Why 9/11 first responders see higher rates of dementia

First responders with the highest (vs the lowest) exposure to the dust and potentially neurotoxic debris during the terrorist attacks on the World Trade Center (WTC) site on September 11, 2001, were over 14 times more likely to be diagnosed with dementia before the age of 65. This is according to a study of more than 5,000 first responders who underwent long-term regular testing. The findings were published in JAMA Network Open.^[]

 “We focused on dust in this study because that is what people could see,” explained co-author Sean Clouston, PhD, in speaking to The Washington Post.^[] “They knew if they had or had not been exposed to it."

Longitudinal follow-up study

A prior study by Dr. Clouston and colleagues found that the longer the time first responders spent at the WTC site, the more inflammation they had in their hippocampus—which plays a crucial role in memory—and cerebral white matter.^[] In the latest study, the researchers compared the incidence of all-cause dementia before age 65 years in two groups of 9/11 responders: those with severe building debris exposure and those not exposed to debris or who wore personalized protective equipment (PPE).

The prospective study ran from November 2014 to January 2023. It included 5,010 WTC responders (median age, 53; male, 91.3%) without dementia who lived in Long Island, NY, and were participating in an academic medical monitoring program for verified WTC responders. Participants completed a questionnaire covering their exposure to fine particulate dust and potentially neurotoxic debris, as well as their duration of work and PPE use. Researchers divided the level of debris exposure into five categories: low, mild, moderate, high, and severe. 

For the low, mild, moderate, high, and severe exposure levels, the respective incidence rates of developing dementia before the age of 65 stood at 2.95, 12.16, 16.53, 30.09, and 24.37 per 1,000 person-years.

The authors concluded that “the reliable use of PPE might help prevent the onset of dementia before age 65 years among individuals exposed to an uncontrolled building collapse." In addition, they wrote, “Future research is warranted to determine cerebral biomarkers for individuals with exposure-associated dementia.”

Dementia and air pollution

An NIH-funded study included data from 27,000 adults with an average age of 60, of whom 15% developed dementia. The researchers found a link between a higher exposure to fine particulate matter and an increased dementia risk. Participants who developed dementia were more likely non-White, less educated, poorer, and residing in locations with higher fine particulate matter levels.

“The strongest links between pollution and dementia were seen for [fine particulate matter] from agriculture and wildfires,” the NIH reported. 

Meanwhile, a 2022 report from the UK Government found that air pollution likely contributes to dementia in older people.^[] The Committee on the Medical Effects of Air Pollutants reviewed 69 epidemiological studies that assessed the potential link between air pollutants and dementia. 

A more plausible mechanism is that small-particle air pollution causes damage to the brain's blood vessels, linking it, thereby, to vascular dementia. “Therefore, we think it likely that air pollution contributes to mental decline and dementia caused by effects on the blood vessels,” the authors wrote.

Exposure-reduction measures

Individuals with heart disease, lung disease, or diabetes, along with older adults and individuals younger than 18 years, are most likely to be adversely affected by particle pollution exposure.

“In your patient education,” the EPA suggests, “you should encourage awareness of daily air quality, which can be found in weather broadcasts, on websites, or through the use of notifications that provide it via email, or an app (airnow.gov has forecasts as well as links to the email notification and app).” The agency recommends that healthcare providers give advice to reduce exposure by “basing activity on the air quality and on the patient’s level of risk.”