Original ArticlePrevalence and associated factors of DSM-V insomnia in Norway: the Nord-Trøndelag Health Study (HUNT 3)
Introduction
Insomnia has a strong effect on patients’ health-related quality of life [1], and has a substantial economic impact on society [2], [3], [4]. It is also associated with a wide range of physical and mental health problems and found to be a predictor of depression, anxiety, and cardiovascular diseases [5], [6], [7], [8], [9]. Many studies have attempted to assess the prevalence of insomnia in their respective populations. However, the reported prevalence differs widely, from 2% [10] to 48% [11], mainly because of methodological variability [8], [12]. Some of this variation may be due to different definition of insomnia as several studies have used non-standard diagnostic criteria. To our knowledge, no previous study has assessed the prevalence of insomnia in the general population using the recently published DSM-V criteria. Finally, it is surprising that almost all epidemiological studies ignored the influence of non-participants in their insomnia prevalence estimate.
The primary aim of the present large population-based cross-sectional study was to assess the prevalence of insomnia using the DSM-V [13] criteria, adjusting for prevalence data in non-responders. A secondary goal was to analyze the relative influence of age, gender, employment status, body mass index, systolic blood pressure, smoking, alcohol consumption, physical activity, chronic musculoskeletal complaints, anxiety, depression, and levels of self-reported health on insomnia.
Section snippets
Study area
The county of Nord-Trøndelag is one of 19 Norwegian counties, and is located in the central region of Norway. The inhabitants are fairly representative of the Norwegian population, ethnically mainly consisting of Caucasians and lacking any cities with >25,000 inhabitants.
HUNT studies
The entire population of the Nord-Trøndelag County aged ⩾20 years was invited to participate in the Nord-Trøndelag Health Survey (HUNT) conducted in 1984–1986 (HUNT 1), in 1995–1997 (HUNT 2), and in 2006–2008 (HUNT 3). The main
Three-month prevalence of insomnia
A higher prevalence of insomnia was found in women than in men in all age categories of HUNT 3 participants (Table 1). Prevalence of insomnia was highest in the youngest age groups in women, whereas the prevalence of insomnia was nearly constant across age groups in men. The overall age-adjusted prevalence of insomnia was 8.6% (95% CI, 8.3–9.0) in women and 5.5% (95% CI, 5.1–7.8) in men (overall, 7.1%; 95% CI, 6.9–7.4). The sex ratio was 1.6. The prevalence of insomnia symptoms was higher among
Prevalence
In this large-scale population-based cross-sectional study, the prevalence of insomnia changed from 7.1% to 7.9% when adjusting for a higher prevalence of insomnia symptoms among non-participants. Our age-adjusted insomnia prevalence of 7.1% in responders was low compared to the majority of epidemiological studies on this topic, but in accordance with most other studies using DSM inclusion criteria [8], [12], [18], [19], [20], [21], [22], [23], [24]. It should be emphasized that the DSM-V
Conclusion
In this large-scale population-based cross-sectional study using DSM-V criteria for insomnia, the age-adjusted prevalence of insomnia was 7.1% in total (8.6% in women, 5.5% in men). When considering non-participants, the prevalence estimate reached a total of 7.9% (9.4% in women, 6.4% in men). Insomnia was associated with heavily reduced general self-reported health and to several other health-related factors; of these, the association was strongest with depression and anxiety. The inclusion of
Funding sources
None.
Conflict of interest
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.2014.01.018.
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