A new study based on eleven years of post-World Trade Center (WTC) follow-up found that persons who experienced an injury during or immediately after the collapse of the towers on the morning of 9/11 had an increased risk of subsequent heart disease, and that acute exposure to the dust cloud that morning was associated with increased asthma and other lung diseases.

The findings are published online in the journal Injury Epidemiology.

[Photo: Dr. Steven Stellman]

This is among the first studies to focus on acute injuries and other exposures that occurred on the morning of 9/11 and chronic exposures in homes and workplaces during the extensive clean-up period to the exclusion of continuous exposure to workplace and household dust before and during the lengthy cleanup process. Disease occurrence was monitored for up to 11 years after 9/11, making this study also one of the longest 9/11 study periods to date.

“Most studies of World Trade Center survivors have been limited to physical and mental health problems that developed during the first few years following the attacks,” said Dr. Steven Stellman, a co-author on the paper, professor of epidemiology at Columbia University’s Mailman School of Public Health and former research director of the World Trade Center Registry. “Our study fills an important gap in our knowledge, strongly suggesting that the injury itself may be a precursor of later illness, although a possible mechanism has yet to be identified.”

Dr. Stellman and co-authors from the New York City Department of Health and Mental Hygiene based their analysis on data from 71,431 men, women, and children who were first interviewed in 2003-2004, and who also answered health questionnaires in 2006-2007 and 2011-2012. People with many types of both short-term and long-term exposures were studied as were those with injuries experienced directly on 9/11, rescue and recovery workers who were at the 9/11 site on the day of the attack, and residents, workers, and passersby who were also downtown at the time. Excluded were people age 65 and older who already may have had  existing chronic illnesses. In the final analysis, there were 8,701 people studied, of whom 249 were rescue and recovery workers, 131 were local residents, and 818 were passersby. The researchers also calculated the risk of developing an illness among exposed persons relative to unexposed persons.

Other key points that distinguish this study from previous 9/11 studies:

• Rescue and recovery workers who arrived later in the week, local residents who did NOT evacuate their homes immediately, and area workers who returned immediately afterwards were excluded from the study, since all of these people would have experienced chronic exposures.
• Each study participant reported whether he or she had experienced each of five different types of injury (cut, fracture, sprain/strain, burn, or concussion). The affected part of the body was not recorded.
• Three disease endpoints were studied: heart disease, asthma and other lung diseases, and diabetes.
• Chronic diseases generally affect older people, and require a lengthy follow-up. In this study disease occurrence was monitored for up to 11 years after 9/11, making this one of the longest 9/11 study periods to date.
• The number of injury types was strongly associated with heart disease, with two injuries tripling the risk relative to no injuries
• A 30 percent increase in the risk of asthma and other non-cancer lung diseases was associated with 9/11 injury.
• Diabetes was not related to injury.

The investigators counsel that “continued monitoring of 9/11 exposed persons’ health by medical providers is warranted for the foreseeable future.”

The study was supported by the National Institute for Occupational Safety and Health, CDC (2U50/OH009739 and 5U50/OH009739); Agency for Toxic Substances and Disease Registry, and the National Center for Environmental Health, CDC (U50/ATU272750); and the New York City Department of Health and Mental Hygiene.