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 age 65.
Study: Incidence of dementia before age 65 among responders to the World Trade Center attacks. Image credit: Anthony Correia / Shutterstock.com
The chronic health effects of 9/11
The collapse of the WTC Twin Towers on September 11, 2001, resulted in the release of a huge cloud of dust, debris, and numerous toxic substances that spread over most of lower Manhattan and other parts of New York City.
First responders, residents and workers in this area experienced many immediate health effects after exposure to these toxins, some of which included respiratory problems, eye and skin irritation, and worsening of pre-existing conditions such as asthma. Long-term exposure has also been associated with many chronic respiratory diseases, cancers and other diseases.
More recently, researchers reported that WTC first responders who reported heavy exposure to dust and particulate matter have cognitive dysfunction, cognitive decline, and extensive brain atrophy, which are risk factors for dementia in middle age. Compared to the average population, the incidence of dementia in people before the age of 65 is relatively low at 1.19 cases for every 1,000 person-years (PY).
What did the findings show?
The researchers of the current study assessed cognitive and functional limitations in 5,010 general WTC responders. The median age of the study cohort was 53 years at baseline, of which 8.7% were female and 91.3% were male. Over 87% of the study cohort was White, while 3.1%, 2.8%, and 6.8% were Black, Hispanic, or other race and ethnicity, respectively.
The study period extended from November 1, 2014 to January 1, 2023. Follow-up to detect the onset of dementia was conducted for an average of 18 months among people aged 60 years or younger for a maximum of five years.
All study participants worked or volunteered at the WTC site for four or more hours between September 11, 2001 and September 14, 2001, for 24 hours at any 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, to smoke, and to have completed some level of college education, and less likely to have diabetes, compared with other eligible participants who declined cognitive assessments.
Exposure to fine particulate matter (FPM) or debris containing chemicals that could potentially damage brain tissue was assessed in graded categories. The duration of work at the site and the use of personal protective equipment (PPE) were also recorded.
Overall, the incidence of dementia before age 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 subjects with low, mild, moderate, high, and severe exposure, respectively.
When stratified by dust exposure, the risk of dementia increased tenfold among those with severe dust exposure compared with those who used PPE or were not exposed. This increase persisted despite consideration of confounders such as hypertension or head injuries, post-event psychiatric illness, social characteristics, and demographic factors.
After full adjustment for confounders, the incidence of dementia increased by 40% with each unit increase in exposure severity.
conclusions
Compared to lower levels of exposure or PPE use, severe exposure to dust and potentially hazardous debris after the collapse of the Twin Towers was associated with a significantly greater risk of dementia before age 65. Importantly, this association remained significant after adjustment for potential confounders such as education level, psychiatric sequelae, as well as the presence of comorbidities such as hypertension and chronic or severe head injuries.
These findings confirm previous rodent studies suggesting that WTC dust exposure leads to altered olfaction, working memory, visuospatial learning, and behavior. Similarly, neuroimaging studies in WTC responders have identified glial activation and hippocampal inflammation. However, 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 may help prevent dementia onset before age 65 in people exposed to uncontrolled building collapse.’
Journal Reference:
- Clouston, SAP, Mann, FD, Meliker, J., et al. (2024). Incidence of dementia before age 65 among responders to the World Trade Center attacks. JAMA Network Open. doi:10.1001/jamanetworkopen.2024.16504.
