Tomohide Kubo

• Ph.D
• Senior Researcher at National Institute of Occupational Safety and Health JAPAN

We examined cardiovascular responses during driving and investigated the effects of different break patterns on these responses. Forty-seven males in their 40s and 50s participated, and the protocol included three driving sets with four break patterns. One driving set consisted of 1 hour of city driving and 1 hour of highway driving. The four break...

Background Given that nighttime sleep has more recuperative power than daytime sleep, ensuring the former is important to recovery from work, especially for shift-working nurses. In this 1-month sleep log study, we preliminarily examined how the number of monthly nighttime-sleep opportunities relates to fatigue-related outcomes among shift-working...

Objective This study aimed to prospectively investigate the association between work environment improvements and multiple mental health outcomes in a large sample of Japanese employees. Methods A web-based longitudinal study surveyed 20 000 Japanese employees, 7 970 of whom completed a follow-up after 1 year. Various types of work environment imp...

Daily rest period (DRP) refers to the interval between the end of one workday and the start of the next. This study examined the joint association of DRP and sleep duration with subsequent sick leave among Japanese daytime employees. Participants (n=5,593) were measured for DRP and sleep duration at baseline and for sick leave at 1-year follow-up....

Circadian typology, or "morningness" and "eveningness," is generally assessed using the Morningness-Eveningness Questionnaire (MEQ), a 19-item scale that could be burdensome in large-scale surveys. To overcome this, a 5-item version known as the reduced morningness-eveningness questionnaire (rMEQ), which is sensitive to the assessment of circadian...

Objectives: Several health issues are associated with irregular sleep patterns. However, it is unclear what causes workers to sleep irregularly. The work interval (WI) between the end of one day's working hours and the start of the next day's working hours contains sleep opportunities, and an irregular WI may result in irregular sleep. This study...

Background Exposure to workplace aggression adversely affects workers’ health; however, little is known regarding the impact of specific types of verbal content. Aims We aimed to examine the relationship between exposure to several types of aggressive words at work and the victim’s depressive symptoms and sleep disturbance using text mining. Meth...

The Japanese word Karoshi meaning death due to overwork, has been internationally recognised since it was listed in the Oxford English Dictionary in 2002. Karoshi is also socio-medically defined as death or disorder from overwork-related diseases, such as stroke, myocardial infarction, or acute cardiac failure, which can occur due to aggravated hyp...

Purpose Exercise is considered a strategy to promote mental health among workers. However, the optimal exercise conditions that promote mental health benefits for workers are still unclear. This study examined the cross-sectional associations of weekly exercise time duration, social context of exercise, and exercise motivation levels with the menta...

Objectives This study examined the effects of work-related electronic communication (WREC) during non-working hours in the work from home or office setting on health. Methods The study recruited 98 information technology workers in a 9-day observational study. They recorded work–life events (eg, work style (working mostly from home or the office)...

Mental health problems are prevalent among the working population and must be resolved. We conducted a web-based large-scale study of workers, including a baseline survey and two follow-up surveys, to investigate the associations between self-care behaviors in daily life (e.g., stress coping, sleep, diet, and exercise), work environment improvement...

Introduction Patients with depressive disorder demonstrate rest–activity rhythm disturbances and cognitive function impairment. This study examined the association of individual rest–activity rhythm changes over time with mood symptoms and attention. Methods We recruited 15 adult outpatients with a diagnosis of major depressive disorder from a sin...

This study aimed to examine the joint association of daily rest period (DRP) and sleep duration with occupational stress and sickness absence in Japanese daytime employees. This study utilized a web-based cross-sectional survey conducted in February 2022. The 13,306 participants reported their DRPs and sleep duration. Occupational stress was assess...

The cognitive ability to self-monitor one's current performance is important for hospital nurses to maintain safety and health. However, studies on the effects of rotating shift work on self-monitoring ability are insufficient. We examined the differences in self-monitoring accuracy across shifts in a rotating three-shift system among 30 female war...

Objectives: This study examines the mediating and moderating effects of psychological detachment (PD) based on the stressor-detachment model long term. Methods: Two waves of web-based surveys, 28 months apart, yielded 3,556 responses from Japanese workers. Comparisons between models that included mediating and moderating effects of PD, and rever...

More knowledge is required to determine the optimal shiftwork schedule to reduce the harmful effects of short restart breaks between shifts. This 5-month intervention study aimed to examine the effectiveness of extended restart breaks from 31 h to 55 h after consecutive night shifts by considering the characteristics of the circadian rhythm to miti...

Previous studies among middle-aged and older adults have shown that engagement in exercise with others is more strongly associated with better mental health than engagement in exercise alone. However, the applicability of such findings to workers remains unclear. This study aimed to examine whether 1) engagement in exercise with others and time spe...

This study aimed to explore the background of traumatic events and possible preventive measures among health care workers. We analyzed data from 84 compensated health care workers who experienced traumatic events between 2010 and 2017. We found that about half of the workers had encountered violence, and nearly half were alone at the time of the vi...

A daily rest period (DRP) is a daily inter-work interval that contains sleep opportunity. This study investigates the joint association of DRP and sleep duration with worker health and productivity. A total of 13,306 Japanese daytime workers participated in this web-based cross-sectional survey. Participants reported on their DRPs and sleep duratio...

Objective: During the Coronavirus disease 2019 (COVID-19) pandemic, social isolation and impaired social interaction could be the factors that cause mental health problems. This study investigated the association between conversation time in daily life and mental health among Japanese employees. Methods: In August 2021, a web-based cross-section...

Study Objectives To examine the effect of sleep timing intervention on sleep quality, attention, and sleepiness at work among night shift workers with shift work disorder. Methods We recruited 60 real-life night shift workers through advertisements to participate this cross-over clinical trial. Shift work disorder was confirmed with interview and...

Objectives: This study examined the characteristics of occupational mental disorders among those involved in the transport and postal activities in the trucking industry. Method: We examined 237 out of 3517 cases of occupational mental disorders, compensated between the fiscal years 2010 and 2017. An assessment was made for sex, "life-or-death"...

Objective A sufficient duration of time off after work is necessary to ensure workers’ health. Better quality of off-job time can also facilitate recovery from fatigue, but its quantitative influence is largely unknown. We aimed to examine how off-job time quality (as measured by the frequency of emailing after work), and off-job duration is associ...

Aims To examine coronavirus disease 2019 (COVID-19) pandemic-related work factors for adverse effects on the mental health and whether organisational strategies attenuate these effects. Background COVID-19 pandemic has led to increased work burden and mental health risks for nurses. Methods A total of 1499 Taiwanese full-time nurses completed a w...

The daily rest period (DRP) is the daily inter‐work interval and can include a sleep opportunity, leisure time, and other non‐work time. A longer DRP may allow workers to increase time in bed (TIB) and adjust sleep timing, and that may reduce sleep problems such as short sleep duration, sleep debt, social jetlag, and poor sleep quality. The present...

Purpose We aimed to cross-sectionally investigate how work and sleep conditions could be associated with excessive fatigue symptoms as an early sign of Karoshi (overwork-related cerebrovascular and cardiovascular diseases; CCVDs). Methods We distributed a questionnaire regarding work, sleep, and excessive fatigue symptoms to 5410 truck drivers, as...

The aim of the study was to examine the relationship between sleep problems and objective driving behaviors of short-haul commercial truck drivers in Japan. One hundred and ten male short-haul commercial truck drivers’ sleep duration, sleep quality (Pittsburgh Sleep Quality Index), and frequency of sleepiness at the wheel were measured by survey in...

While a number of work-related events have been proposed as risk factors for depression, a majority of studies have focused only on a few events in a single study. Therefore, we conducted a web-based longitudinal study to comprehensively investigate the impact of various work-related events on depressive symptoms. Ten thousand Japanese workers repr...

: Job automation and associated psychosocial hazards are emerging workplace challenges. This study examined the trends in work conditions and associations with workers’ health over time in jobs with different automation probabilities. We utilized data from six waves of national questionnaire surveys of randomly selected 95,762 employees between 200...

This study aimed to examine the status of depression symptoms and occupational stress factors that triggered these symptoms among workers in medical and welfare industries. Web-based surveys were conducted in 2016 and 2019 among research company survey respondents regarding their work, life and health. This study extracted data for medical services...

Objectives We investigated the association of working hours with occupational injuries in hospital shift work. Methods Registry data of occupational injuries of hospital employees from 11 towns and 6 hospital districts were linked to daily payroll data to obtain working hours for 37 days preceding the first incidence of the injury (N=18 700). A ca...

Objectives: The work interval duration between the end of one workday and the start of the following workday is referred to as the daily rest period (DRP). The present study examined whether DRP – a proxy for sleep opportunity between work shifts – is associated with indicators of sleep debt and social jetlag among daytime workers. Methods: We used...

Objectives: Karoshi problems (overwork-related deaths and disorders caused by cerebrovascular and cardiovascular diseases) still occur in Japan. Truck drivers, who are in one of the riskiest occupations, are reported to show an increased prevalence of hypertension, obesity, hyperlipidemia, and diabetes, which are characteristic of Karoshi. Their h...

This cross-sectional study aimed to explore work and rest conditions associated with overfatigue in truck drivers. A total of 1,911 male truck drivers participated in a questionnaire survey regarding their employment conditions, work habits, rest habits, sleep habits, health status, and subjective fatigue. Compared to local drivers who worked durin...

This study examined the effects of work-related behaviors (checking e-mails and overtime work at home) during off-job time on workers’ sleep quality, fatigue, and functional impairment at work in the context of improving the workplace environment (IWE). A manufacturing company conducted the IWE, and 36 workers participated in surveys conducted one...

A large number of workers worldwide engage in shift work that can have significant influences upon the quality of working life. For most jurisdictions, setting and enforcing appropriate policies, regulations, and rules around shift work is considered essential to (a) prevent potentially negative consequences of shift work and (b) to improve worker...

Background: The European Union's Working Time Directive stipulates recovery periods as "Eleven consecutive hour daily rest periods (DRPs) between working days." In Japan, adopting this regulation has been discussed. Objective: To examine the association between weekday DRPs and recovery from fatigue by conducting a one-month observational study usi...

This study examined the association between health-related risks and sitting time in three different domains covering a worker’s typical life. We investigated the beneficial effect of replacing sitting time with standing/walking time in the workplace using the isotemporal substitution model (ISM). The survey was administered through the Internet. W...

Objectives: This study aimed to describe the sleep quantity, sleep quality, and daily rest periods (DRPs) of Japanese permanent daytime workers. Methods: Information about the usual DRP, sleep quantity, and sleep quality (Japanese version of the Pittsburgh Sleep Quality Index: PSQI-J) of 3867 permanent daytime workers in Japan was gathered throu...

Objective: We aimed to examine the effects of the daily rest period (DRP) on resting blood pressure (BP) and fatigue and determine the optimal DRP for daytime workers. Methods: Fifty-four daytime employees participated in a 1-month observational study. BP was measured thrice at the workplace. Employees underwent a pre- and post-survey to determi...

A daily rest period (DRP; rest taken from daily work during a 24 h period), is essential to work recovery. This study examined DRPs' distribution and association with health outcomes among information technology workers recruited from an internet panel (N = 1,811). Participants completed a web questionnaire examining psychological distress as a pri...

Objectives: This study aimed to develop the Career Anchors Scale among Occupational Health Nurses (CASOHN) and evaluate its reliability and validity. Methods: Scale items were developed through a qualitative inductive analysis of interview data, and items were revised following an examination of content validity by experts and occupational healt...

Objectives: This observational study aimed to determine how 1-year changes in work time control (WTC) have an impact upon objectively measured fatigue and sleep among employees. Methods: Thirty-nine employees were divided into two groups according to whether or not their WTC increased from baseline to 1 year later. Psychomotor vigilance task (PV...

Aim: This study examined the career anchor characteristics that are possessed by Japanese occupational health nurses. Method: Sixteen occupational health nurses participated in the semistructured interview. Data analyses were conducted using descriptive qualitative methods. Results: The data showed the following five categories: practices conc...

The ability to awaken at a predetermined time without an alarm is known as self-awakening. Self-awakening improves morning alertness by eliminating sleep inertia; however, the effects of self-awakening on daytime alertness and alertness that has deteriorated as a result of sleep loss are unknown. The aim of this study was to determine the effects o...

Objectives: The period of leisure is an appropriate time to recover from work-induced fatigue, though some recovery takes place during rest breaks at work. Recently, much attention has been paid to the critical role of leisure activity in recovery. However, the findings relevant to shiftwork nurses who cannot take a day-off regularly are limited....

Background High levels of control over working time and low variability in working hours have been associated with improved health-related outcomes. The potential mechanisms for this association remain unclear.AimsTo examine how work-time control and variability of working times are associated with fatigue recovery, sleep quality, work-life balance...

This study addressed a rarely studied question of self-perceptions of performance and overall functional state during cumulative sleep restriction and the ensuing recovery period. Twenty healthy male volunteers, aged 19-29 years, were divided into a sleep restriction group (n = 13) and a control group (n = 7). On the first 2 nights, the sleep restr...

OBJECTIVE: We examined how change in work time control was associated with sleep and health 1 year later. METHODS: Work time control, sleep, fatigue, recovery, and depression were assessed at baseline (T1) and at follow-up (T2) for 2382 daytime workers. The change in work time control from T1 to T2 was classified into four groups: low to low, low t...

This study was conducted to determine whether extended sleep time during the weekend improves alertness and performance during the subsequent week for workers who are habitually short on sleep time. Daytime employees in the manufacturing industry [38.3, standard deviation (SD) 8.1 years old, mean weekday sleep ≤6 hours] participated in a study that...

We investigated the association between worktime control and fatigue, sleep problems, and depressive symptoms in a sample of daytime and shift workers. A total of 3681 permanent daytime workers and 599 shift workers completed a questionnaire designed to assess the above variables. Worktime control was evaluated in terms of both "control over daily...

Napping is one strategy that may assist night shiftworkers to cope with sleepiness and fatigue. However, one potential disadvantage of napping is that awakening from naps is disturbed by sleep inertia, which has also been found to impair performance and/or mood, transiently. The authors examined the effects of the timing and length of a night-shift...

Increased night work is an important issue because of its implications on workers' health, safety and performance. This study examined the effects of brief hourly exercise as a countermeasure against the adverse effects of night work, especially for workers requiring sustained attention while working in a prolonged sitting posture. During simulated...

The aims of the study were to investigate the systematic classification of subsidiary behaviors during visual display terminal (VDT) work and discuss the interpretation of these behaviors through an interactive model of subsidiary behaviors, work performance and autonomic nerve activity. Twelve university students were instructed to perform continu...

The purpose of this study was to characterize the recovery pattern of sleep following simulated, four successive night shifts in ten healthy men (22.9 + or - 3.2 yr). Poor sleep was defined as sleep efficiency of 80% or lower as determined actigraphically. The results showed that four (rapid, slow, pseudo, and incomplete) patterns of sleep recovery...

Adjustable sit-stand workstations, which are designed to allow workers to sit and stand autonomously while working, were examined to identify the effects on workers' musculoskeletal discomfort, alertness and performance. Twenty-four healthy subjects participated in the study. The subjects were required to do an English transcription task for 150 mi...

The aim of the present study was to reveal characteristic patterns of fatigue feelings on consecutive night shifts by a questionnaire for work-related fatigue feelings "Jikaku-sho shirabe". Ten healthy males (Mean +/- SD: 22.9 +/- 3.2 years old) participated in the experiment. Participants were required to attend the laboratory for nine consecutive...

The study examined how nap length, nap timing and sleep quality affect early morning performance (6:00 to 8:00). Twelve students participated in a simulated nightshift schedule (22:00 to 8:00) where the length and timing of nocturnal naps were manipulated (0:00-1:00, 0:00-2:00, 4:00-5:00 and 4:00-6:00). A performance test battery was administered c...

This study examined the effects of a health education program based on the self- reliance and self-action philosophy and the use of group work methodology on hypercholesterolemia during and after the intervention period. Thirty-two people participated in the study. Measurement values were obtained at the commencement of the intervention (Baseline),...

Nighttime napping is an effective measure to prevent adverse effects due to night shift work. A characteristic of nighttime nap is that it can result in considerably deeper sleep. Several studies have shown that taking nighttime naps suppressed increasing sleepiness, decreasing alertness during the period following awaking from a nap, and prevented...

To examine the effects of the length and timing of nighttime naps on performance and physiological functions, an experimental study was carried out under simulated night shift schedules. Six students were recruited for this study that was composed of 5 experiments. Each experiment involved 3 consecutive days with one night shift (22:00-8:00) follow...