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Funding Bias in TASER Research American Heart Journal 2011

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Funding source and author affiliation in TASER
research are strongly associated with a conclusion of
device safety
Peyman N. Azadani, MD, Zian H. Tseng, MD, Simon Ermakov, BA, Gregory M. Marcus, MD, and Byron K. Lee, MD
San Francisco, CA

Background Controversy exists regarding the safety of electrical stun guns (TASERs). Much of the research on TASERs is
funded by the maker of the device and, therefore, could be biased. We sought to determine if funding source or author
affiliation is associated with TASER research conclusions.
Methods MEDLINE was searched for TASER or electrical stun gun to identify relevant studies. All human and animal
studies published up to September 01, 2010, were included. Reviews, editorials, letters, and case reports were excluded from
the analysis. Two independent reviewers blinded to this study hypothesis evaluated each article with regard to conclusions of
TASER safety.
Results Fifty studies were reviewed: 32 (64%) were human studies and 18 (36%) were animal studies. Twenty-three (46%)
studies were funded by TASER International or written by an author affiliated with the company. Of these, 22 (96%) concluded
that TASERs are unlikely harmful (26%) or not harmful (70%). In contrast, of the 22 studies not affiliated with TASER, 15 (55%)
concluded that TASERs are unlikely harmful (29%) or not harmful (26%). A study with any affiliation with TASER International
had nearly 18 times higher odds to conclude that the TASER is likely safe as compared with studies without such affiliation
(odds ratio 17.6, 95% CI 2.1-150.1, P = .001).

Studies funded by TASER and/or written by an author affiliated with the company are substantially more
likely to conclude that TASERs are safe. Research supported by TASER International may thus be significantly biased in favor of
TASER safety. (Am Heart J 2011;162:533-7.)

Conducted electrical weapons are used worldwide
by law enforcement agencies to incapacitate violent,
combative individuals. The deployment of these
devices by police departments is increasing.1 TASERs,
the most popular brand of electrical stun guns,
deliver electrical pulses leading to stimulation of both
sensory and motor nervous system and involuntary
muscle contractions.2
Research studies thus far on TASERs have had conflicting results. Although some have found that TASER
deployment is associated with an increased risk of
injuries and sudden death,3-5 others concluded that
these devices cause no significant harm.6,7
A substantial number of studies on the TASER are
funded by the manufacturer of the device, TASER

From the University of California, San Francisco, School of Medicine, San Francisco, CA.
Submitted February 26, 2011; accepted May 21, 2011.
Reprint requests: Byron K. Lee, MD, UCSF Cardiac Electrophysiology and Arrhythmia
Service 500 Parnassus Avenue Box 1354, MUE 429 San Francisco, CA 94143-1354.
0002-8703/$ - see front matter
© 2011, Mosby, Inc. All rights reserved.

International. It has been suggested that this may have led
to bias.8 We sought to determine whether funding from
TASER International or author affiliation with the
company is associated with the conclusion that the
device is safe.

Article selection
TASER literature was identified by searching the National
Library of Medicine's MEDLINE for terms TASER and stun
gun. All peer-reviewed articles including human and animal
studies published up to September 01, 2010, were
included. Exclusion criteria were established before study
inclusion and data analysis. All review articles, editorial
letters, and case reports were excluded. No language
restriction was imposed.

Article assessment
The entire manuscript including the conflict of interest
statement and acknowledgment section of all articles were
reviewed by 2 independent reviewers. A study was classified as
having a TASER-affiliated author if one or more of the authors
either had received funding from the company or had disclosed

American Heart Journal
September 2011

534 Azadani et al

Figure 1

150 citations was found in
Medline using search terms:
TASER, Stun gun
34 excluded based on Title and
116 potentially relevant
studies for more detailed
66 excluded for the following reasons:
22 Case reports
14 Review articles
18 Editorial letters
3 Reports
8 Non-in vivo studies
1 Technical note
50 articles were included in
the analysis

Study flow chart.

a financial relationship with the company somewhere in the
article. The assessment of funding source and author affiliation
was not based on any data beyond what was disclosed in the
articles. Studies either fully or partially funded by TASER
International were considered TASER funded.

and 95% CIs of dichotomous outcomes. Two-tailed P b .05 was
considered significant.
No extramural funding was used to support this work.
The authors are solely responsible for the design and conduct
of this study, all study analyses, the drafting and editing of the
manuscript, and its final contents.

Article conclusions
Two independent reviewers blinded to the hypothesis of our
study evaluated each article's conclusions regarding the safety of
TASERs. Based on the results and conclusion sections, the study
outcomes were classified as harmful, probably harmful, unlikely
harmful, and not harmful. Study outcomes of unlikely harmful
and not harmful were considered a conclusion of safety. If the 2
reviewers classified the conclusions of an article differently, a
third independent reviewer decided which of the 2 preliminary
classifications would be used for analysis.

Statistical analysis
Statistical analyses were performed using SPSS software for
Windows version 16. χ2 Analyses were conducted to compare
proportions to test the null hypothesis that TASER affiliation is
not related to conclusion about safety of TASERs. Logistic
regression analysis was performed to calculate odds ratios (ORs)

A total of 119 published articles on TASER were
identified in the literature. Sixty-nine articles did not
meet the inclusion criteria for the reasons shown in
Figure 1, leaving 50 publications retained for
analysis.3-7,9-53 Descriptive characteristics of the studied
articles are shown in Table I. All the studied articles
were written in English.
Thirty-two (64%) of the articles reported human
studies, and 18 (36%) reported studies performed on
animals. Overall, 23 (46%) of the articles were funded
by TASER or authored by an affiliate of the company
(Table II). Twenty-two (96%) of these articles concluded
that TASERs are unlikely harmful (26%) or not harmful
(70%). In contrast, of the 27 studies not affiliated with

American Heart Journal
Volume 162, Number 3

Azadani et al 535

Table I. Descriptive characteristic of articles on TASER

Figure 2

Articles (N = 50)
P = .001

Study population, n (%)
Author affiliation, n (%)
Funding source, n (%)
No funding
Conclusion, n (%)
Probably harmful
Unlikely harmful
Not harmful


32 (64)
18 (36)


14 (28)
11 (22)
25 (50)


Values are presented as n (%).



19 (38)
31 (62)




TASER affiliation
not harmful

No TASER affiliation

Proportion of TASER articles with device-safety conclusions.
Table II. Level of safety by any commercial affiliation
TASER affiliation
Probably harmful
Unlikely harmful
Not harmful

Yes (n = 23)
0 (0)
1 (4)
6 (26)
16 (70)

No (n = 27)


Values are presented as n (%).

TASER International, 15 (55%) found that TASERs are
unlikely harmful (29%) or not harmful (26%).
TASER-supported articles included a similar number of
patients as studies without TASER affiliation (mean of 129
vs 166, P = .40). Shown in Figure 2, a study with any
affiliation with TASER International had 17.6 times
greater odds of concluding that the TASER is likely safe
as compared with studies without such affiliation (95% CI
2.1-150.1, P = .001). This corresponds to a 75% greater
probability that studies with TASER affiliation would
conclude that the TASER is unlikely or not harmful.

With the rapid expansion of stun gun deployment by
law enforcement agencies, several research studies have
been performed to determine the safety of these devices.
Many of these studies are funded by TASER International,
which manufactures and markets the stun gun most
commonly used by law enforcement in the United States.
In our study, any affiliation with TASER International was
strongly associated with concluding that TASERs are safe.
This finding demonstrates that TASER International
funding source and/or author affiliation may have a
great influence on article conclusions.

Although the safety of electronic control devices
including TASERs has been investigated by several
studies, controversy still exists as to whether TASERs
can cause serious injuries. Some investigations have
demonstrated that TASERs are safe with regard to cardiac
arrhythmias, respiratory arrest, rhabdomyolysis, and
acidosis.9-12 However, all such studies were performed
on animals or healthy volunteers, and the results would
be difficult to extrapolate to the stressful circumstances
during an arrest. Furthermore, many of these studies
were supported by TASER International or authors
affiliated with the company, which may influence the
results and conclusions.13-16 On the other hand, several
studies have concluded that TASER deployment is
dangerous, with the potential to cause ventricular
fibrillation and sudden death.4,5,17,18 There are also 22
case reports describing injuries associated with the
TASER, most of which were not funded by the TASER
International.54-56 Notably, these case reports were
excluded from our analysis.
There are several possible explanations for the
disparate conclusions of the 2 groups of studies. The
first possibility is that the literature may be biased; either
research supported by TASER was done in a way to
misleadingly conclude that the TASER is safe or likely safe
or research performed by independent investigators was
done in a way to misleadingly conclude that the TASER is
harmful or likely harmful. It is clear why researchers
being funded by TASER International or being paid by the
company might have a tendency to bias their research in
favor of the TASER. It is less evident the incentive for
researchers without an affiliation with the TASER
International to bias their research against TASER,
although one might hypothesize that they strive for
recognition for provocative research. Furthermore, some
of these authors may serve as expert witnesses in lawsuits

American Heart Journal
September 2011

536 Azadani et al

against TASER International and thereby have secondary
gain from vilifying the device. We were unable to
accurately ascertain which authors were serving as
expert witnesses in court cases.
The other possibility is that the study protocols chosen
led to disparate conclusions about the TASER. It is
possible that the authors who were funded by TASER
International or had a financial affiliation devised study
protocols more likely to show that the TASER is safe,
whereas the authors with no affiliation with the company
may have devised study protocols more likely to show
that the TASER is harmful. For example, some of the
TASER-funded studies examined the effects of healthy
humans being stunned in the back, distant from the
cardiac axis and thus unlikely to have significant effects
on the heart.9,19 In contrast, some animal studies analyzed
the effect of TASER discharges very close to the heart in
anesthesized pigs.4,5 Swine hearts are more prone to
ventricular tachyarrhythmia than those of humans,57 and
therefore, the choice of a pig model may make the TASER
seem more dangerous.
The other explanation for this discrepancy is that
studies sponsored by TASER International might have
been less likely to be published if they found possible
harm than if they found safety.

Study limitations
Our study has several important limitations. First, our
analysis is based on a relatively small sample size. Given
limited published articles in this field, further studies
are required with regard to the safety of TASERs.
Second, the studies included in our analysis differ from
each other in terms of study design and methodology.
This heterogeneity makes comparison of the conclusions in these studies more difficult. Finally, the
determination of funding source or author affiliation
may have been incomplete or inaccurate. We relied
primarily on the disclosures in the journal article, which
may be unreliable.

These data demonstrate that studies funded by TASER
International or written by authors affiliated with the
company are nearly 18 times more likely to conclude that
TASERs are safe. Research supported by TASER International may thus be significantly biased in favor of TASER
safety. Readers of articles about the TASER should
consider funding and author affiliations in their evaluation of the article's conclusions.

No conflict of interest; No financial support.

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