Elsevier

Sleep Medicine

Volume 13, Issue 4, April 2012, Pages 346-353
Sleep Medicine

Original Article
Risk factors for incident chronic insomnia: A general population prospective study

https://doi.org/10.1016/j.sleep.2011.10.033Get rights and content

Abstract

Objective

The few population-based, prospective studies that have examined risk factors of incident insomnia were limited by small sample size, short follow-up, and lack of data on medical disorders or polysomnography. We prospectively examined the associations between demographics, behavioral factors, psychiatric and medical disorders, and polysomnography with incident chronic insomnia.

Methods

From a random, general population sample of 1741 individuals of the adult Penn State Sleep Cohort, 1395 were followed-up after 7.5 years. Only subjects without chronic insomnia at baseline (n = 1246) were included in this study. Structured medical and psychiatric history, personality testing, and 8-h polysomnography were obtained at baseline. Structured sleep history was obtained at baseline and follow-up.

Results

Incidence of chronic insomnia was 9.3%, with a higher incidence in women (12.9%) than in men (6.2%). Younger age (20–35 years), non-white ethnicity, and obesity increased the risk of chronic insomnia. Poor sleep and mental health were stronger predictors of incident chronic insomnia compared to physical health. Higher scores in MMPI-2, indicating maladaptive personality traits, and excessive use of coffee at baseline predicted incident chronic insomnia. Polysomnographic variables, such as short sleep duration or sleep apnea, did not predict incident chronic insomnia.

Conclusion

Mental health, poor sleep, and obesity, but not sleep apnea, are significant risk factors for incident chronic insomnia. Focusing on these more vulnerable groups and addressing the modifiable risk factors may help reduce the incident of chronic insomnia, a common and chronic sleep disorder associated with significant medical and psychiatric morbidity and mortality.

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.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

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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