Misaligned core body temperature rhythms impact cognitive performance of hospital shift work nurses.

Circadian rhythms greatly influence 24-h variation in cognition in nearly all organisms, including humans. Circadian clock impairment and sleep disruption are detrimental to hippocampus-dependent memory and negatively influence the acquisition and recall of learned behaviors. The circadian clock can become out of sync with the environment during circadian misalignment. Shift work represents a real-world model of circadian misalignment that can be studied for its physiological implications. The present study aimed to test the hypothesis that circadian misalignment disrupts vigilance and cognitive performance on occupationally relevant tasks using shift work as a model. As such, we sought to (1) explore the general effects of night- and day-shift worker schedules on sleep-wake parameters and core body temperature (CBT) phase, and (2) determine whether shift-type and CBT phase impact cognitive performance and vigilance at the end of a 12-h shift. We observed a sample of day-shift and night-shift hospital nurses over a 10-day period. At the end of three, consecutive, 12-h shifts (7 pm-7am or 7am-7 pm), participants completed a cognitive battery assessing vigilance, cognitive throughput, and medication calculation fluency (via an investigator developed and tested metric). Night-shift nurses exhibited significantly greater sleep fragmentation as well as a greater disparity between their wake-time and time of CBT minimum compared to day-shift nurses. Night-shift nurses exhibited significantly slower cognitive proficiency at the end of their shifts, even after adjustment for CBT phase. These results suggest that circadian disruption and reduced sleep quality both contribute to cognitive functioning and performance.

Comparison of Indian Council for Medical Research and Lunar Databases for Categorization of Male Bone Mineral Density.

The mainstay of diagnosis of osteoporosis is dual-energy X-ray absorptiometry (DXA) scan measuring areal bone mineral density (BMD) (g/cm2). The aim of the present study was to compare the Indian Council of Medical Research database (ICMRD) and the Lunar ethnic reference database of DXA scans in the diagnosis of osteoporosis in male patients. In this retrospective study, all male patients who underwent a DXA scan were included. The areal BMD (g/cm2) was measured at either the lumbar spine (L1-L4) or the total hip using the Lunar DXA machine (software version 8.50) manufactured by GE Medical Systems (Shanghai, China). The Indian Council of Medical Research published a reference data for BMD in the Indian population derived from the population-based study conducted in healthy Indian individuals, which was used to analyze the BMD result by Lunar DXA scan. The 2 results were compared for various values using statistical software SPSS for Windows (version 16; SPSS Inc., Chicago, IL). A total 238 male patients with a mean age of 57.2 yr (standard deviation ±15.9) were included. Overall, 26.4% (66/250) and 2.8% (7/250) of the subjects were classified in the osteoporosis group according to the Lunar database and the ICMRD, respectively. Out of the 250 sites of the DXA scan, 28.8% (19/66) and 60.0% (40/66) of the cases classified as osteoporosis by the Lunar database were reclassified as normal and osteopenia by ICMRD, respectively. In conclusion, the Indian Council of Medical Research data underestimated the degree of osteoporosis in male subjects that might result in deferring of treatment. In view of the discrepancy, the decision on the treatment of osteoporosis should be based on the multiple fracture risk factors and less reliably on the BMD T-score.