Cognitive Performance During Night Work in the Cold

Objective: The objective of this study was to investigate how night work at low ambient temperatures affects cognitive performance (short-term memory and reaction time), skin- and core temperature, thermal comfort, sleepiness, and cortisol. We hypothesized that cognitive performance is reduced at night compared with daytime and worsened when exposed to low ambient temperatures.Method: Eleven male subjects were recruited to perform three tests in a climatic chamber at night and daytime: Night –2°C, Night 23°C and Day 23°C. Each test lasted 6 h. Cognitive performance (short-term memory and reaction time), skin- and core temperature, thermal sensation and comfort, cortisol levels and sleepiness were measured during the tests.Results: A lower mean skin temperature and corresponding lower thermal sensation were observed at Night –2°C compared to Day 23°C and Night 23°C. Night work caused increased sleepiness and lower cortisol levels, but was not affected by changes in ambient temperatures, thermal comfort, or skin temperatures. There was no effect of either day/night work nor ambient temperature on the short-term memory or reaction time test.Conclusion: Lower skin- and core temperature were observed at night when exposed to low ambient temperature (–2°C), but there was no effect on short-term memory or reaction time. Increased sleepiness and lower cortisol levels were observed at night compared to daytime and was not influenced by low ambient temperature at night. The result from this study suggests that cognitive performance (short-term memory and reaction time) is not adversely affected by night work when exposed to low ambient temperatures if adequate protective clothing is worn.

Analysis of microcirculatory disorders in men with more than 10 years’ experience on night work

Aim. To study the nature and extent of the effects of long-term sleep and wake phase disorders (working at night for more than 10 years) on the characteristics of microcirculation in men. Methods. Laser Doppler flowmetry and spectophotometry, optical tissue oximetry, and laser-induced fluorescence spectroscopy were performed in 34 male patients with a mean age of 40.30.9 years and more than 10 years experience of night work to assess the effectiveness of microcirculation. 25 men with a mean age of 40.21.2 without night work experience were used as a control group. Microcirculation was studied on the laser diagnostic complex LAKK-M (LAZMA, Russian Federation). The measurement was carried out on the skin of the palmar surface of the terminal phalanx of the second finger of the hand. The following indicators were analyzed in automatic mode: the mean perfusion value, the index of specific oxygen consumption in the tissue, capillary blood saturation, the relative volume of the red blood cell fraction, arterial blood oxygen saturation, the index of perfusion oxygen saturation in the microcirculation, the efficiency of oxygen exchange and the fluorescent indicator of oxygen consumption. Statistical processing of the results was carried out using the Student's t-test for independent samples. Results. In patients working at night for more than 10 years, a decrease in microcirculation efficiency was revealed. The index of specific oxygen consumption in the tissue was lower than that of healthy volunteers by 34.1% (p=0.000255), and the index of oxygen exchange efficiency by 56.3% (p 0.001). Long-term night work (10 years) can lead to violations of microcirculation parameters and an irreversible decrease in the efficiency of oxygen exchange compared with the control group by an average of 56.3% (18.00.5 for the group with night work experience, 41.20.6 for the group of healthy volunteers, p 0.001), the index of specific oxygen consumption in the tissue by an average of 34.1% (1.530.03 for the group with night work experience, 2.320.2 for the group of healthy volunteers, p=0.000255) and an increase in the index of perfusion oxygen saturation in the microcirculation by 2 times compared with the control group (6.20.05 for the group with night work experience, 3.670.09 for the group of healthy volunteers, p 0.001), which is accompanied by an increase in the saturation of mixed (and venous) blood. Conclusion. The nature of the revealed violations of microcirculatory parameters in the long-term night work suggests their significance in the development of diseases that are currently attributable to the so-called group of diseases of civilization.

Stability and Change of the Personality Traits Languidity and Flexibility in a Sample of Nurses: A 7–8 Years Follow-Up Study

The traits languidity (tendency to become tired/sleepy upon losing sleep) and flexibility (ability to sleep and work at odd times) have been implicated in shift work tolerance. However, there is a dearth of knowledge about their temporal stability. The aim of the present study was to explore these traits during a long follow-up (FU) period and identify factors related to potential changes in trait scores over time. In all, 1,652 nurses completed the Circadian Type Inventory-revised (CTI-r), which measures languidity and flexibility, at both 2008/2009 (baseline, BL) and again in 2016 (FU). The latent scores of these two constructs at BL, in addition to age, sex, childcare responsibility, marital status, night work status, and insomnia status, were regressed on the corresponding latent scores at follow-up using a structural equation modeling (SEM) approach. Stability was found for both languidity (rho = 0.59) and flexibility (rho = 0.58). Both composite scores declined significantly from baseline (20.62 and 12.48) to follow-up (19.96 and 11.77). Languidity at baseline was positively associated with languidity at follow-up (β = 0.89, p < 0.009). Undertaking childcare responsibility between baseline and follow-up was inversely related to languidity at follow-up (β = −0.09, p < 0.05). Starting night work was positively related to languidity at follow-up (β = 0.06, p < 0.05). Developing insomnia between baseline and follow-up (β = 0.15, p < 0.05) was positively, whereas remitting from insomnia during the same period was negatively (β = −0.11, p < 0.01) associated with languidity at follow-up. Flexibility at baseline was positively associated with flexibility at follow-up (β = 0.64, p < 0.05). Having childcare responsibility at baseline, but not at follow-up was inversely related to flexibility at follow-up (β = −0.05 p < 0.05). Becoming cohabitant with a partner between baseline and follow-up (β = −0.07, p < 0.05) was negatively associated with flexibility at follow-up. Starting night work between baseline and follow-up (β = 0.17, p < 0.01) and reporting night work at both baseline and follow-up (β = 0.18, p < 0.01) were both positively associated with flexibility at follow-up, whereas stopping working nights was negatively (β = −0.09, p < 0.05), associated with flexibility at follow-up. The personality traits languidity and flexibility show fairly high stability, albeit the mean scores were significantly reduced during the 7–8 years follow-up period. The results suggest that these personality traits are partly modifiable.