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Distal airways dysfunction contributes to respiratory symptoms after World Trade Center dust exposure

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Residents and workers exposed to dust after the 9/11 attack on the World Trade Center (WTC) manifest signs of regional distal airways dysfunction, according to a report in the June 3rd American Journal of Respiratory and Critical Care Medicine.

“Screening spirometry remains normal in the majority of WTC dust exposed subjects despite development of new onset and persistent lower respiratory symptoms,” Dr. Stephen M. Friedman from New York City Department of Health and Mental Hygiene, New York told Reuters Health in an email. “More sensitive measures of airway function may detect abnormalities that are not evident on routine spirometry. Regional distal airways dysfunction may be a contributing mechanism for lower respiratory symptoms in WTC dust exposed subjects.”

Dr. Friedman and colleagues conducted a case-control study of 785 residents and area workers, using data from the WTC Health Registry, to determine whether those with persisting, post-9/11 onset lower respiratory symptoms were more likely than those without such symptoms to have physiologic indicators of airway injury by spirometry and impulse oscillometry (IOS), a more sensitive measure of airway resistance.

One hundred eighty of 274 potential cases reported experiencing a lower respiratory symptom or using an inhaler during the 4 weeks prior to interview and were accepted as cases, and 473 of 511 potential controls reported no such symptoms during the 4 weeks prior to interview and were accepted as controls.

Median percent predicted FEV1 and FVC were significantly lower in cases than in controls, whereas FEV1/FVC did not differ significantly. More cases (18.7%) than controls (11.1%) had abnormal spirometry patterns (P<0.05), and the rates of obstructive and restrictive spirometry patterns were significantly higher for cases than for controls.

Airway resistance measured by IOS was significantly higher in cases than in controls, and significantly more cases than controls had elevated airway resistance, even among those with normal spirometry.

In multivariable analyses, lower respiratory symptoms were significantly associated with IOS results but not with spirometry results.

Other factors significantly associated with case status included dust cloud density, smoke at home or work, dust at home or work, overweight/obese body mass index, black or Hispanic race/ethnicity, female gender, and older age group.

“In smokers, distal airway dysfunction is associated with an accelerated decline in lung function (FEV1),” Dr. Friedman said. “For World Trade Center dust exposed subjects, future longitudinal studies will determine whether our findings progress to overt airflow obstruction. The likelihood of distal airway abnormalities also indicates a potential target for treatment.”

Survivors of 9/11 have also been reported to experience post-traumatic stress disorder and other conditions years after the WTC attack.

“We will soon be conducting the 3rd round of the World Trade Center Health Registry survey with approximately 70,000 current Registry enrollees to obtain updates on their respiratory and other health issues 10 years after 9/11,” Dr. Friedman said. “Approximately 35% of these enrollees resided outside of New York City. Registry enrollees can be found in every state.”

“Our findings demonstrate what can be learned through ongoing study of the health of people exposed to this disaster,” Dr. Friedman concluded. “The continuing cooperation of these enrollees is essential to further understanding of these health effects. Enrollees should remain engaged with the Registry and respond to the Registry’s next health survey which is being launched this month to obtain health updates 10 years after 9/11.”

Am J Respir Crit Care Med 3 June 2011.