Source Paper
Mark Farfel, Laura DiGrande, Robert Brackbill, Angela Prann, James Cone et al.
Journal of Urban Health • 2008
To date, health effects of exposure to the September 11, 2001 disaster in New York City have been studied in specific groups, but no studies have estimated its impact across the different exposed populations. This report provides an overview of the World Trade Center Health Registry (WTCHR) enrollees, their exposures, and their respiratory and mental health outcomes 2-3 years post-9/11. Results are extrapolated to the estimated universe of people eligible to enroll in the WTCHR to determine magnitude of impact. Building occupants, persons on the street or in transit in lower Manhattan on 9/11, local residents, rescue and recovery workers/volunteers, and area school children and staff were interviewed and enrolled in the WTCHR between September 2003 and November 2004. A total of 71,437 people enrolled in the WTCHR, for 17.4% coverage of the estimated eligible exposed population (nearly 410,000); 30% were recruited from lists, and 70% were self-identified. Many reported being in the dust cloud from the collapsing WTC Towers (51%), witnessing traumatic events (70%), or sustaining an injury (13%). After 9/11, 67% of adult enrollees reported new or worsening respiratory symptoms, 3% reported newly diagnosed asthma, 16% screened positive for probable posttraumatic stress disorder (PTSD), and 8% for serious psychological distress (SPD). Newly diagnosed asthma was most common among rescue and recovery workers who worked on the debris pile (4.1%). PTSD was higher among those who reported Hispanic ethnicity (30%), household income < $25,000 (31%), or being injured (35%). Using previously published estimates of the total number of exposed people per WTCHR eligibility criteria, we estimate between 3,800 and 12,600 adults experienced newly diagnosed asthma and 34,600-70,200 adults experienced PTSD following the attacks, suggesting extensive adverse health impacts beyond the immediate deaths and injuries from the acute event.
Objective: Evaluation of probable PTSD using the PCL scale and serious psychological distress using the Kessler-6 scale among adults exposed to the 9/11 attacks
Gather these items before starting the experiment. Check off items as you prepare.
SAS Institute • N/A
Chow and Rodgers • N/A
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World Trade Center Health Registry (WTCHR) was created in July 2002 as collaborative effort between ATSDR and NYC DOHMH. Four broad eligibility groups were constructed based on proximity by time and place to WTC attack, acute exposure to dust and debris cloud, and chronic exposure to smoke and fumes.
Note: Estimated total eligible population: 409,492 people
“The WTCHR was created in July 2002 as a collaborative effort between the Agency for Toxic Substances and Disease Registry (ATSDR) and the New York City Department of Health and Mental Hygiene (NYC DOHMH)”
Registrants were recruited through outreach to eligible individuals and groups, local and regional media, and lists provided by employers and governmental agencies. Individuals were contacted via telephone or letter if on provided lists (list-identified), or through widespread advertising campaign encouraging enrollment via toll-free number or website preregistration (self-identified).
Note: 232 lists representing 135,450 potential registrants were provided. Key resource was Port Authority list containing 95,442 names of WTC building security clearance holders.
“Registrants were recruited for enrollment through outreach to eligible individuals and groups, as well as local and regional media. Lists of names and associated contact information of potentially eligible persons were provided voluntarily by entities such as employers and governmental agencies”
Baseline interviews were conducted between September 2003 and November 2004 (2-3 years post-9/11). 67,527 interviews (95%) were completed using CATI and 3,910 using CAPI. Questionnaire was administered in four languages: English (95.2%), Spanish (1.9%), Cantonese (1.5%), and Mandarin (1.0%). Translation service was used for other languages (n=315).
Note: Interviewers took actions (suggested breaks, stopped interview, provided referrals) if respondent showed emotional distress. 3,100 proxy interviews were completed for children under 18 (n=2,635), deceased adults (n=157), and seriously disabled individuals (n=308).
“Of the 71,437 baseline interviews conducted between September 2003 and November 2004 (2–3 years post-9/11), 67,527 (95%) were completed using computer-assisted telephone interviewing (CATI) and the remaining 3,910 were completed using computer-assisted in-person personal interviewing (CAPI)”
Informed consent was obtained from all participants. Eligibility was determined based on the four broad eligibility groups: presence south of Chambers Street on 9/11, WTC site work activities, primary residence south of Canal Street, or school enrollment/employment south of Canal Street.
Note: WTCHR protocol was approved by IRBs of CDC and NYC DOHMH in 2003. Federal Certificate of Confidentiality was obtained.
“The baseline survey was designed to take approximately 30 min to administer. The interview included: (a) informed consent; (b) determination of eligibility”
Demographic information was collected. Contact information for follow-up was obtained, including information on up to three people likely to know future whereabouts of respondent.
Note: N/A
“The interview included: (c) demographics; (d) contact information for follow-up (including information on up to three people who would be likely to know the future whereabouts of the respondent)”
General exposure questions were asked regarding dust and debris cloud exposure. Specific exposure assessment sections were administered for each of the four eligibility groups. Questions assessed being caught in dust cloud, time and location in dust cloud, witnessing potentially traumatizing events, and types of injuries sustained on 9/11.
Note: Specific questions varied by eligibility group (e.g., residents asked about evacuation and return dates, rescue workers asked about work sites and dates)
“The interview included: (e) general exposure questions (e.g., to the dust and debris cloud); (f) specific exposure assessment sections for each of the four eligibility groups; (g) 9/11 injuries”
Participants were asked about physical health outcomes including: injuries sustained on 9/11 (eye injury, fractures, burns, concussions), new or worsening respiratory symptoms after 9/11, new or worsening nonrespiratory symptoms (hearing problems, severe headaches, heartburn, indigestion, reflux, skin rash), and specific conditions diagnosed by healthcare professionals in 2-3 years after 9/11 (asthma, emphysema, hypertension, coronary heart disease, angina, heart attack, diabetes, stroke, cancer).
Note: Questions about symptoms were similar to well-tested examples used in the Behavioral Risk Factor Surveillance System
“Enrollees were asked about physical health outcomes, including: (a) injuries sustained on 9/11 ranging from eye injury or irritation to fractures, burns and concussions; (b) new or worsening respiratory symptoms at any time after 9/11”
The Kessler-6 scale (K-6) was administered to assess serious psychological distress (SPD) in the 30 days prior to interview. Respondents scoring above cutoff of 13 on K-6 scale were classified as having current SPD.
Note: K-6 is correlated with diagnostic measures of major depressive disorder, generalized anxiety disorder, schizophrenia, and other mental disorders
“The Kessler-6 scale (K-6), used to determine SPD, is a psychometrically validated, epidemiologic screening measure used in the National Health Interview Survey since 1997. This paper reports the proportion of respondents who scored above a cutoff of 13 on the K-6 scale to indicate current SPD at the time of the baseline interview”
The PTSD-Checklist Civilian Version (PCL), a 17-item symptom scale corresponding to DSM-IV criteria, was administered to adult participants. Overall prevalence of current probable PTSD was calculated using sum of item responses with cutoff of 44 to classify individuals as likely PTSD cases.
Note: PCL has been validated for use with civilian populations exposed to assault, motor vehicle trauma, and life-threatening or terminal illnesses. Outcome referred to as 'current probable PTSD' to acknowledge that self-reported screening instruments do not necessarily indicate psychopathology.
“The adult interview also included the PTSD-Checklist Civilian Version (PCL), a 17-item symptom scale corresponding to the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, DSM-IV criteria. The overall prevalence of current probable PTSD was calculated using the sum of item responses with a cutoff of 44 which classifies individuals as likely PTSD cases”
Proxy interviews with parents and guardians of child enrollees included an eight-question scale derived from Hoven et al. to assess possible posttraumatic stress symptoms.
Note: Conducted for children under 18 years of age at time of interview (n=2,635)
“Proxy interviews with parents and guardians of child enrollees included an eight-question scale derived from Hoven et al. to assess possible posttraumatic stress symptoms”
For enrollees who reported being caught in dust cloud, geographic location information was collected using street address (n=15,167), closest cross street intersection (n=11,329), closest landmark (n=10,732), or closest subway stop (n=1,119). DCP Geosupport application was used for automated batch matching of street addresses. DCP LION geodatabase was used for geocoding street intersections and manual address matching.
Note: Standard deviational ellipse was constructed centered on mean center of all geocodable locations, with 1 and 2 standard deviational ellipses corresponding to 68.2% and 95.4% of geocoded data respectively
“Enrollees were asked about their geographic location when they first encountered the dust cloud. Locator variables included street address ( n = 15,167), closest cross street intersection (n = 11,329), closest landmark ( n = 10,732), and the closest subway stop ( n = 1,119). Geocoding occurred only if an enrollee answered yes to being caught in the dust cloud”
SAS version 9.1 was used to compute descriptive statistics and bivariate associations between health symptoms or conditions and demographic characteristics, risk factors, and selected event exposures and experiences. Chi-square and Cochran-Armitage tests were used to determine statistical significance.
Note: All enrollees were included in data analysis. Analyses of respiratory and mental health outcomes were restricted to adult enrollees (>18 years) at time of interview, including 157 decedents with limited proxy data.
“SAS ® (version 9.1) was used to compute descriptive statistics and bivariate associations between health symptoms or conditions and demographic characteristics, risk factors, and selected event exposures and experiences. Chi-square and Cochran–Armitage tests were used to determine statistical significance”
Chow and Rodgers' Euler-Venn applet software was used to create a proportional-to-size Venn diagram to depict overlap in eligibility criteria among enrollees.
Note: N/A
“Chow and Rodgers' Euler–Venn applet software was used to create a proportional-to-size Venn diagram to depict overlap in eligibility criteria among enrollees”
To construct estimates of total number of adults eligible for WTCHR who experienced illness or symptoms after attacks, prevalence of self-reported health problems among enrollees was applied to estimates of total number of persons exposed for each enrollee category. All exposed adults were categorized into three mutually exclusive hierarchical categories: rescue and recovery workers/volunteers, building occupants/passersby/people in transit, and residents south of Canal Street.
Note: Three estimates were calculated: midpoint estimate (assuming ill persons more likely to self-enroll), upper bound estimate (assuming self-identified prevalence representative of entire population), and lower bound estimate (assuming 50% higher enrollment among symptomatic list-identified persons). Estimates rounded to nearest hundred.
“To construct estimates of the total number of adults eligible for the WTCHR who experienced illness or symptoms after the attacks, the prevalence of self-reported health problems among enrollees was applied to estimates of the total number of persons exposed for each enrollee category”
Individuals exposed to 9/11 attacks in New York City; 67,527 completed CATI interviews, 3,910 completed CAPI interviews, 3,100 proxy interviews