Prospective study of predictors and consequences of insomnia: personality, lifestyle, mental health, and work-related stressors

Highlights

• Languidity predicted increased symptoms of insomnia over time.

• Anxiety and depression predicted increased symptoms of insomnia over time.

• Bullying and negative spillover predicted increased symptoms of insomnia over time.

• Morningness and positive spillover predicted less symptoms of insomnia over time.

• Insomnia emerged as a precursor for anxiety, but not for depression.

Abstract

Objective

To prospectively investigate the reciprocal relationships between personality traits, lifestyle factors, mental health, sleepiness, and work-related stressors against insomnia.

Methods

A total of 799 Norwegian shift-working nurses (mean age 33.2 years, 90% female) participated in this prospective cohort study. They were assessed on self-report instruments (Bergen Insomnia Scale, Diurnal Type Scale, Hospital Anxiety and Depression Scale, Negative Acts Questionnaire-Revised, Work–Family Interface Scale, among others) in 2008/2009 (wave 1) and 2011 (wave 3). Structural equation modeling was employed to investigate the bidirectional relationship between a wide range of individual and work-related variables and insomnia.

Results

Languidity (β = 0.18***), anxiety (β = 0.11**), depression (β = 0.14***), exposure to bullying behavior (β = 0.08*), and negative spillover between work and family life (work to family, β = 0.08*; family to work, β = 0.07*) predicted increased symptoms of insomnia over time. Morningness (β = −0.09*) and positive spillover from work to family (β = −0.11**) predicted less symptoms of insomnia over time. No support was found for night work as a predictor of increased insomnia. Insomnia was a precursor for anxiety (β = 0.11**), but not for depression (*p <0.05, **p <0.01, ***p <0.001).

Conclusion

The data suggested that insomnia more often emerges as a consequence of individual and work-related factors than as a precursor to them. The scope of factors causing insomnia, and factors protecting against it, should be further investigated. Insomnia should be considered in prediction models for mental illnesses and as an outcome of adverse work-related experiences.

Introduction

Insomnia is a sleep disorder characterized by difficulties initiating or maintaining sleep, which impair daytime functioning [1]. The reported prevalence of insomnia varies from 2% to about 48%, depending on the stringency of definitions and operationalization of the construct [2], [3]. Trend studies have pointed to a rising occurrence of insomnia in the general adult population over the past decades [4], [5], [6], [7], [8], [9]. This may be related to an aging population and increase in being overweight. Increased use of shift work and increased job-related stress may be other important predictors for the rising occurrence of insomnia [4]. In addition, increased use of electronic devices at bedtime may hamper sleep [10]. Finally, increased awareness of the significance of sleep may have spurred the report of sleep problems [11]. Health problems related to insomnia include a range of medical conditions such as: heart disease, hypertension, neurological disease, gastrointestinal problems, cancer, and diabetes, among others [12], [13], [14], [15]. More inextricably linked to insomnia, however, are mental health conditions such as anxiety and depression [16], [17]. Anxiety and stressful life events are also often seen as precursors to sleep difficulties, whereas persistent insomnia is typically seen as a risk factor for depression [18].

Stress and prolonged arousal are key features that may cause sleep difficulties, which is a relationship believed to be mediated by worry and intrusive or repetitive thoughts [19], [20]. One such highly intrusive stressor is exposure to bullying behaviors in the work place; this is defined as the persistent exposure to negative actions from others in a situation or at an intensity that the targeted employee finds it difficult to defend against [21]. Exposure to bullying behavior leads to psychological distress [22] and has been found to predict subsequent sleep difficulties [23], [24], with a call for more studies on the relationship between bullying and sleep difficulties [25].

Another important stressor in contemporary work-life is the challenge of combining work and family life, where too much strain and worry in one domain may spill over to the other in a cyclic process that leads to deficient recovery and poor sleep quality [26]. Work-related strain may also be increasing due to a growing number of 24-hour services and businesses. In order to extend operating hours, these businesses need to organize the staffing through shift work, which has well-known detrimental effects on the workers' health and sleep [27], [28]. However, some people have the ability to adapt to shift work without substantial detrimental effects. Some of the characteristics associated with higher shift work tolerance include low scores on the personality trait ‘morningness’, high scores on flexibility, and low scores on languidity [29]. These three personality characteristics describe different aspects that are related to how the individual relates to the act of sleeping. Morningness refers to individual preferences of timing for sleep and active periods during the 24-hour day [30]; flexibility refers to individual differences in capacity to sleep at odd times [31]; and languidity describes differences in the ability to withstand and overcome drowsiness upon losing sleep [31]. Although these traits are directly related to the individual's sleep and wakefulness, there are few studies that have looked at whether they predict the development of insomnia over time.

Much is known about the precursors of insomnia, but the majority of studies are still cross-sectional, which precludes inferences about directionality [26], [32]. Although an increasing number of studies have used longitudinal designs over the past 15 years, they have tended to focus on only a few variables as predictors of insomnia [16], [23], [33], and very few have studied the potential bidirectional relationship between these variables and insomnia [16], [17], [23].

Therefore, the purpose of the current study was to employ a prospective design to investigate the reciprocal relationship between a wide range of individual and work-related variables against insomnia (personality traits, lifestyle factors, mental health, sleepiness, and work-related stressors).