Selection bias may lead to underestimation of risk of CTE in former
football players
New statistical methods to prove that dose-response relationship cannot
be due to sampling bias
Date:
April 28, 2022
Source:
Boston University School of Medicine
Summary:
Researchers have been studying chronic traumatic encephalopathy
(CTE) and while much has been learned, diagnosing the disease still
needs to be done post-mortem on autopsied brains donated to a brain
bank. One criticism of the research is that brain bank study results
have a selection bias because they are based on a subset of players
most affected by CTE, and therefore not representative of the
population of football players. Now a novel study by researchers
from BUSM and Boston University School of Public Health (BUSPH)
provides further evidence suggesting a dose-response relationship
between football and CTE even after adjusting for selection bias.
FULL STORY ========================================================================== Since 2008, Boston University School of Medicine (BUSM) researchers
have been studying chronic traumatic encephalopathy (CTE) and while
much has been learned, diagnosing the disease still needs to be done post-mortem on autopsied brains donated to a brain bank. One criticism
of the research is that brain bank study results have a selection bias
because they are based on a subset of players most affected by CTE,
and therefore not representative of the population of football players.
==========================================================================
Now a novel study by researchers from BUSM and Boston University
School of Public Health (BUSPH) provides further evidence suggesting a dose-response relationship between football and CTE even after adjusting
for selection bias.
CTE is a progressive brain disease associated with repetitive head
impacts. It has been diagnosed after death in American football players
and other contact sport athletes as well as members of the armed services
and victims of physical abuse.
"The validity of research involving CTE has been questioned due to the
inherent bias in the selection process of brain donation studies. A prior
BUSM study that identified a strong dose-response relationship between
years of football played and likelihood of developing CTE, which supports
a cause-effect relationship between repeated head impacts and CTE, has
been ignored by some sports organizations due to claims of selection
bias. To respond to such criticism, there is a significant need to adjust
for it in the analytical phases of these studies," explains corresponding author Yorghos Tripodis, PhD, professor of biostatistics at BUSPH.
Utilizing data from Veterans Affairs-Boston University-Concussion Legacy Foundation (VA-BU-CLF) Brain Bank, the researchers undertook a new
study to analyze 290 male former football players to further clarify
the dose-response relationship. After developing multiple statistical
models to adjust for selection bias, college and professional football
players respectively were found to have a 2.38 and 2.47 times higher
risk of being diagnosed with CTE relative to high school players.
"Strikingly, these risk ratios were actually heightened after accounting
for selection bias. This is in stark comparison to the previous critiques received as it suggests that prior data may actually underestimate risk
of CTE in these populations," said Tripodis.
The researchers also calculated the minimum cumulative incidence of CTE
for different levels of play. They found the minimum possible cumulative incidence for professional players is one in 10, one in 250 for college football players, and 1 in 20,000 for high school players. However,
they anticipate future studies will reveal the actual risk is many times
higher for each level of play.
The authors end by prompting the need for further investigation into
the type of participants that are under-represented in the brain bank
leading to this selection bias and the need for additional recruitment
efforts targeted at these populations to allow for additional study.
"Our new study provides further evidence to support a dose-response relationship between playing football and developing CTE. We hope the
football community will accelerate reforms aimed at preventing CTE
by limiting head impacts for players and that parents will use this
information to make more informed choices about sports participation
for their children," he adds.
These findings appear online in the American Journal of Epidemiology.
Funding for this research was provided by the: The National Institute
of General Medical Sciences (NIGMS) Interdisciplinary Training Grant for Biostatisticians (T32 GM74905); NIH National Institute on Aging (AG057902, AG06234, RF1AG054156, P30AG13846; supplement 0572063345, R01AG057902, R01AG061028, K23AG046377, R01AG1649, R21HD089088, F32NS096803); NIH
National Institute of Neurological Disorders and Stroke (U54NS115266, U01NS086659, U01NS093334, K23NS102399, R01NS078337, R56NS078337); National Institute of Aging Boston University AD Center (P30AG13846; supplement 0572063345-5); Department of Veterans Affairs (I01 CX001135, CSP 501,
B6796?C); Department of Defense (W81XWH?13?2?0095, W81XWH?13?2?0064, W81XWH1810580, PRARP?13267017); the Nick and Lynn Buoniconti Foundation;
and BU-CTSI Grant Number 1UL1TR001430.
========================================================================== Story Source: Materials provided by
Boston_University_School_of_Medicine. Note: Content may be edited for
style and length.
========================================================================== Journal Reference:
1. Jessica LeClair, Jennifer Weuve, Matthew P Fox, Jesse Mez, Michael L
Alosco, Chris Nowinski, Ann McKee, Yorghos Tripodis. Selection
Bias Analysis Supports Dose-Response Relationship between Level
of American Football Play and Chronic Traumatic Encephalopathy
Diagnosis. American Journal of Epidemiology, 2022; DOI:
10.1093/aje/kwac075 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220428103958.htm
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