Self-reported exercise frequency and PTSD: results from the National Health and Resilience in Veterans Study

OBJECTIVE

Physical exercise may serve as a protective factor for posttraumatic stress disorder (PTSD), but little is known about whether physical exercise is associated with PTSD in population-based samples of military veterans.

METHODS

We analyzed cross-sectional data on the relation between self-reported physical exercise frequency and the prevalence of probable PTSD in a nationally representative sample of 2832 U.S. military veterans who participated in the National Health and Resilience in Veterans Study.

RESULTS

A "U-shaped" association best explained the relation between self-reported exercise frequency and the prevalence of probable PTSD. Compared to veterans without probable PTSD, those with probable PTSD were nearly twice as likely to report no weekly exercise (52.3% vs. 29.3%) or daily (7 days/week) exercise (15.2% vs. 8.5%) and were nearly half as likely to report exercising a median of 3.5 days/week (32.6% vs. 62.1%). No exercise was associated with greater severity of emotional numbing and lower severity of anxious arousal symptoms, while daily exercise was associated with greater severity of re-experiencing symptoms.

CONCLUSIONS

Results of this study suggest a "U-shaped" association between self-reported exercise frequency and the prevalence of probable PTSD among U.S. veterans. Veterans with probable PTSD were more likely than those without probable PTSD to report not exercising at all or exercising every day and were less likely to report exercising 1-6 days per week. Clinical implications of these findings are discussed.

Modeling the Optimum Prussian Blue Treatment for Acute Radiation Syndrome Following 137Cs Ingestion

Accidents or radiological attacks may lead to ingestion of Cs by large numbers of the public. This work models the efficacy of Prussian blue, the medical countermeasure for internal contamination with Cs, to prevent acute radiation syndrome as a function of the duration of treatment and the time that treatment starts after uptake. Risk of acute radiation syndrome is modeled using the International Commission on Radiological Protection's acute radiation hazard model. Dose rates to target organs from Cs ingestion were based on the data published by the US Environmental Protection Agency and the retention of Cs in the reference man. Modeling found that treatment is most effective if begun within 15 d of ingestion, and the course length should be at least 75 d to mitigate cancer risk and 290 d to mitigate fatalities due to acute radiation syndrome. Both of these course lengths are much longer than the minimum Prussian blue treatment regimen of 30 d. Extending the treatment time for contaminated individuals would increase demand for Prussian blue following an accident or attack and in turn, would require a larger stockpile of Prussian blue to meet demand. Not enough data is available to determine if this longer treatment time would lead to adverse medical outcomes due to the toxicity of the treatment itself.

Review of Cases of Occult Radiation Exposure and an Analysis of Time to Diagnosis

Radiation sickness is challenging to diagnose, and the diagnosis is often based on nonclinical data. In accidents where patients are not aware of their exposure to radiation (so-called "occult exposures"), a correct diagnosis can take weeks or months. The purpose of this study is to review the time to diagnosis of radiation sickness for occult exposures where neither the physician nor the patients are aware of their exposure. We reviewed eight case reports involving occult exposures and examined the factors that contributed to a diagnosis. We found that an average of 23 d after exposure were required for diagnosis, regardless of route of intake. In only one case was radiation injury diagnosed within the first week. Although all but one of these cases occurred in the developing world, the factors confounding diagnosis are common to the U.S. medical system. Therefore, an urgent need exists for properly training physicians on radiation sickness so they can more quickly diagnose and treat radiation exposures when the patients are unaware of the exposure event.

The role of stress in the pathogenesis and maintenance of obsessive-compulsive disorder

Individuals with obsessive-compulsive disorder often identify psychosocial stress as a factor that exacerbates their symptoms, and many trace the onset of symptoms to a stressful period of life or a discrete traumatic incident. However, the pathophysiological relationship between stress and obsessive-compulsive disorder remains poorly characterized: it is unclear whether trauma or stress is an independent cause of obsessive-compulsive disorder symptoms, a triggering factor that interacts with a preexisting diathesis, or simply a nonspecific factor that can exacerbate obsessive-compulsive disorder along with other aspects of psychiatric symptomatology. Nonetheless, preclinical research has demonstrated that stress has conspicuous effects on corticostriatal and limbic circuitry. Specifically, stress can lead to neuronal atrophy in frontal cortices (particularly the medial prefrontal cortex), the dorsomedial striatum (caudate), and the hippocampus. Stress can also result in neuronal hypertrophy in the dorsolateral striatum (putamen) and amygdala. These neurobiological effects mirror reported neural abnormalities in obsessive-compulsive disorder and may contribute to an imbalance between goal-directed and habitual behavior, an imbalance that is implicated in the pathogenesis and expression of obsessive-compulsive disorder symptomatology. The modulation of corticostriatal and limbic circuits by stress and the resultant imbalance between habit and goal-directed learning and behavior offers a framework for investigating how stress may exacerbate or trigger obsessive-compulsive disorder symptomatology.

Screening Internal Contamination of Inhaled and Ingested Radionuclides with Hand-held Survey Meters

During the aftermath of a radiological accident or attack, the rapid identification of individuals who have internalized medically significant amounts of material is paramount to guide medical and public health decisions. This paper explores the utility of hand-held, pancake GM detectors to determine if an individual has inhaled Sr, Cs, Pu, Pu, or Am in quantities requiring treatment. Additionally, ingestion of Sr or Cs was considered. Both Sr and Cs were modeled in equilibrium with their progeny, but the progeny of Pu, Pu, and Am were excluded. Treatment thresholds are defined using the National Council on Radiation Protection & Measurements' (NCRP) clinical decision guides (CDGs). Using Monte Carlo N-Particle (MCNP) modeling software, a human phantom and detector were modeled to determine the activity required to achieve a detector reading of twice background 1, 7, or 30 d post-ingestion or post-inhalation. Modeling found that inhaled Pu, Pu, and Am are detectable only if the contaminated individual inhaled thousands-fold more material than the CDG. This lack of detectability means that hand-held GM detectors are inappropriate for initial screening for americium or plutonium and that more intensive screening is necessary to confirm suspected contamination. Cesium-137, by contrast, could be detected at levels 10- to 100-fold lower than the amount requiring treatment, allowing quick differentiation between contaminated and uncontaminated individuals. Surprisingly, Sr was detectable within a factor of 2 of the amount requiring treatment. Detection of Sr was due primarily to bremsstrahlung radiation from beta interactions with calcium in bone. While rapid screening could identify individuals contaminated by Cs and possibly with Sr, further screening of identified individuals is necessary to establish medical need. However, these contaminated individuals could still be prioritized for further testing and possible presumptive treatment. Based on the findings of this study, concepts of operation for the use of hand-held survey meters should be developed for the screening of individuals potentially internally contaminated with Cs and Sr.

Estimating Risk of Hematopoietic Acute Radiation Syndrome in Children

Following a radiological terrorist attack or radiation accident, the general public may be exposed to radiation. Historically, modeling efforts have focused on radiation effects on a "reference man"-a 70-kg, 180-cm-tall, 20- to 30-y-old male-which does not adequately reflect radiation hazard to special populations, particularly children. This work examines the radiosensitivity of children with respect to reference man to develop a set of parameters for modeling hematopoetic acute radiation syndrome in children. This analysis was performed using animal studies and the results verified using data from medical studies. Overall, the hematopoietic system in children is much more radiosensitive than that in adults, with the LD50 for children being 56% to 91% of the LD50 of adults, depending on age.

Disgust mediates the relation between attentional shifting and contamination aversion

BACKGROUND AND OBJECTIVES

Aversion of contaminants is important for several psychiatric disorders, particularly contamination-based obsessive-compulsive disorder (OCD). Recent theoretical models have proposed that the ability to control one's attention, especially when processing affectively laden information, is important in the etiology of pathological anxiety. The present study tested the relations between attentional control, affective arousal, and behavioral approach toward contaminants (contamination aversion).

METHODS

Thirty-three non-selected (undergraduate university students) participants completed a measure of trait attentional control and three behavioral approach tasks, which measured emotional reactivity and approach toward contaminants.

RESULTS

Preliminary analyses showed that poorer attentional control and greater affective arousal predicted less behavioral approach toward contaminants. Modeling of direct and indirect relations showed that poor attentional shifting ability and greater subjective disgust were related to less behavioral approach. Moreover, disgust fully mediated the relation between attentional shifting and behavioral approach.

LIMITATIONS

The present study used a convenience sample, which is not representative of the general population or individuals with OCD; therefore, research using clinical samples is necessary before making clinical interpretations. Moreover, the present study utilized subjective measures of attentional control and affective arousal. The use of objective measures of attention and affective arousal would provide a more valid test of the role of attentional control in contamination aversion.

CONCLUSIONS

These findings suggest that attentional shifting abilities may serve as a vulnerability to affective arousal/regulation and behavioral avoidance of contaminants, but the latter relation only operated indirectly via disgust. These findings have clear implications for the etiology of contamination-related OCD.