Health impacts from 2001 U.S. attacks linger: study

CHICAGO (Reuters) - The September 11, 2001 attacks that brought down New York's World Trade Center continue to trigger health problems for tens of thousands of people exposed to the horrors and dust of that day, researchers said on Tuesday.

More than 400,000 office workers, residents, rescuers and passersby were in lower Manhattan on September 11 or shortly afterward, and an estimated 25,000 have since developed asthma and 61,000 suffer from post-traumatic stress, they reported in the Journal of the American Medical Association.

The hijacked plane attacks that collapsed the twin towers killed nearly 3,000 people.

"The diagnoses correlated with the exposures people had," such as witnessing people jumping from the burning towers or direct contact with the dense, billowing dust cloud following the towers' collapse, said Lorna Thorpe, a deputy commissioner for the New York City Health Department.

Thorpe and colleagues from Columbia University and the U.S. Centers for Disease Control and Prevention used two surveys performed in 2003-2004 and 2006-2007. The work is part of The World Trade Center Health Registry, the largest post-disaster exposure registry in U.S. history.

Ten percent reported newly diagnosed asthma afterward, they found.

What was surprising to Thorpe and fellow researchers was that new cases of post-traumatic stress disorder or PTSD increased over time.

"We had more people symptomatic in the second survey than we anticipated. Some people resolved (their symptoms), but for an even larger number of people their symptoms worsened," she said in a telephone interview.

In the initial survey, 14 percent experienced PTSD symptoms, which faded for about one-third of them. But another 10 percent of more than 46,000 survey respondents reported symptoms in the second survey, she said.

PTSD symptoms include flashbacks, nightmares, depression and feelings of avoidance and detachment.

Thorpe said subsequent job losses or other traumas were factors in triggering late-onset symptoms in those with direct experience of the September 11 hijack plane attacks.

Twenty-one percent of participants reported having seen a mental health professional in the past year, and 14 percent reported taking medication for a mental health condition.

"We're looking very carefully at the late-onset group, the resolved group, and the resilient group to understand them better," Thorpe said.

The resilient group were the 76 percent of respondents who reported no noticeable post-traumatic stress symptoms.

In contrast, new cases of asthma that reached 14 percent of respondents within a few months of the attacks gradually declined to more normal levels.

(Editing by Maggie Fox and Eric Walsh)