Somatic symptoms and psychological characteristics associated with insomnia in postmenopausal women

Abstract

Objective

The aim of the study was to assess the association of sleep disturbance with psychological characteristics, somatic symptoms and previously identified risk factors.

Methods

Data were from 148,938 postmenopausal women enrolled in The Women’s Health Initiative who provided cross-sectional information about psychological characteristics, somatic symptoms and the character of their sleep. Overall sleep quality was based on the Women’s Health Initiative Insomnia Rating Scale (WHI IRS), a measure that assessed five types of sleep disturbance.

Results

Three factors accounted for nearly 20% of the variation in the WHI IRS: a scale for somatic symptoms, daytime restlessness and either depression or emotional well-being. Other independently associated factors were night sweats, pain and worry about expressing anger. Several factors that had been linked to sleep disturbance in other studies were found to have at most a weak independent association in this analysis. These included income, education, marital status, activity level, obesity level, hot flashes, coffee drinking and smoking.

Conclusion

Factors strongly associated with sleep disturbance in this study deserve further evaluation to determine the reasons for the association and whether the associations suggest possible treatments for sleep disturbance.

Introduction

Sleep disturbances are characterised by difficulties falling asleep, waking during the night, staying asleep, waking early, getting back to sleep and non-restorative sleep that cause daytime impairment or distress [1]. Epidemiological studies have found that a third of the general population have sleep disturbances and that disturbed sleep contributes to accidents, cognitive and social dysfunction and impaired physical and psychological health [2].

Sleep problems are affected by both predisposing and precipitating factors [3]. Chief among the predisposing factors are worry, hyperarousal and poor coping. Precipitating factors are most commonly stressful life circumstances [4], [5]. Large-scale epidemiological studies are often unable to measure these factors directly, but they may measure other related characteristics. Factors that have been found to be associated with insomnia include demographics (age [6], [7], [8], [9], [10], race, marital status [11] and socioeconomic status [12], [13], [14]), health [15], [16], health risk (acute or chronic stress [8], [17], [18], [19], [20], inactive lifestyle, obesity [8], [21], [22], [23], [24], caffeine, nicotine [25], [26], [27], [28], [29] and alcohol [30], [31]) psychiatric (mood [14], [23], [32] and anxiety), psychological (poor social functioning [33], [34], anger/hostility [35], inability to express anger [36], discontent [37], somatic and psychological [38]) and somatic symptoms (pain [23], [39], [40], [41], [42], vasomotor symptoms [43], [44], [45], [46], [47], [48] and somatic symptom inventory [49]).

Perhaps the most important risk factors for sleep disturbance are psychiatric disorders [1], [2]. According to a 2008 article in the American Journal of Psychiatry, the strongest risk factor for insomnia is concurrent depressive symptoms [50]. In another article, it was reported that approximately half of the patients with insomnia have a primary psychiatric disorder, most often depression or anxiety [51].

The National Institutes of Health (NIH) State of the Science conference called for the testing of risk factors for insomnia using validated instruments with known psychometric properties, ease of administration and cross-cultural applicability. The present study uses a large epidemiological database to examine the independence and relative strength of psychological and somatic symptoms for different types of sleep disturbance.