TUESDAY, Aug. 4 (HealthDay News) -- People directly exposed to the horrors of the Sept. 11, 2001, attack on the World Trade Center in New York City were reporting new symptoms of post-traumatic stress as long as five and six years after the incident, a new study has found.

In fact, by 2006-2007, more people directly exposed to the event were reporting post-traumatic stress symptoms than in 2003-2004, the study found, and they were about four times more likely than the general population to have such symptoms.

Asthma rates, however, had declined to more or less normal rates by 2007, after being elevated in the months right after the attack, the study reported. The findings are published in the Aug. 5 issue of the Journal of the American Medical Association.

Asthma and symptoms of post-traumatic stress disorder (PTSD) have proven to be the most enduring health consequences of 9/11.

"Five to six years after the event, we found that the vast majority of these people are healthy, but we did find that asthma and PTSD symptoms were elevated," said Lorna Thorpe, senior author of the study and deputy commissioner for epidemiology at the New York City Health Department. "Those elevations were directly correlated with specific 9/11 exposures."

Thousands of people were exposed to the attack, and the World Trade Center Registry was established soon after to follow and document health consequences of the event, especially among rescue workers, residents and passers-by in lower Manhattan at the time.

Of the more than 46,000 people who filled out questionnaires for the latest study, slightly more than 19 percent reported symptoms of post-traumatic stress in 2006-2007, compared with about 14 percent in 2003-2004. None of them had reported such symptoms before 9/11, according to the study.

Groups with the highest levels of chronic post-traumatic stress symptoms were commuters, tourists and other passers-by, with 23 percent reporting symptoms in 2006-2007. Office workers were most likely to have had their symptoms dissipate, and rescue-and-recovery workers were more likely to have developed symptoms later.

"The late onset of post-traumatic stress symptoms is not a surprise but a confirmation that this is a lifetime risk factor," said Dr. Alan Manevitz, a clinical psychiatrist at Lenox Hill Hospital in New York City. He volunteered at the disaster site, working with survivors and family members.

"We would expect that this would have happened," added Keith A. Young, vice chairman for research in the Department of Psychiatry and Behavioral Science at Texas A&M Health Science Center College of Medicine. "It's not strange if symptoms emerge later."

And experts agree that symptoms will often spike as the anniversary of the disaster approaches every year.

Right after the attack, people directly exposed were diagnosed with asthma at six times the rate seen in the general population. By the latest survey, the incidence was down to 10 percent -- much closer to the 7.7 percent asthma incidence found among the general population in a 2007 study.

Firefighters and other rescue-and-recovery workers had the highest rates of new asthma diagnoses, the study found.

"The early incidence of respiratory disease could be directly related to the intensity of the exposure over the first few days," said Jacob Finkelstein, professor of pediatrics, environmental medicine and radiation oncology at the University of Rochester Medical Center. "By the time they got through to 2006, the incidence of respiratory-related symptoms had pretty much declined back to baseline. That's pretty much what you'd expect."

Overall, about 25,500 adults developed asthma after 9/11, and about 61,000 had post-traumatic stress symptoms, the study found.

The two conditions often occurred together.

"There was this interaction between the two," said Dr. Norman Edelman, chief medical officer of the American Lung Association. "And other research indicates that those living in stressful situations seem to be more likely to have asthma."

About 52 percent of those who reported post-traumatic stress symptoms, however, said they had received no treatment in the preceding year.

"As a local health department, we were most concerned and surprised by the increase in PTS symptoms," Thorpe said. "We do know that getting appropriate trauma-specific care is critical so we're making as many efforts a possible to link people to sources of appropriate treatment."

More information

The New York City Department of Health has more on the World Trade Center Registry.

SOURCES: Lorna E. Thorpe, Ph.D., deputy commissioner for epidemiology, Department of Health, New York City; Norman Edelman, M.D., chief medical officer, American Lung Association; Alan Manevitz, M.D., clinical psychiatrist, Lenox Hill Hospital, New York City; Jacob Finkelstein, Ph.D., professor, pediatrics, environmental medicine and radiation oncology, University of Rochester Medical Center, Rochester, N.Y.; Keith A. Young, Ph.D., vice chairman for research, Department of Psychiatry and Behavioral Science, Texas A&M Health Science Center College of Medicine, College Station, Texas; August 5, 2009, Journal of the American Medical Association

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