural and man-made disasters could pose similar risk.—Chelsea Weidman Burke

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References

News Citations

1. Do World Trade Center Responders Get Early Onset Plaques and Tangles? 28 Jan 2020
2. Lancet Commission’s Dementia Hit List Adds Alcohol, Pollution, TBI 4 Aug 2020
3. You Are What You Breathe: Polluted Air Tied to Plaques, Brain Atrophy 10 Dec 2020
4. Estimates of Young-Onset Dementia Prevalence Just Doubled 22 Jul 2021

Paper Citations

1. Clouston SA, Diminich ED, Kotov R, Pietrzak RH, Richards M, Spiro A 3rd, Deri Y, Carr M, Yang X, Gandy S, Sano M, Bromet EJ, Luft BJ. Incidence of mild cognitive impairment in World Trade Center responders: Long-term consequences of re-experiencing the events on 9/11/2001. Alzheimers Dement (Amst). 2019 Dec;11:628-636. Epub 2019 Sep 6 PubMed.
2. Kritikos M, Gandy SE, Meliker JR, Luft BJ, Clouston SA. Acute versus Chronic Exposures to Inhaled Particulate Matter and Neurocognitive Dysfunction: Pathways to Alzheimer's Disease or a Related Dementia. J Alzheimers Dis. 2020;78(3):871-886. PubMed.

Further Reading

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