Cognitive Impairment in 9/11 Responders Tied to Brain Atrophy

Megan Brooks

August 05, 2020

First responders to the World Trade Center (WTC) attacks on September 11, 2001, who have cognitive impairment show cortical thinning across multiple brain regions, including those commonly affected by Alzheimer's disease, suggest results from the first structural neuroimaging study conducted in this population.

The study clarifies that a neurodegenerative condition is present in first responders who experience cognitive impairment in midlife, which "is incredibly important to know," lead author Sean Clouston, PhD, Stony Brook University, Stony Brook, New York, told Medscape Medical News.

The findings were presented at the Alzheimer's Association International Conference (AAIC) 2020, which was held online this year because of the COVID-19 pandemic, and were published online in Alzheimer's and Dementia: Diagnosis, Assessment and Disease Monitoring.

Brain Atrophy in Midlife

During the 9/11 attack and in its aftermath, WTC responders were exposed to a range of inhaled neurotoxicants, as well as extreme psychosocial stressors. A growing number of WTC responders who are now in their 50s and early 60s are experiencing early cognitive impairment.

Using MRI, the investigators examined cortical thickness (CTX), a surrogate marker for neurodegeneration, in 99 mostly male WTC responders; 48 had cognitive impairment, and 51 did not. The age range of the participants was 45 to 65 years, an age range during which cortical atrophy is uncommon in the general population, the researchers note.

Compared with cognitively normal responders, those with cognitive impairment were found to have reductions in CTX across the whole brain and across 21 of 34 cortical regions, including frontal, temporal, and occipital lobes.

In both cognitively impaired and cognitively unimpaired WTC responders, CTX was reduced in the entorhinal and temporal cortices compared with normative data, but reductions were greater with cognitive impairment. Posttraumatic distress disorder (PTSD) status was not predictive of a reduction in CTX across groups.

Clouston said the level of reduction in CTX in many responders is similar to that commonly found in patients with dementia and may reflect early-stage dementia occurring in midlife.

Limitations of the study include the small sample size, the cross-sectional design, the unique nature of the exposure, and a lack of a non-WTC external control group.

"Illuminating" Study

Commenting for Medscape Medical News, Keith Fargo, PhD, director of scientific engagement for the Alzheimer's Association, called the findings "interesting and illuminating" but cautioned that it is not possible to show cause and effect with this type of study.

"We also don't know when cortical thinning might have started or how quickly it might be progressing," Fargo said.

He noted that the pattern of cortical thinning is "somewhat consistent with what we see among people who live with high levels of air pollution, which is an emerging risk factor for Alzheimer's disease and other dementias."

The Lancet Commission on Dementia Prevention, Intervention, and Care added air pollution to its list of modifiable risk factors for dementia, which was recently updated, as reported by Medscape Medical News.

Clinicians "need to be aware that their middle-aged 9/11 first responders are at a higher risk level for cognitive impairment, as well as PTSD and depression," Fargo said.

The study was funded by the Centers for Disease Control and Prevention and the National Institute on Aging. Clouston and Fargo have reported no relevant financial relationships.

Alzheimer's Association International Conference (AAIC) 2020. Presented July 28, 2020.

Alzheimers Dement. Published online July 13, 2020. Full article

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