Original ArticleChronic sleep difficulties in non-depressed young women: a longitudinal population-based investigation
Introduction
Numerous epidemiological studies have estimated that about a third of the adult population report some dissatisfaction with their sleep. Insomnia, or difficulties with sleep onset, maintenance or early morning awakenings that cause significant daytime impairment and distress, has an estimated overall prevalence of 5–10% of the general population [1], [2], [3]. The prevalence increases with age, and it is twice as common in women as in men [2], [4]. The course and prognosis of insomnia symptoms are highly variable. Sleep difficulties are often situational and transitory, lasting only a few weeks. In some cases, the sleep problems remain after the initial causal factor is removed. However, in many cases, individuals may be predisposed to develop sleep difficulties because of personality traits or co-morbid conditions, often making the disorder chronic or recurrent over time. It is estimated that around 50% of those who experience an episode of insomnia will continue to have symptoms up to one year later [5]. Chronic insomnia is associated with an increased risk of psychopathology, including depression and anxiety [6], [7] and other negative health outcomes [8], [9].
Despite being a prevalent condition, there are limited data on the natural history of insomnia [10], [11], [12], particularly in those who are most vulnerable to the condition [13]. A number of studies have examined the trajectory of persistent insomnia in community cohorts, with prevalence rates of between 5% and 20%, depending on how insomnia was defined [5]. However, many of these studies are limited by short follow-up periods or retrospective data-analysis methods. In a short-term study, 69% of people who reported insomnia symptoms at baseline still had insomnia at one year follow-up, and the persistence of insomnia increased by 10% for each 10-year increase in age [14]. A study by Morin assessed the trajectory of insomnia in a community sample of >380 individuals over a three-year period [10]. Insomnia persisted in 46% of individuals across the 3 years, and it was more common in women and those with more severe symptoms at baseline. Remission rate was >50%; however, over half of these people eventually relapsed. In a Swedish community sample of 2602 men aged 30–69 years, those who had insomnia at baseline had a 6.45 times increased risk of having insomnia 10 years later [15]. Only 56% of the men who reported insomnia at baseline did not report insomnia at follow-up. These studies suggest that insomnia is a persistent condition, associated with low remission rates and high relapse rates.
Insomnia is becoming increasingly prevalent in young adults [7]. However, there are limited data regarding whether insomnia also persists in this age group. In a longitudinal study spanning 20 years, Buysse and colleagues assessed the chronicity of insomnia and co-morbid symptoms in 591 young adults [5]. The prevalence of insomnia increased slightly from the ages of 20–40 years, tended to persist within individuals and was higher in women. Longitudinal analysis indicated that pure insomnia (ie not co-morbid with other psychopathologies) was associated with future episodes of insomnia, with odds ratios (ORs) of between 2.5 and 4.0 across successive surveys. Whether the persistence of insomnia symptoms in women specifically is higher than this was not examined. Chronic insomnia increases the risk of a range of health issues and psychopathologies, and young women may be at a particularly high risk of depression and anxiety if sleep issues are not addressed [7]. Given the higher prevalence of insomnia in women, and its association with a number of negative health outcomes [8], [9], it is important to understand the persistence of the disorder in this population. It is also not well documented whether insomnia not associated with another psychiatric condition also persists over time.
In clinical practice, insomnia is under-recognized and under-treated. Contributing factors are the general community's lack of knowledge regarding the treatment options for sleep and/or individuals not seeking treatment. Community surveys report that only a third of people with sleep problems sought help [4], [16]. An Australian study found that 11% of the adult sample reported seeking help for sleep problems, but only 6% of those under 25 years of age reported seeking help [16]. This figure is higher in samples from primary care, with between 31% and 52% of respondents reporting that they have discussed their sleep with their physician [17], [18], [19]. Primary determinants of help seeking for insomnia have been identified, and they include being female, more severe insomnia, greater daytime symptoms, greater number of co-morbid conditions, and lower socio-economic status [4], [16], [18]. Some studies report that older age is associated with increased help seeking [16], whereas other studies in primary-care patients have found that younger people tend to seek more help for their sleep [18]. Understanding more about help-seeking behaviour for sleep difficulties, and the level of satisfaction with the outcomes of such help seeking, are important steps towards improved treatment and education about sleep problems in the community.
The aim of this study was to examine whether sleep difficulties persist over a 9-year time period in a large community sample of young women who, at baseline, do not have depression or anxiety. A secondary aim was to determine help-seeking behaviour in young women over time, the corresponding levels of satisfaction with the help sought and how these variables may interact with the level of sleep difficulty.
Section snippets
Data collection
The current study used data from the Australian Longitudinal Study on Women's Health (ALSWH). This longitudinal cohort study is designed to track the health of women over a period of at least 20 years. The ALSWH sample was drawn from the database of the Health Insurance Commission, the universal provider of basic health insurance, which involves all women in Australia. The participants in the survey are broadly representative of the Australian population; however, women from rural and remote
Response rates and sample characteristics
The survey response rates were 68.0%, 63.7%, 64.2% and 57.6% for the years 2000, 2003, 2006, and 2009, respectively. The majority of the respondents in 2000 were not married, had tertiary education and had a professional or clerical/service worker occupation [7].
The prevalence figures for sleep difficulties for all women who responded at each survey are displayed in Table 1. Sleep difficulties ‘often’ were reported by 10.1% of the sample in 2000, and this prevalence remained steady over the
Discussion
The current study was the first to examine the chronic nature of sleep difficulties in a large community cohort of young women, who, at baseline, did not report depression or anxiety. The key finding of this study was that those women who reported frequent sleep difficulties in 2000 had a 10-fold increased risk of continued sleep problems over the next 9-year period compared with women with no sleep difficulties. Although about a third of these women sought help, less than half were satisfied
Conflict of interest
Drs. Diamond and Sztendur are the directors of ESQUANT Statistical Consulting. None of the authors have any financial conflicts of interest to disclose.
The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.10.1016/j.sleep.2015.05.008.
Acknowledgement
Melinda Jackson was supported by an Australian National Health and Medical Research Council Fellowship (APP1036292).
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Current address: School of Health Sciences, RMIT University, Bundoora, VIC 3083, Australia.