CROSS-SECTIONAL SURVEY ON RISK FACTORS FOR INSOMNIA IN JAPANESE FEMALE HOSPITAL NURSES WORKING RAPIDLY ROTATING SHIFT SYSTEMS

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1 J. Human Ergol., 30: , 2001 CROSS-SECTIONAL SURVEY ON RISK FACTORS FOR INSOMNIA IN JAPANESE FEMALE HOSPITAL NURSES WORKING RAPIDLY ROTATING SHIFT SYSTEMS Takayuki KAGEYAMA, Noriko NISHIKIDO, Toshio KOBAYASHI, Junko OGA and Mieko KAWASHIMA Oita University of Nursing and Health Science, Oita, JapanSt. Lucas College of Nursing, Tokyo, JapanYmmaguchi Prefectural University, Yamaguchi, Japan A cross-sectional survey was carried out for the purpose of examining the association of work stress with insomnia among nurses working rotating shift systems. A self-administered questionnaire on sleep and mental health was distributed to 875 nurses at five hospitals in Japan. Out of the data from 785 (89.7%) respondents, those from 555 women engaged in rapidly and irregularly rotating shift systems as full-time nurses were examined. The prevalence of insomnia (29.2%) was three to four times higher than that in the general population. Among the insomniacs, 23% were current users of medically prescribed hypnotics. Multiple logistic analysis revealed that being 24 or less years old, working three or less night shifts per month, having six or less non-working days per month, receiving less support from colleagues and superiors, and taking care of severely ill patients were independent risk factors for insomnia. The number of hours of a night shift was found not associated with insomnia, taking the above variables into account. These results suggest that at least three factors, i.e., 1) young nurses not adapted to shiftwork, 2) the nurses requiring to remedy sleep deficits on non-working days, and 3) the work stress partly characteristic of nurses, have an adverse influence on their sleep. Introduction Sleep problems are frequent in shiftworkers (SCOTT and LADOU, 1990; SIEBENALER and MCGOVERN,1991; RIBERT and DERRIENNIC,1999; MARQULE and FORET,1999) including nurses (ESTRYN-BEHAR et al., 1990; ESCRIBA et al., 1992). Psychosocial stress also causes sleep problems in workers (JACQUINET-SALORD et al., 1993; TACHIBANA et al., 1996). Although the job of a hospital nurse is a stressful one (MASLACH and JACKSON, 1981; MORI and KAGEYAMA, 1995), only a few reports on the relationship between work stress and insomnia among them are available (ESTRYN-BEHAR et al., 1990; KANDOLIN, 1993). We therefore carried out a cross-sectional survey on this relationship among female hospital nurses in Japan. Subjects and methods A self-administered questionnaire on sleep, work stress, and mental health was distributed to 875 nurses at rive hospitals in Japan, and 785 (89.7%) responded anonymously. In the present study, however, the data from 555 women engaged in rapidly and irregularly rotating shiftsystems as full-time nurses were analyzed (Table 1). Among these five hospitals, two were public hospitals and three were private ones. One public hospital and one private hospital were psychiatric hospitals, and the rest were general hospitals. The nurses in the private psychiatric hospital had a 16-h night shift, while the nurses in the other hospitals had an 8-hour night shift. All of them usually worked 40 hours/week. Insomnia was diagnosed according to the criteria used in a previous study (KAGEYAMA et al., 1997). The first criterion for insomnia is the presence of a subjective sleep-related problem. The second criterion is the presence of any combination of the following four symptoms: difficulty in

2 150 T. KAGEYAMA et al. falling asleep, intermittent waking, premature early waking, and a feeling of light overnight sleep. These symptoms meet the criterion when they occur once or more times per week, and have persisted for at least one month. The third criterion is the presence of one or more of the following aftereffects of sleep disruption: "lethargy", "dozing or napping", "inefficiency at work", "tardiness", "error prone particularly at work" or "overly sleepy". Chronic job stress perceived by the subjects was assessed by means of a 20-item questionnaire developed by NISF IKIDO et al. (2000) and the modified version of the two scales proposed by MORI and KAGEYAMA (1995). The former provides six scales for general working conditions (workload mental workload, problem in personal relationships, reward from work (job satisfaction), support from colleagues and superiors, and job control (job decision latitude)). The latter provides the scales for severity of patients' illness and difficulty in patient-nurse relationship, which are proper stressors to hospital nurses. The reliability and validity of these scales were previously reported (NISF IKIDO et al., 2000; KAGEYAMA et al., 2001a; KAGEYAMA et al., 2001b). The number of major life events within the last six months was counted using a previously reported method (KAGEYAMA et al., 1997). The association of demographic variables and working conditions with insomnia was examined by multiple logistic analysis, using the SAS program (SAS INSTITUTE, 1990). Results The prevalence of insomnia was 29.2% while that of difficulty in falling asleep, intermittent waking, premature early waking, and a feeling of light overnight sleep was 23.5%, 11.9%, 9.8%, and 15.8%, respectively. Table 1. Prevalence of insomnia. NS, not significant.

3 Cross tabulations of insomnia with demographic variables, health status and working schedule are shown in Table 1. Insomnia was frequent in those who had six or less non-working days per month within the last three months. Compared with non-insomniacs, the insomniacs experienced more demanding jobs, more stressful personal relationships, less support from coworkers, less reward from work, and more severely ill patients (Table 2). The prevalence of the use of medically prescribed hypnotics was 9.7%. This rate was higher in the insomniacs than in the non-insomniacs (Table 3). Multiple logistic analysis (Table 4) revealed that being 24 or less years old, having three or less night shifts per month within the last three months, having six or less non-working days per 151 Table 2. Work stress scores in insomniacs and non-insomniacs. Mean (SE). 1)Difference between insomniacs and noninsomniacs (F-test); **P<0.01, *P<0.05. Table 3. Prevalence of the use of medically prescribed hypnotics. Chit=51.6 (df=2), P< Table 4. Multiple logistic analysis for insomnia. 1) These two scores were assumed to be continuous variables 2) Other variables were assumed to be categorical variables. 3) The underline indicates a reference category..

4 152 T. KAGEYAMA et al, month within the last three months, receiving less support from colleagues and superiors, and taking care of more severely ill patients were independently associated with insomnia. Taking these risk factors into account, marital status, having a young child, undergoing medical treatment, current smoking status, alcohol consumption, recent major life events, working at any of the five hospitals, or other work stress scores were not associated with insomnia. Discussion The prevalence of insomnia in the subjects (Table 1) was three to four times higher than that in the general population of the same gender and age (KAGEYAMA et al., 1997), in agreement with previous reports on sleep disorders among shiftworkers (RIBERT and DERRIENNIC, 1999; MARQULE and FORET, 1999; ESTRYN-BEHAR et al., 1990; ESCRIBA et al., 1992). It also agrees with reports on the general population (KAGEYAMA et al., 1997) that difficulty in falling asleep and light overnight sleep are relatively frequent among the subtypes of insomnia. Use of medically prescribed hypnotics was frequent among the insomniacs (Table 3), in agreement with a previous report on the general women (KAGEYAMA et al., 1998) and young nurses (OHIDA et al., 2001). It should also be noted that the prevalence of use of hypnotics among the subjects was three to ten times higher than that in the general population with the same gender and age regardless of whether they were insomniacs or not (KAGEYAMA et al., 1998). Hospital nurses may tend to ask physicians, who are their coworkers, to prescribe hypnotics without considering side effects or the potential to become dependent on them. Multivariate analysis of insomnia (Table 4) provided interesting information, which was not shown by single correlations (Tables 1 and 2). It was reported that insomnia in the general women aged years was rare (KAGEYAMA et al., 1997; OHIDA et al., 2001), and that older shiftworkers were particularly at an increased risk for sleep problems (SIEBENALER and MCGOVERN,1991). In the present study, however, subjects 24 or less years old were at the highest risk for insomnia. Some possible reasons for this are as follows. a) It is possible that young nurses may have not adapted well to rapidly and irregularly rotating shift systems. b) In spite of the significant correlation of the mental workload score with insomnia (Table 2), this score was not associated with insomnia in the results of multivariate analysis (Table 4), because of its inverse correlation with age (data not shown). Taking these results into consideration, young nurses who have not gotten used to their job may face difficulty in completing their job, and this work stress in turn affects their sleep adversely. c) It was reported that the nurses in rotating shift systems were at a high risk of early retirement (NIEDHAMMER et al., 1994). It is therefore possible that the number of middle-aged nurses who have difficulty in adapting to a rotating shift system is small since those who cannot adapt to the work retire before reaching middle age. Most of the subjects in the present study are expected to have night shifts four to eight times per month. If the frequency of night shifts for a subject is less than the above, this means that she chooses to do so for some special reasons such as health problems, care for a family member, and sleep problems. This also means that other nurses are forced to have more night shifts than usual because a certain number of staff members is always required at night. The high risk for insomnia among the subjects with less frequent night shifts is probably related to the above special reasons for avoiding night shifts. On the other hand, frequent night shifts are not associated with insomnia, probably because the subjects who are well adapted to night shifts or who wish to work at night for economic reasons tend to choose more night shifts than expected. The risk for insomnia is also high among the subjects with an extraordinarily less number of days off. This indicates the need for a sufficient number of days off, which also means sufficiently long intervals between work shifts, for the subjects to remedy sleep deficits and to reset their circadian rhythms, as pointed out by previous researchers (SIEBENALER and MCGOVERN,1991; KURUMATANI et al., 1994; MOREHOUSE 1995). In other words, this suggests the need for a sufficient number of personnel at the work site. The above subjects probably had to work frequently

5 to make up for the absence of their coworkers who had taken extra days off. These coworkers, however, might not take the extra days off for reasons related to their sleep or health. This may be the reason why having many days off is not associated with the increased risk for insomnia. The work stress of the subjects is characterized by high demand, high control, and high reward in comparison with the general white-collar workers in Japan (KAGEYAMA et al. 2001a). However, these characteristics of work stress are not associated with insomnia. On the other hand, having severely ill patients and receiving less support from coworkers are independent risk factors for insomnia, in agreement with previous reports that psychological workload is linked with the quality of sleep among workers (URPONEN et al., 1988; JACQUINET-SALORD et al., 1993). Having severely ill patients is a characteristic stressor for hospital nurses. It should also be noted that the severity of patients' illness score does not correlate with age and that it has only weak correlation with the mental workload score (data not shown). The association of social support with insomnia agrees with the results of a recent study on electrical equipment manufacturing shiftworkers (NAKAFA et al., 2001). In the present study, however, details of the support from coworkers were not investigated. There is a moderate correlation of the support from colleagues and superiors score with the reward from work score (data are shown), suggesting that supportive coworkers appreciate the value of the subjects' work. The presence of such coworkers may also contribute to the management of personal time schedules. These speculations should be confirmed in a future study. It was reported that undergoing medical treatment, recent life events, having children six or less years old, sleep apnea-like symptoms, and marital status are associated with insomnia in the general women (KAGEYAMA et al., 1997; DOl et al., 2000). In the present study, however, these variables are not associated with insomnia, probably because of the "healthy workers" effect. Namely, nurses with severe sleep problems due to these reasons may tend to stop working as a full-time nurse in a rotating shift system. When the working conditions shown in Table 4 were taken into account, it was found that there was no difference in the risk for insomnia among the five hospitals, suggesting that the length of night shift or the difference between two- and three-shift systems was not associated with insomnia. This agrees with the claim that the work-related problems in 16-h night shift nurses may not be much greater than those in 8-h evening/night shift nurses, as long as appropriate countermeasures are taken (TAKAHASHI et al., 1999). The results in the present study suggest that at least three factors, i.e., 1) that young nurses are not adapted to shiftwork, 2) that the nurses need to remedy sleep deficits on non-working days, and 3) the work stress which is partly characteristic to nurses, have an adverse influence on their sleep. The countermeasures for sleep problems among hospital nurses in rapidly and irregularly rotating shift systems should include not only consideration of time schedules but also the management of work stress, including the mental and technical support given to them. 153 Acknowledgement This study was partially supported by a Grant-in-Aid for Scientific Research (No ) from the Ministry of Education, Sports, Sciences and Technology in Japan. References DOI, Y., MINOWA, M., OKAWA, M. and UCHIYAMA, M. (2000) Prevalence of sleep disturbance and hypnotics medication use in relation to sociodemographic factors in the general Japanese adult population. J. Epidemiol., 10: ESCRIBA, V., PEREZ-HOVOS, S. and BOLUMAR, F. (1992) Shiftwork: its impact on the length and quality of sleep among nurses of the Valencian region in Spain. Int. Arch. Occup. Environ. Health, 64: ESTRYN-BEHAR, M., KAMINSKI. M., PEIGNE, E. et al. (1990) Stress at work and mental health status among female hospital workers. Br. J. Ind. Med., 47:

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