Biochemical hypoglycemia in female nurses during clinical shift work

Unaltered instrumental learning and attenuated body-weight gain in rats during non-rotating simulated shiftwork

Exposure to shiftwork has been associated with multiple health disorders and cognitive impairments in humans. We tested if we could replicate metabolic and cognitive consequences of shiftwork, as reported in humans, in a rat model comparable to 5 wks of non-rotating night shifts. The following hypotheses were addressed: (i) shiftwork enhances body-weight gain, which would indicate metabolic effects; and (ii) shiftwork negatively affects learning of a simple goal-directed behavior, i.e., the association of lever pressing with food reward (instrumental learning), which would indicate cognitive effects. We used a novel method of forced locomotion to model work during the animals' normal resting period. We first show that Wistar rats, indeed, are active throughout a shiftwork protocol. In contrast with previous findings, the shiftwork protocol attenuated the normal weight gain to 76 ± 8 g in 5 wks as compared to 123 ± 15 g in the control group. The discrepancy with previous work may be explained by the concurrent observation that with our shiftwork protocol rats did not adjust their between-work circadian activity pattern. They maintained a normal level of activity during the "off-work" periods. In the control experiment, rats were kept active during the dark period, normally dominated by activity. This demonstrated that forced activity, per se, did not affect body-weight gain (mean ± SEM: 85 ± 11 g over 5 wks as compared to 84 ± 11 g in the control group). Rats were trained on an instrumental learning paradigm during the fifth week of the protocol. All groups showed equivalent increases in lever pressing from the first (3.8 ± .7) to the sixth (21.3 ± 2.4) session, and needed a similar amount of sessions (5.1 ± .3) to reach a learning criterion (≥ 27 out of 30 lever presses). These results suggest that while on prolonged non-rotating shiftwork, not fully reversing the circadian rhythm might actually be beneficial to prevent body-weight gain and cognitive impairments.

Effect of fasting on young adults who have symptoms of hypoglycemia in the absence of frequent meals

BACKGROUND AND OBJECTIVES

Among otherwise healthy adults, there is a subgroup of individuals who develop symptoms of hypoglycemia during episodes of food restriction. The aim of the present study was to investigate whether such individuals develop hypoglycemia or react abnormally in other metabolic aspects during a 24-hour fast.

SUBJECTS AND METHODS

Ninety medical students were asked if they wanted to participate. Sixteen were selected; none dropped out. A 24-hour fast was performed at a hospital ward. Blood samples and questionnaires were taken at eight specific times.

RESULT

During the fast, the sensitive group reported significantly higher scores on 'irritation' and 'shakiness'. However, no hypoglycemia occurred and the lowest detected blood glucose concentration was 3.7 mmol/l. There were no differences between the groups in plasma glucose, cortisol, growth hormone (GH), insulin, beta-hydroxybutyrate (beta-OH) and lactate levels. The blood pressures and heart rates were also similar.

CONCLUSIONS

Adults, despite subjective signs of hypoglycemia, can fast without any metabolic or endocrine derangement.

Prevalence of self-reported symptoms attributed to hypoglycaemia within a general female population of the UK

OBJECTIVE

To investigate the prevalence of symptoms attributed to hypoglycaemia that are reported by a general female population of the UK.

METHOD

A health and well-being questionnaire, including questions relating to symptoms of low blood 'sugar', medical history and anthropometry, was administered by post to 2000 randomly selected women (17-50 years) in Nottinghamshire. To avoid biasing responses, participants were not made aware of the specific focus of the study.

RESULTS

One thousand one hundred and thirty-six women returned the questionnaire (56.8% response rate). After exclusions, 37.9% of respondents reported symptoms that they attributed to hypoglycaemia, with a median of four episodes reported per month. A significant variation in the reporting of symptoms was found across body mass index (BMI) categories, with the highest prevalence of symptomatic subjects being found at the lowest BMI range (P<.05).

CONCLUSION

More than a third of women in the UK report experiencing symptoms that they attribute to hypoglycaemia. Body mass index appears to be related to the experiencing of symptoms.

Effects of shift work on autonomic and neuromotor functions in female nurses

Thirty-seven nurses with shift work, working under a rotating three-shift system, and 37 nurses without shift work, having worked during the daytime for one or more years prior to this study, were examined to assess the effects of shift work on cardiac autonomic and neuromotor functions. Their ages ranged from 25 to 58 yr. The electrocardiographic (ECG) R-R interval variability, %LF and %HF (i.e., proportions of sympathetic and parasympathetic activities, respectively), and LF/HF ratio were computed by means of autoregressive spectral and component analyses. The %LF and LF/HF ratio were significantly larger in the nurses with shift work than in those without shift work, although there was no significant difference in the heart rate-corrected QT interval on ECG between them. And, hand-ear coordination differed significantly between the nurses with shift work and those without. Despite the presence of potential selection bias, it is suggested that shift work in nurses may cause not only a long-term sympathodominant state but also some neuromotor impairment.

Mental Health Status, Shift Work, and Occupational Accidents among Hospital Nurses in Japan

A questionnaire survey was conducted with questions from the 12-item General Health Questionnaire, among others, targeting 4,407 nurses in 8 general hospitals in Japan, in the hope of improving the work environment of nurses and to provide data that will allow a discussion of the measures necessary for preventing medical errors, thus improving occupational health. For each type of accident, the percentage of those who had made medical errors was significantly higher for the "mentally in poor health" group than for the "mentally in good health" group (p<0.0001). The percentage of nurses in the "mentally in good health" and "mentally in poor health" groups who had experienced occupational accidents over the past 12 months (i.e., whether they were "with errors" or "without errors") was calculated for each of the following four types of medical accident: (1) drug-administration errors, (2) incorrect operation of medical equipment, (3) errors in patient identification, and (4) needlestick injuries. For each type of accident, the percentage of those who had made medical errors was significantly higher for the "mentally in poor health" group than for the "mentally in good health" group (p<0.0001). Multiple logistic regression analyses revealed significant associations between experience of medical errors in the past 12 months and being mentally in poor health, with night or irregular shift work, and age.