As we approach the 10th anniversary of 9/11, The Lancet published 3 studies on the health of people at the World Trade Center site on 9/11. We should pause and remember that while civilians were trying to escape, members of the FDNY and other first responders ran towards the danger. That’s what they do – run into burning buildings. Heroes.
Our mission at TIE is research-based health policy. The key issues in these Lancet studies are the control groups and surveillance bias. We rely on research, even for heroes.
The first study reports all-cause mortality for the 41,930 people enrolled in the World Trade Center Health Registry cohort (2003-2009 data; Jordan HT et al.) The surprising findings include a much lower standardized mortality ratio (SMR):
All-cause SMRs were significantly lower than that expected for rescue and recovery participants (SMR 0·45, 95% CI 0·38—0·53) and non-rescue and non-recovery participants (0·61, 0·56—0·66). No significantly increased SMRs for diseases of the respiratory system or heart, or for haematological malignancies were found.
You read that right: 9/11 workers are dying at a 55% lower rate and are not dying at a higher rate from heart/lung diseases or cancer. The differences are huge – any drug with this effect on mortality over 10 years would be worth >$100 billion. Note that 10 years might not be long enough for some long-latency diseases to impact SMR.
The chronic disease study (by Wisnevsky JP et al.), tracked 27,449 participants in the WTC Screening, Monitoring, and Treatment Program, and found a substantial burden of physical and mental chronic diseases, including asthma, sinusitis, GI disease, depression, PTSD and panic disorder:
We reported that about 10–30% of rescue and recovery workers still had persistent medical disorders 9 years after the WTC attacks. More than a fifth had multiple physical and mental health problems. Most health disorders were more common in rescue and recovery workers with highest levels of exposure to dust and smoke than in those with lower levels of exposure.
This study did not use an external control group, noting problems with finding a control group that was as healthy as the study population. The study found significant dose-response, but does not tell us whether the rescue and recovery workers are sicker (or how much sicker) than any other group of Americans.
The final study, the FDNY cancer study got the most press, by far. This study (by Zeig-Owens R et al.) found a 10% increase in cancer incidence (not mortality) in the 8927 WTC-exposed FDNY fire fighters, compared to the US population.
But these fire fighters don’t have normal American health care, they are perhaps the best-screened population in history, due to the various funds established to care for 9/11 first responders. Correction for this surveillance bias is important, because 30 of the increased cancers in the exposed group were prostate cancer (observed 90, expected 60), which may be due to better screening rather than 9/11-related etiology. You might expect lung cancer to be the WTC leader, but lung cancers were actually much lower than expected: (observed 9, expected 21). The causal story is unclear at this point. After correcting for surveillance bias, the net increase in FDNY cancers compared to the general population? 4 cancers, SIR of 1.02 (2% increase) with a 95% CI of 0.90 – 1.15:
Higher rates of cancer were found when the control group was shifted to the FDNY members who didn’t go to the WTC (1.32 without correction for surveillance bias, 1.21 above after correction, 1.19 after full lagging), mainly because this control group had a much lower cancer incidence than expected (perhaps fire fighters are in better shape and smoke less than average). 19% higher incidence rate = perhaps 39 38 additional cancers out of 8927 exposed FDNY members. The choice of control group makes a huge difference. Remember also that this cohort does not have higher cancer mortality at this time (first study), perhaps due to increased surveillance, medical attention and long latencies.
Tomorrow I’ll post my media score card on how these studies were reported. On Thursday, the NIOSH decision to not include cancer in the Zadroga fund.
