Twenty-four-hour pattern of operations-related injury occurrence and severity of off-site/on-call volunteer French firefighters.

We assessed the 24-h pattern of operations-related injuries (ORI) experienced by scheduled off-site/on-call French volunteer firefighters (VFF) through analysis of an archival database. Occurrence and severity - evaluated by number of lost work days (LWD) and total medical costs (TMC) - of ORI were explored in terms of risk ratios, respectively, number of ORI/number of service operations (RRORI), number of LWD/number of ORI (RSLWD,) and TMC/number of ORI (RSTMC). Additionally, the collective work performance of all involved VFF was measured in terms of the lag time (LT) between emergency call-center firefighter-answered communication for service of observer-presumed out-of-hospital cardiac arrest (OHCA) and departure of vehicle from fire station to render aid, designated LTOHCA. Cosinor and cross-correlation statistical methods were applied. A total of 252 ORI occurred while performing 146,479 service operations. High-amplitude 24 h variation was detected in RRORI (p < .003), SRLWD (p < .001), SRTMC (p < .012), and LTOHCA (p < .001), all with nocturnal peak time. Coherence was found between the day/night variation of LTOHCA and RRORI (r = 0.7, p < .0002), SRLWD (r = 0.5, p < .02), and SRTMC (r = 0.4, p < .05). This investigation verifies the occurrence and severity of ORI of scheduled off-site/on-call VFF exhibit high-amplitude 24 h patterning with nocturnal excess that closely coincides with their day/night work performance measured by LTOHCA. These findings, which are essentially identical to ones of a previous study entailing on-site/on-call career firefighters, indicate the need for fatigue management and ORI prevention programs not yet available to VFF, who compose the majority of the field service workforce of French fire departments. Abbreviations:FF: firefighters; CFF: career firefighters; VFF: volunteer firefighters; FD: fire department; LTOHCA: lag time (LT) response in min:sec between fire department call-center-answered communication for service of presumed out-of-hospital cardiac arrest (OHCA) and departure from fire station of vehicle to render aid; LWD: lost work days; ORI: operations-related injuries; SRLWD: severity ratio of operations-related injuries in terms of number of lost work days, calculated as number of lost work days/number of operations-related injuries; RRORI: risk ratio of operations-related injuries calculated as number of operations-related injuries/number of operations; SRTMC: severity ratio of operations-related injuries in terms of total medical costs, calculated as total medical costs/number of operations-related injuries; TMC: total medical costs.

Chronobiologic perspectives of black time--Accident risk is greatest at night: An opinion paper.

Simon Folkard in 1997 introduced the phrase black time to draw attention to the fact that the risk of driving accidents (DA) is greater during the night than day in usually diurnally active persons. The 24 h temporal pattern in DA entails circadian rhythms of fatigue and sleep propensity, cognitive and physical performance, and behavior that are controlled, at least in part, by endogenous clocks. This opinion paper extends the concept of black time to reports of excess nighttime accidents and injuries of workers and nocturnal occurrence of certain man-caused catastrophes. We explore the chronobiology of work-related black time accidents and injuries taking into account laboratory and field investigations describing, respectively, circadian rhythms in cognitive performance and errors and mistakes by employees in the conduct of routine occupational tasks. Additionally, we present results of studies pertaining to 24 h patterns of both the number and relative risk (number of events per h/number of workers exposed per h) of work-related accidents (WRA) and injuries (WRI) as well as indices of performance and alertness of a self-selected homogenous survivor cohort of French firefighters (FFs) to explore two possible explanations of black time, namely, 24 h variation in sleep propensity/drossiness characterized by a nocturnal peak and circadian rhythms in cognitive performance characterized by a nocturnal trough. We propose the 24 h pattern of WRA and WRI, particularly of FFs and other highly skilled self-selected cohorts, is more strongly linked to circadian rhythms of fatigue and sleepiness than cognitive performance. Other possible explanations--suppressed expression of circadian rhythms and/or unmasking of ultradian periodicities in cognitive performance in specific circumstances, e.g., highly stressful work, competitive, or life-threatening settings, are also discussed.

Circadian time organization of professional firemen: desynchronization-tau differing from 24.0 hours-documented by longitudinal self-assessment of 16 variables.

We investigated the circadian synchronization/desynchronization (by field-study assessment of differences in period, τ, of 16 coexisting and well-documented rhythms) of 30 healthy firemen (FM) exposed to irregular, difficult, and stressful nocturnal work hours who demonstrated excellent clinical tolerance (allochronism). Three groups of FM were studied (A = 12 FM on 24-h duty at the fire station; B = 9 FM on 24-h duty at the emergency call center; C = 9 day-shift administrative FM) of mostly comparable average age, body mass index, career duration, chronotype-morningness/eveningness, and trait of field dependence/independence. The self-assessed 16 circadian rhythms were (i) physiological ones of sleep-wake (sleep log), activity-rest (actography), body temperature (internal transmitter pill probe), right- and left-hand grip strength (hand dynamometer), systolic and diastolic blood pressure (BP) plus heart rate (ambulatory BP monitoring device); (ii) psychological ones (visual analog self-rating scales) of sleepiness, fatigue, fitness for work, and capacity to cope with aggressive social behavior; and (iii) cognitive ones of eye-hand skill and letter cancellation, entailing performance speed (tasks completed/unit time) and accuracy (errors). Data (4-6 time points/24 h; 2 591 480 values in total) were gathered continuously throughout two 8-d spans, one in winter 2010-2011 and one in summer 2011. Each of the resulting 938 unequal-interval time series was analyzed by a special power spectrum analysis to objectively determine the prominent τ. The desynchronization ratio (DR: number of study variables with τ = 24.0 h/number of study variables × 100) served to ascertain the strength/weakness of each rhythm per individual, group, and season. The field study confirmed, independent of group and season, coexistence of rather strong and weak circadian oscillators. Interindividual differences in DR were detected between groups and seasons (χ(2), correlation tests, analysis of variance [ANOVA]). Moreover, in each group, both in winter and summer, a normal distribution was observed in the number of FM with rhythms with τ = 24.0 h, e.g., ranging from 5/16 (large desynchronization) to 16/16 (no desynchronization). Such a normal distribution with intraindividual stability over time (i.e., seasons) is consistent with the hypothesis of an inherited origin of a differential propensity to circadian desynchronization and which is supported by the distribution of τs in winter and summer following the Dian-Circadian Genetic Model, i.e., with τ = 24.0 h, τ = 24.0 h + n(0.8 h), and τ = 24.0 h - n(0.8 h).

Daily rhythmicity of attention in morning- vs. evening-type adolescents at boarding school under different psychosociological testing conditions.

This study used a single protocol to investigate the respective and related effects of the psychosocial conditions of testing (individual vs. group) and personality on the levels and daily variation of attentional performance of adolescents attending boarding school. From scores obtained on an adapted version of Horne and Ostberg's Morningness-Eveningness Questionnaire (MEQ), 17 male (9 morning-type and 8 evening-type) participants were selected from among 50 volunteers. Attention was measured using a number crossing-out test carried out at four times of the day (07:30, 12:00, 14:00, and 19:30). No main effect of testing mode and personality trait was found on the mean level of performance. Time-of-day had an effect on the level of performance, which differed depending on whether the test was administered in a group or individually and on the morningness and eveningness dimension. The difference between the daily profiles appears to be dependent on the interaction of the factors studied. This study investigated the concept of "group psychological rhythmicity" and highlights the importance of synchronizing social rhythms.

Effects of alcohol on psycho-technical tests and social communication in a festive situation: a chronopsychological approach.

The aim of this study was to determine the effect of consuming alcoholic vs. nonalcoholic beverages on performance of psycho-technical tasks (attentional and general nonverbal intelligence tasks) and social behavior at different times of day. Both alcoholic and nonalcoholic consumption took place in a largely festive situation. The experiment was conducted on 184 degree-level and postgraduate students (94 female and 90 male) divided into eight independent groups for study at different times: 8:00 to 11:00, 11:00 to 14:00, 14:00 to 17:00, 17:00 to 20:00h. The main result obtained, by analysis of variance (ANOVA), showed that time of day had no effect on the performance of psycho-technical tasks nor on social communication, except for the retest situation in the attentional task. Alcohol (equal to approximately 0.5 g/L of blood) facilitated communication, but basically it had no effect on any of the psycho-technical performance tests. For the latter, an interaction was observed between when the test was done and type of beverage consumed. Alcohol appears to alter the expected change in performance in the retest situation. The results suggest that the body's sensitivity to a measured quantity of alcohol differs according to the cognitive processes involved.