Insomnia Symptoms in a Swiss Population-Based Cohort: Prevalence, Clinical Correlates and Polysomnographic Alterations.

This study assessed the prevalence, clinical correlates and polysomnographic features of insomnia symptoms in a population-based cohort (HypnoLaus, Lausanne, Switzerland). Data were obtained from 3947 participants (mean age 57.5 ± 10.5 years; range 40-82; 52.0% female). Insomnia symptoms were defined as difficulty initiating or maintaining sleep ≥ 3 nights/week during the past month or regular hypnotic use. Independent correlates of insomnia symptoms were examined using logistic regression. In the subset of 1718 participants who underwent polysomnography (performed 1.1 ± 0.9 years after insomnia symptom assessment), associations between insomnia symptoms and sleep variables were examined using linear regression models adjusted for age, sex, depression, anxiety and psychotropic use. Insomnia symptoms affected 32.0% of participants, and 4.2% of the total sample reported regular hypnotic use. Independent correlates included older age, female sex, lower education, dyslipidaemia, lower likelihood of current smoking, excessive alcohol consumption, depression, anxiety, psychotropic use and daytime sleepiness. Compared with those without symptoms, participants with insomnia showed shorter total sleep time, longer sleep onset latency, longer wake after sleep onset and lower sleep efficiency (all small effect sizes). Sleep microstructure analysis showed higher odds ratio product (ORP) values (in wake, NREM, and N2, and ORP-9), higher normalised EEG power, higher beta power and higher gamma power (all small effect sizes). Insomnia symptoms are highly prevalent in this population-based cohort and are linked to multiple sociodemographic and clinical factors. Polysomnographic findings indicate modest sleep macrostructural differences, whereas microstructural alterations, although subtle in magnitude, appeared more consistently associated with insomnia symptoms.