Today.Az » Weird / Interesting » Out-of-the-blue panic attacks aren't without warning: Body sends signals for hour before
28 July 2011 [21:16] - Today.Az
Panic attacks that seem to strike sufferers out-of-the-blue are not without warning after all, according to new research.
A study based on 24-hour monitoring of panic sufferers while they
went about their daily activities captured panic attacks as they
happened and discovered waves of significant physiological instability
for at least 60 minutes before patients' awareness of the panic attacks,
said psychologist Alicia E. Meuret at Southern Methodist University in
Dallas.
In a rare study in which patients were monitored around-the-clock,
portable recorders captured changes in respiration, heart rate and other
bodily functions, said Meuret, lead researcher on the study.
The new findings suggest sufferers of panic attacks may be highly
sensitive to -- but unaware of -- an accumulating pattern of subtle
physiological instabilities that occur before an attack, Meuret said.
Monitoring data also showed patients were hyperventilating on a chronic
basis.
"The results were just amazing," Meuret said. "We found that in this
hour preceding naturally occurring panic attacks, there was a lot of
physiological instability. These significant physiological instabilities
were not present during other times when the patient wasn't about to
have a panic attack."
It is notable that patients reported the attacks as unexpected,
lacking awareness of either the coming attack or their changing
physiology.
"The changes don't seem to enter the patient's awareness," Meuret
said. "What they report is what happens at the end of the 60 minutes --
that they're having an out-of-the blue panic attack with a lot of
intense physical sensations. We had expected the majority of the
physiological activation would occur during and following the onset of
the panic attack. But what we actually found was very little additional
physiological change at that time."
Unexpected attacks have been a mystery; little research to explain them
The diagnostic standard for psychological disorders, the DSM-IV,
defines panic attacks as either expected or unexpected. Those that are
expected, or cued, occur when a patient feels an attack is likely, such
as in closed spaces, while driving or in a crowded place.
"But in an unexpected panic attack, the patient reports the attack to
occur out-of-the-blue," Meuret said. "They would say they were sitting
watching TV when they were suddenly hit by a rush of symptoms, and there
wasn't anything that made it predictable."
To sufferers and researchers alike, the attacks are a mystery.
Change-point analysis uncovered physiological instabilities one hour before attacks
Meuret and her colleagues discovered the significant physiological
instabilities using change-point analysis, a statistical method that
searches for points when changes occur in a "process" over time.
"This analysis allowed us to search through patients' physiological
data recorded in the hour before the onset of their panic attacks to
determine if there were points at which the signals changed
significantly," said psychologist David Rosenfield of SMU, lead
statistician on the project.
The study is significant not only for panic disorder, but also for
other medical problems where symptoms and events have seemingly
"out-of-the blue" onsets, such as seizures, strokes and even manic
episodes.
"I think this method and study will ultimately help detect what's
going on before these unexpected events and help determine how to
prevent them," Meuret said. "If we know what's happening before the
event, it's easier to treat it."
Meuret, an assistant professor in the SMU Department of Psychology,
reported the results in the journal Biological Psychiatry in the article
"Do Unexpected Panic Attacks Occur Spontaneously?" Rosenfield is an
associate professor in SMU's Department of Psychology.
A multi-disciplinary collaboration, other authors on the study were
psychologist Thomas Ritz, SMU Department of Psychology; psychologist
Frank H. Wilhelm, University of Salzburg, Austria; electrical engineer
Enlu Zhou, University of Illinois at Urbana-Champaign; and psychologist
Ansgar Conrad and psychiatrist Walton T. Roth, both of Stanford
University.
Subtle physical changes impact panic sufferers more severely
People with panic disorder probably won't be surprised by the results, Meuret said.
By definition, the majority of the 13 symptoms of panic attack are
physiological: shortness of breath, heart racing, dizziness, chest pain,
sweating, hot flashes, trembling, choking, nausea and numbness. Only
three are psychological: feeling of unreality, fear of losing control
and fear of dying.
"Most patients obviously feel that there must be something going on
physically," Meuret said. "They worry they're having a heart attack,
suffocating or going to pass out. Our data doesn't indicate there's
something inherently wrong with them physically, neither when they are
at rest nor during panic. The fluctuations that we discovered are not
extreme; they are subtle. But they seem to build up and may result in a
notion that something catastrophic is going on."
Notably, the researchers found that patients' carbon dioxide, or C02,
levels were in an abnormally low range, indicating the patients were
chronically hyperventilating. These levels rose significantly shortly
before panic onset and correlated with reports of anxiety, fear of dying
and chest pain.
"It has been speculated, but never verified with data recordings in
daily life, that increases in CO2 cause feelings of suffocation and can
be panic triggers," Meuret said.
Fanny pack monitor tracked physiological changes before, during and after attacks
To capture the physiological data, 43 patients wore the monitoring
devices for 24 hours on two separate occasions. The researchers
collected 1,960 hours of ambulatory monitoring data, including 13
unexpected panic attacks.
Participants, all of whom suffer from panic disorder, were each
outfitted with an array of electrodes and sensors attached to various
parts of their bodies.
The ambulatory monitoring device was toted in a small waist pack the
patients wore. Also included was a portable capnometer to measure CO2
collected from exhaled breath. The physiological responses were recorded
continuously as digital data in a time series.
Each monitoring pack included a "panic button." Patients were
instructed to press the button if they had an attack and to write down
their symptoms. By triggering the panic button, patients inserted a
marker into the time-series data, marking the moment the attack began.
The sensors measured eight physiological indices, including changes
in respiration, such as how deep, fast or irregular people were
breathing; cardiac activity; and evidence of sweating.
Data analysis found strikingly significant changes in the hour before attacks
From the nearly 2,000 hours of data, the change-point analysis
program allowed the researchers to slice out 70-minute periods around
each of the 13 panic attacks ??? from one hour before onset until 10
minutes after the attacks began.
For each index, the program checked for any significant change in the
signal that remained stable over a specified period of time.
Those results were collapsed across all 13 panic attacks, with
minute-by-minute averages. The information was then compared to a
70-minute control period randomly chosen during non-panic periods.
"We found 15 subtle but significant changes an hour before the onset
of the panic attacks that followed a logical physiological pattern.
These weren't present during the non-panic period," Meuret said.
"Why they occurred, we don't know. We also can't say necessarily they
were causal for the panic attacks. But the changes were strikingly and
significantly different to what was observed in the non-panic control
period," she said.
Findings prompt look at "panic" definition and treatment
The study's results invite a reconsideration of the DSM diagnostic
definition that separates "expected" from "unexpected" attacks, Meuret
said.
Also, the study might explain why medication or interventions aimed
at normalizing respiration for treating panic are effective, she said.
Medication generally buffers arousal, keeping it low and regular,
thereby preventing unexpected panic attacks.
For psychological treatments such as Cognitive Behavior Therapy
(CBT), the results are more challenging. CBT requires a patient to focus
on examining thoughts to prevent an attack.
"But a patient can't work on something they don't know is going to happen," Meuret said.
New methodology can be universalized to other unexpected medical problems
The study's use of change-point analysis can be applied to other
medical issues. Traditional statistics are ineffective at analyzing such
data, Meuret said, because they look only at level differences at
pre-determined times and won't find a signal for an unknown point.
"This study is a step toward more understanding and hopefully opening
more doors for research on medical events that are difficult to
predict. The hope is that we can then translate these findings into new
therapies," she said.
The research was funded by the National Institutes of Mental Health,
Department of Veterans Affairs and the Beth and Russell Siegelman
Foundation. /Science Daily/
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