Original ArticleRisk factors for incident chronic insomnia: A general population prospective study
Introduction
Insomnia is the most common sleep disorder, with substantial impact on the individual and the society as a whole. Some of the known consequences of insomnia include poor socio-occupational functioning, increased risk of psychiatric disorders, higher utilization of health care services, and higher risk of motor vehicle accidents [1], [2]. More recent studies indicate that insomnia with objective short sleep duration is associated with significant morbidity and mortality [3], [4], [5], [6]. Therefore, it is crucial to identify the risk factors of insomnia, which may improve prevention and treatment.
The prevalence of insomnia in the general population ranges between 7.5% and 30% [6], [7], [8] and is frequently associated with medical and psychiatric disorders [8], [9], [10], [11], [12], [13]. The nature of the association between chronic insomnia and medical and psychiatric disorders is not established as most of these studies exploring prevalence and risk factors have been cross-sectional. Furthermore, in clinical practice, many patients with chronic insomnia report to have been “light or poor sleepers” even before developing chronic insomnia (ICSD-2); however, no large, general population epidemiological studies have examined this association.
Longitudinal studies are important in establishing the direction of the association between two conditions, i.e., mental health and chronic insomnia. The few longitudinal studies examining the risk factors of incident insomnia were limited by lack of information on medical and psychiatric disorders and certain behavioral factors (e.g., caffeine), small sample size and a relatively short duration of follow-up, or were limited to specific population groups (elderly, men) [14], [15], [16], [17], [18]. Furthermore, none of these studies included objective measures of sleep (i.e., polysomnography) at baseline.
In this study we examined the association of demographics, behavioral factors, psychiatric and medical disorders, MMPI-2 personality traits, and polysomnography with subsequent onset of insomnia 7.5 years after the initial evaluation in a large general population sample of men and women.
Section snippets
Population
The data presented here were collected as part of a population-based study to establish the age distribution of sleep disordered breathing, which used a two-phase protocol in order to recruit participants from various age groups [19], [20]. The study was approved by the University’s Institutional Review Board. In the first phase of the study, a sample of adult men and women (age ⩾ 20 years) was randomly selected from local telephone households in two counties of Central Pennsylvania (Dauphin and
Results
The demographic and behavioral characteristics of the overall study sample, stratified by incident chronic insomnia status, are presented in Table 1. One hundred and thirty-three subjects developed insomnia after an average of 7.5 years of follow-up, reflecting a sampling weight adjusted incidence of 9.3%. Women, young adults (20–35 years), non-whites, and obese individuals had a significantly higher risk of developing insomnia. Moreover, individuals who consumed on average ⩾3 cups of coffee had
Discussion
Our study shows that the complaint of poor sleep and the presence of mental health problems are stronger predictors of incident chronic insomnia compared to physical health problems. Furthermore, neither objective short sleep duration nor sleep apnea significantly predicted incident chronic insomnia.
The incidence of insomnia was similar to the rates in previous studies [7], [14], [16]. Previous studies [16], [17] followed subjects for one year and neither assessed the presence of medical
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: doi:10.1016/j.sleep.2011.11.010.
Acknowledgements
This research was funded in part by the National Institutes of Health Grants RO1 51931 (E.O.B.) and RO1 40916 (E.O.B.). The work was performed at the Sleep Research and Treatment Center at the Penn State University College of Medicine, and the staff is especially commended for their efforts.
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