Potentially Psychologically Traumatic Event Exposure Histories of new Royal Canadian Mounted Police Cadets.

OBJECTIVE: Royal Canadian Mounted Police (RCMP) report extremely frequent and varied exposures to potentially psychologically traumatic events (PPTEs). While occupational exposures to PPTEs may be one explanation for the symptoms of mental disorders prevalent among serving RCMP, exposures occurring prior to service may also play a role. The objective of the current study was to provide estimates of lifetime PPTE exposures among RCMP cadets in training and assess for associations with mental disorders or sociodemographic variables. METHODS: RCMP cadets (n = 772; 72.0% male) beginning the Cadet Training Program (CTP) completed a survey assessing self-reported PPTE exposures as measured by the Life Events Checklist for the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition-Extended. Binomial tests were conducted to compare the current results to previously collected data from the general population, a diverse sample of public safety personnel (PSP) and serving RCMP. RESULTS: Cadets reported statistically significantly fewer PPTE exposures for all PPTE types than serving RCMP (all p's < 0.001) and PSP (all p's < 0.001) but more PPTE exposures for all PPTE types than the general population (all p's < 0.001). Cadets also endorsed fewer PPTE types (6.00 ± 4.47) than serving RCMP (11.64 ± 3.40; p < 0.001) and other PSP (11.08 ± 3.23) but more types than the general population (2.31 ± 2.33; p < 0.001). Participants who reported being exposed to any PPTE type reported the exposures occurred 1-5 times (29.1% of participants), 6-10 times (18.3%) or 10 + times (43.1%) before starting the CTP. Several PPTE types were associated with positive screens for one or more mental disorders. There were associations between PPTE types and increased odds of screening positive for post-traumatic stress disorder (PTSD), major depressive disorder (MDD), generalized anxiety disorder (GAD) and social anxiety disorder (SAD) (all p's < 0.05). Serious transport accident (11.1%), physical assault (9.5%) and sudden accidental death (8.4%) were the PPTEs most identified as the worst event, and all were associated with positive screens for one or more mental disorders. CONCLUSION: The current results provide the first information describing PPTE histories of cadets, evidencing exposure frequencies and types much higher than the general population. PPTE exposures may have contributed to the cadet's vocational choices. The current results support the growing evidence that PPTEs can be associated with diverse mental disorders; however, the results also suggest cadets may be uncommonly resilient, based on how few screened positive for mental disorders, despite reporting higher frequencies of PPTE exposures prior to CTP than the general population.

Long-term effects of multiple concussions on prefrontal cortex oxygenation during a hypercapnic challenge in retired contact sport athletes.

This exploratory study aimed to investigate the long-term effects of multiple concussions on prefrontal cortex oxygenation during a five-minute hypercapnic challenge using Near Infrared Spectroscopy (NIRS). 55 physically active retired contact sport male athletes with three or more previous concussions (mTBI) were recruited along with 29 physically active males with no concussions history (CTRL). Participants completed five minutes of seated rest prior to the five-minute hypercapnic challenge (20-second breath-hold, 40-second recovery breathing; five times). NIRS measured right and left side oxygenated (O2Hb), deoxygenated (HHb), total (tHb) haemoglobin, and haemoglobin difference (HbDiff) with all parameters analysed through changes in average maximal and minimal values (ΔMAX), Z-scores, and standard deviations. Right prefrontal cortex HbDiff ΔMAX was significantly higher in the mTBI compared to CTRL (p = 0.045) group. Left prefrontal cortex O2Hb ΔMAX (p = 0.040), HHb Z-Scores (p = 0.008), and HbDiff ΔMAX(p = 0.014) were significantly higher in the mTBI group. Within-group right vs left analyses demonstrated significantly lower left HbDiff ΔMAX (p = 0.048) and HbDiff Z-scores (p = 0.002) in the mTBI group, while the CTRL group had significantly lower left HHb Z-scores (p = 0.003) and left tHb Z-scores (p = 0.042). This study provides preliminary evidence that athletes with a history of three or more concussions may have impaired prefrontal cortex oxygenation parameters during a hypercapnic challenge.

Firefighter pre-frontal cortex oxygenation and hemodynamics during rapid heat stress.

This study evaluated the impact of rapid heat stress on prefrontal cortex (PFC) oxygenation and hemodynamics. Previous work has demonstrated that heat stress affects cerebral oxygenation and hemodynamics. Fourteen male subjects performed a graded exercise test to a termination criterion (volitional maximum, core temperature = 39.5 °C, or a 2-hour time cap) with (GEAR) and without (NOGEAR) firefighting gear in a laboratory with an ambient temperature of 25-26 °C. Changes in oxyhemoglobin (O2Hb), total hemoglobin (tHb), and tissue oxygen saturation index (TSI %) were monitored in the left and right PFC using near-infrared spectroscopy (NIRS). Significant NIRS results were a plateau in the left-side O2Hb and tHb at 80 % of the time to termination (TTT) in NOGEAR, and 60 % of TTT in GEAR. These TTT points were when the subject's core temperature (Tc) was equal to 38 °C. Additionally, there was higher left-side PFC activation during GEAR, as indicated by a significant decrease in TSI % from start to end of exercise and double the reduction in TSI % per minute in PPE compared to NOGEAR. There were no significant differences during the NOGEAR session. These data suggest that a rapid heat stress scenario (GEAR) causes altered cerebral oxygenation and hemodynamic response in the left-side PFC. The left PFC could be working harder to prevent fatigue in GEAR. This could affect cognitive processes during or following exercise in the heat while wearing personal protective equipment. Our results also support previous research demonstrating that NIRS is a sensitive metric of fatigue.

Prefrontal cortex oxygenation during incremental exercise in chronic fatigue syndrome.

This study examined the effects of maximal incremental exercise on cerebral oxygenation in chronic fatigue syndrome (CFS) subjects. Furthermore, we tested the hypothesis that CFS subjects have a reduced oxygen delivery to the brain during exercise. Six female CFS and eight control (CON) subjects (similar in height, weight, body mass index and physical activity level) performed an incremental cycle ergometer test to exhaustion, while changes in cerebral oxy-haemoglobin (HbO2), deoxy-haemoglobin (HHb), total blood volume (tHb = HbO2 + HHb) and O2 saturation [tissue oxygenation index (TOI), %)] was monitored in the left prefrontal lobe using a near-infrared spectrophotometer. Heart rate (HR) and rating of perceived exertion (RPE) were recorded at each workload throughout the test. Predicted VO2peak in CFS (1331 +/- 377 ml) subjects was significantly (P < or = 0.05) lower than the CON group (1990 +/- 332 ml), and CFS subjects achieved volitional exhaustion significantly faster (CFS: 351 +/- 224 s; CON: 715 +/- 176 s) at a lower power output (CFS: 100 +/- 39 W; CON: 163 +/- 34 W). CFS subjects also exhibited a significantly lower maximum HR (CFS: 154 +/- 13 bpm; CON: 186 +/- 11 bpm) and consistently reported a higher RPE at the same absolute workload when compared with CON subjects. Prefrontal cortex HbO2, HHb and tHb were significantly lower at maximal exercise in CFS versus CON, as was TOI during exercise and recovery. The CFS subjects exhibited significant exercise intolerance and reduced prefrontal oxygenation and tHb response when compared with CON subjects. These data suggest that the altered cerebral oxygenation and blood volume may contribute to the reduced exercise load in CFS, and supports the contention that CFS, in part, is mediated centrally.