People involved in rescue and recovery after the World Trade Center (WTC) attacks on September 11, 2001, are less likely to have died than members of the general population of New York City (NY, USA), according to a new study.

Researchers at the New York City Department of Health and Mental Hygiene (NY, USA) conducted an observational cohort analysis, examining deaths during 2003-2009 among participants of the WTC Health Registry; 71,437 people completed interviews for the registry during 2001-2003 that recorded demographics, exposures incurred during and after the event, and health information. All told, the analysis included 13,337 people involved in rescue and recovery and 28,593 residents, workers, school staff and students, commuters, and passers-by who were present during the events.

The researchers found 156 deaths among the 13,337 rescue and recovery workers, and 634 deaths in the remaining 28,593 members of the cohort. The standardized mortality ratio for all causes of death was significantly lower than expected for those involved in rescue and recovery; the same was true for nonrescue/nonrecovery participants, but no standardized mortality ratios were increased significantly for a range of heart diseases or for hematological malignancies. In nonrescue/nonrecovery participants--but not in the other participants-- intermediate and high exposures were significantly associated with mortality, and high exposure was associated with heart disease-related mortality, when compared to low exposure. The study was published in the September 3, 2011, issue of the Lancet.

“The findings are not surprising, since most illnesses that are either established or possible results of the 9/11 events have either long latency or long median survival periods,” concluded lead author Hannah Jordan, MD, and colleagues. “Two other factors might also play a role; first is the so-called healthy worker effect--most of the participants were employed, and employed people in general are healthier than the overall population. Second, people who offer to participate in health studies tend to be healthier than the general population, a healthy volunteer effect.”

The September 11 attacks were a series of four coordinated attacks against the United States on Tuesday, September 11, 2001. On that morning, 19 al-Qaeda terrorists hijacked four passenger jets. The hijackers intentionally crashed two planes into the Twin Towers of the WTC in New York City, and both towers collapsed within two hours. Hijackers crashed a third plane into the Pentagon in Arlington (VA, USA). When passengers attempted to take control of the fourth plane, United Airlines Flight 93, it crashed into a field near Shanksville (PA, USA), preventing it from reaching its intended target in Washington DC (USA). Nearly 3,000 people died in the attacks.

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