9/11 first responders face increased midlife dementia risk from severe dust exposure

By Dr. Liji Thomas, MDReviewed by Benedette Cuffari, M.Sc.Jun 17 2024

A recent study published in JAMA Network Open reveals that severe dust exposure among a subset of World Trade Center (WTC) responders is associated with higher rates of dementia before the age of 65 years.

Study: Incidence of dementia before age 65 years among World Trade Center attack responders. Image Credit: Anthony Correia / Shutterstock.com

The chronic health effects of 9/11

The collapse of the Twin Towers of the WTC on September 11, 2001, led to the release of an enormous cloud of dust, debris, and numerous toxic substances that spread throughout most of lower Manhattan and other parts of New York City.

First responders, residents, and workers in this area experienced many immediate health effects following exposure to these toxins, some of which included respiratory issues, eye and skin irritation, as well as worsening of pre-existing conditions like asthma. Long-term exposure has also been associated with several chronic respiratory diseases, cancers, and other diseases.

More recently, researchers have reported that WTC first responders who reported heavy exposure to dust and particulate matter experience cognitive dysfunction, cognitive decline, and widespread cerebral atrophy, all of which are risk factors for dementia at midlife. As compared to the average population, the incidence of dementia in individuals before 65 years of age is relatively low at 1.19 cases for every 1,000 person-years (PY).

What did the findings show?

The current study's researchers assessed cognition and functional limitations in 5,010 WTC general responders. The median age of the study cohort was 53 years at baseline, 8.7% of whom were female and 91.3% were male. Over 87% of the study cohort were White, whereas 3.1%, 2.8%, and 6.8% were Black, Hispanic, or another race and ethnicity, respectively.

The study period extended from November 1, 2014, to January 1, 2023. Follow-up to detect dementia onset was conducted on an average of 18 months among individuals 60 years or younger for a maximum of five years.

All study participants worked or volunteered in the vicinity of the WTC for four or more hours between September 11, 2001, and September 14, 2001, for 24 hours at any time other time in September of that year, or for at least 80 hours between September 11, 2001, and July 31, 2002. Study participants were more likely to be older, smoke, and complete some level of university education, as well as less likely to have diabetes, as compared to other eligible responders who refused cognitive assessments.

Exposure to fine particulate matter (FPM) or debris containing chemicals that could possibly damage brain tissue was assessed in graded categories. The duration of work at the site and use of personal protective equipment (PPE) was also recorded.

Overall, the incidence of dementia before the age of 65 was 14.5 for every 1,000 PY. The incidence of dementia was 2.95, 12.2, 16.5, 30.1, and 42.4 for every 1,000 PY among individuals with low, mild, moderate, high, and severe exposure, respectively.

When stratified by dust exposure, dementia risk increased tenfold among those with severe dust exposure compared to those who used PPE or were not exposed. This increase persisted despite considering confounding factors, including hypertension or head injuries, post-event psychiatric illness, social characteristics, and demographic factors.

After full adjustment for confounding factors, the incidence of dementia rose by 40% with each unit of increase in severity of exposure.

Conclusions

As compared to the lowest exposure levels or use of PPE, severe exposure to dust and potentially dangerous debris following the collapse of the Twin Towers was associated with a significantly greater risk of dementia before the age of 65 years. Importantly, this association remained significant after adjusting for potentially confounding factors such as education level, psychiatric sequelae, as well as the presence of co-morbidities like hypertension and chronic or severe head injuries.

These findings corroborate previous rodent studies suggesting that WTC dust exposure leads to altered olfaction, working memory, visuospatial learning, and behavior. Likewise, neuroimaging studies in WTC responders have identified glial activation and hippocampal inflammation. Nevertheless, additional research is needed to elucidate the mechanisms that may be responsible for the increased risk of cognitive impairment in WTC responders and other individuals exposed to these neurotoxicants.

Reliable use of PPE might help prevent the onset of dementia before age 65 years among individuals exposed to an uncontrolled building collapse.’