[A connection between insomnia and psychiatric disorders in the French general population]

Untreated insomnia often has repercussions on socio-professional or cognitive functioning of insomniacs. In industrialized countries, the prevalence of insomnia ranges between 10% and 48%, depending on the methodology and the measured time interval. However, few studies have examined the relationship between insomnia and mental disorder diagnoses. This epidemiological study on insomnia complaints was conducted on 5 622 subjects representative of the non-institutionalized French population aged 15 years or over. Sixteen interviewers using the Sleep-EVAL expert system performed telephone interviews. Insomnia complaints (defined as difficulty initiating or maintaining sleep, feeling unrefreshed at awakening accompanied by dissatisfaction with sleep quality or quantity, or use of sleep-promoting medication) were observed in 18.6% (95% confidence interval: 17.6% to 19.6%) of the sample. The median duration of insomnia complaints was five years. Regional variations in the prevalence of insomnia complaints were observed in France. In North 2 and Center 4 regions, the prevalence of insomnia complaints was higher compared to the rest of France with a relative risk of 1.4 (95% confidence interval: 1.1-1.6) time superior for the North region and 1.3 (95% CI: 1.0-1.6) for the Center 4 region. The lowest prevalence was registered in the Mediterranean area. In most regions, the prevalence of insomnia complaints was higher in women than in men with the exception of the South and West regions where the prevalence was similar. Subjects with insomnia complaints consulted more frequently compared to the rest of sample with an odds ratio of 3 to 1 [95% CI: 2.8 to 4.1]. Close to 20% of subjects were being treated for a physical disease at the time of the survey; subjects with insomnia complaints being twice more numerous (34.3%) than the rest of the sample (15.9%; p<0.001). To identify the main factors associated with insomnia complaints, socio-demographic and health variables were introduced in a multivariate model. Separated or divorced individuals (OR: 1.6); widowers (OR: 1.5); subjects aged between 45 and 65 years (OR: 1.4) or older than 65 (OR: 1.5); women (OR: 1.3); those with little or no education (OR: 1.4); and subjects living in the North region had higher reported insomnia complaints. Living in the East region (Mediterranean) was a protective factor (OR: 0.6). Furthermore, subjects with vascular diseases (OR: 2.0), musculo-skeletal diseases (OR: 2.0) or cardiac diseases (OR: 1.9) and those who had consulted a physician in the previous six months (OR: 2.7) had higher a probability of insomnia complaints. Subsequently, DSM IV insomnia diagnoses were examined in subjects who complained of insomnia. A diagnosis of primary insomnia was found in 7% of these subjects. A diagnosis of insomnia related to another mental disorder was found in 15.6% of insomnia complainers. A depressive disorder diagnosis was given in 10.8% of cases (mainly a major depressive disorder). This diagnosis was made more often among women and subjects of less than 65 years. An anxiety disorder diagnosis was given for 33.1% of insomnia complainers (an anxiety generalized disorder in about half the cases). About a quarter of insomnia complainers did not receive a diagnosis. This was the case more often for men and the subjects 65 years or older. If demographic and medical factors are relatively well documented at the epidemiological level, it is otherwise for psychiatric diagnosis associated with insomnia complaint. Very few studies in the general population have been done and still fewer of them have applied a positive and differential diagnosis process. In this study, we used the DSM IV classification to establish positive and differential diagnoses among subjects with insomnia complaints. Compared to other epidemiological studies, our study is distinguished by several aspects: 1) insomnia complaint had a narrower definition. It did not suffice that the subject reported insomnia symptoms, it was also necessary that the subject said s/he was dissatisfied with her/hr/his sleep or that s/he took measures to improve it (medication or sleep hygiene). This choice was motivated essentially by the fact that it is difficult, from a point of clinical point of view, to consider that an individual has insomnia solely based on the presence of symptoms, that, appreciated by a clinician, would resemble insomnia without that they make problem for the subject. 2) Several sleep habits were systematically collected. The majority of epidemiological studies are not centered on sleep problems, with the consequence that results do not allow a global view of factors that are associated with insomnia. 3) The various diagnostic categories of insomnia as well as elements of the differential diagnosis were applied. Thus, we can conclude that insomnia, as a diagnostic entity, including all its forms, is found in 5.6% of the French population. In the majority of cases, the insomnia complaint is part of the symptomatology of a mental disorder, mainly an anxiety disorder. This distinction is important since it helps the physician to determine therapeutic choices. To conclude, it is worthwhile to consider the number of insomnia complainers who had consulted a physician, mainly a general practitioner, in the six months prior to the study. This designates physicians as the first-line resource in the treatment and the prevention of sleep disorders.