Association between depressive symptoms and morningness-eveningness, sleep duration and rotating shift work in Japanese nurses

<p>Higher depressive symptoms have been reported in rotating shift workers compared with day workers. Depressive symptoms in adults who do not engage in night work have also been shown to be associated with chronotype and sleep duration. This study examines associations between depressive symptoms, morningness-eveningness (i.e. the degree to which people prefer to be active in the morning or the evening), sleep duration and rotating shift work. Japanese nurses (1252 day workers and 1780 rotating shift workers, aged 20–59) were studied using a self-administered questionnaire. The questionnaire covered depressive symptoms, morningness-eveningness, sleep habits and demographic characteristics of the participants. The Center for Epidemiologic Studies Depression Scale (CES-D) was used to determine the levels of depressive symptoms. A Japanese version of the Morningness-Eveningness Questionnaire (MEQ) was used to measure morningness-eveningness. The CES-D score of shift workers was significantly (<i>p</i> < 0.05) higher than that of day workers. The MEQ score was significantly (<i>p</i> < 0.05) lower (i.e. greater eveningness) in shift workers than in day workers. Sleep duration on the day shift was significantly (<i>p</i> < 0.05) shorter in shift workers than in day workers. Simple linear regression revealed that the MEQ score, sleep duration on the day shift and current work shift (i.e. rotating shift work) were significantly (<i>p</i> < 0.05) associated with the CES-D score. Multivariate linear regression indicated that greater eveningness and shorter sleep duration were independently associated with higher CES-D scores, while rotating shift work was not. These associations between the MEQ score, the sleep duration and the CES-D score were also confirmed in both day workers and shift workers when the groups were analyzed separately. These results suggest that greater eveningness and shorter sleep duration on the day shift were independently associated with higher levels of depressive symptoms, which may explain associations between rotating shift workers and depressive symptoms. These findings have important implications for the development of novel strategies for preventing poor mental health in day workers and rotating shift workers.</p

Association of habitual dietary intake with morningness-eveningness and rotating shift work in Japanese female nurses

<p>Rotating shift workers are associated with imbalanced dietary intakes. Rotating shift workers and dietary intakes in adults who do not engage in night work have also been shown to be associated with chronotype. However, no studies have examined associations between morningness-eveningness (i.e., the degree to which people prefer to be active in the morning or the evening), rotating shift work and dietary intakes. Therefore, our first purpose was to elucidate the association between morningness-eveningness and habitual food group intakes in rotating shift workers. The second purpose was to elucidate the association of morningness-eveningness and rotating shift work with food group intakes, considering habitual sleep durations. Japanese nurses (1095 day workers and 1464 rotating shift workers) were studied using a self-administered questionnaire. The questionnaire covered habitual dietary intakes, morningness-eveningness and demographic characteristics of the participants. A Japanese version of the Morningness-Eveningness Questionnaire (MEQ) was used to measure self-rated morningness-eveningness. Dietary intakes over the previous 1 month were evaluated using a semi-quantitative food frequency questionnaire. Intakes of pulses, green/yellow vegetables, white vegetables, fruits, algae, eggs, confectioneries/savory snacks and sugar-sweetened beverages were significantly (<i>p</i> < 0.05) associated with the MEQ score in rotating shift workers. Among these food groups, intakes of green/yellow vegetables, white vegetables, fruits and algae were significantly (<i>p</i> < 0.05) lower in rotating shift workers than in day workers, and intakes of confectioneries/savory snacks and sugar-sweetened beverages were significantly (<i>p</i> < 0.05) higher in rotating shift workers than in day workers. Intakes of these food groups were also significantly (<i>p</i> < 0.05) associated with the MEQ score in day workers. In addition, the MEQ score was significantly (<i>p</i> < 0.05) lower in rotating shift workers than in day workers, indicating greater eveningness among rotating shift workers. Multivariate linear regression revealed that the MEQ scores were significantly (<i>p</i> < 0.05) associated with intakes of these food groups, while rotating shift work was associated only with confectioneries/savory snacks. These results suggest that morningness-eveningness is associated with unbalanced dietary intakes in rotating shift workers as well as day workers, which may partially explain associations between rotating shift work and unfavorable dietary intakes. These findings have important implications for the development of novel strategies for preventing poor health caused by imbalanced dietary intakes in rotating shift workers.</p

The number of the adolescents who sought help for psychological distress according to bullying status^a and sources of help.

<p><i>Note</i>. The number of students who sought help, divided according to the total number of adolescents, is shown by bullying status. The frequencies of the subjects who sought help are significantly associated with bullying status in the adolescents (^ap<0.001, Kruskal-Wallis test). The frequency is significantly higher among pure victims than among the uninvolved and pure bullies (p<0.001, with Bonferroni test). *Multiple answers.</p><p>The number of the adolescents who sought help for psychological distress according to bullying status^a and sources of help.</p

The relations between breakfast time, the ratio of energy intake at dinner to total energy intake (E%), and total energy intake and the acrophases of HF nu and LF/HF according to data based on time since awakening.

<p>Pearson correlation coefficients are presented.</p

Frequencies of suicidal feelings by bullying status in middle(-late) adolescents.

<p><i>Note</i>. Suicidal feelings are significantly associated with bullying status in middle(-late) adolescents (^b<i>p</i><0.001, Kruskal-Wallis test). Severity of suicidal feelings is significantly higher in those bullied (pure victims and bully-victims) than in the uninvolved and pure bullies (^c<i>p</i><0.001, Bonferroni post-hoc test), and the severity in pure bullies is significantly higher than in the uninvolved (^d<i>p</i><0.001, Bonferroni post-hoc test) in middle(-late) adolescents. (The total number of subjects is less than the number of subjects analyzed, due to missing data for suicidal feelings or bullying status.)</p><p>Frequencies of suicidal feelings by bullying status in middle(-late) adolescents.</p

Interactive effects of suicidal feelings and bullying status on help-seeking for psychological distress in middle(-late) adolescents.

<p><i>Note</i>. Odds ratio for seeking help (adjusted for gender and age); 95% CI = 95% confidence interval; mild  =  having mild suicidal feelings; serious  =  having serious suicidal feelings. Reference  =  having no suicidal feelings. In each section, subjects with missing data were excluded from the statistical analyses. *: <i>p</i><0.05; **: <i>p</i><0.01; ***: <i>p</i><0.001.</p

Effects of suicidal feelings on help-seeking for psychological distress by source of the help, in pure victims.

<p>Note. Odds ratio for seeking help from the source (adjusted for gender and age); 95% CI = 95% confidence interval; mild  =  having mild suicidal feelings; serious  =  having serious suicidal feelings. Reference  =  having no suicidal feelings. *: p<0.05; **: p<0.01.</p

Ensemble-averaged step counts and heart rate variability variables during the day shift over 24 h.

<p>Values are mean ± SE. Ensemble-averaged fitted curves by using single cosinor analysis for early eaters (black line) and late eaters (red line) depending on breakfast timings according to time since awakening are also depicted. Data are double-plotted to better visualize rhythmicity. HF nu, the ratio of high frequency (HF: >0.15 Hz) power to total power (>0.04 Hz); LF/HF, the ratio of low frequency (LF: 0.04–0.15 Hz) power to HF power.</p

General characteristic of subjects dichotomized into early eaters and late eaters depending on breakfast timing (median: 30 min).

<p>Values are shown as mean ± SD.</p><p>BMI, body mass index; RRI, R-R interval; HF nu, the ratio of high frequency (HF: >0.15 Hz) power to total power (>0.04 Hz); LF/HF, the ratio of low frequency (LF: 0.04–0.15 Hz) power to HF power.</p><p>*Significantly different between the groups (p<0.05).</p>†<p>Non-paired t test;</p>‡<p>Mann-Whitney U test;</p>§<p>Chi-squared test.</p>¶<p>Time since awakening.</p>a<p>The ratio of energy intake to total energy intake (E%).</p><p>General characteristic of subjects dichotomized into early eaters and late eaters depending on breakfast timing (median: 30 min).</p

Pearson correlation coefficients for acrophases of HRV variables.

<p>*p<0.05.</p>¶<p>Time since awakening.</p><p>Pearson correlation coefficients for acrophases of HRV variables.</p