Persistent Insomnia: the Role of Objective Short Sleep Duration and Mental Health

61 Persistent Insomnia and Objective Sleep—Vgontzas et al suggested that SDB is associated with chronic insomnia.13,14 However, no longitudinal study to date has examined whether SDB is a risk factor for the persistence of insomnia. Based on previous studies, we have recently suggested that objective sleep duration in chronic insomnia is a marker of the biological severity of the disorder. Previous studies have shown that insomnia with objective short sleep duration is associated with activation of the hypothalamic-pituitary-adrenal (HPA) axis,15-19 hypertension,20 type 2 diabetes,21 neurocognitive deficits,22 and mortality23; whereas insomnia with objective longer sleep duration is associated with normal HPA axis activity,15,16,19 lack of significant medical morbidity,20-22 sleep misperception, anxious-ruminative traits, and poor coping resources.24 However, whether objective short sleep duration plays a role in the persistence of insomnia has not yet been examined. The aim of this study was to examine the role of objective short sleep duration, SDB, and mental and physical health in the persistence of insomnia in a large general random sample (the Penn State Cohort Study) using PSG and a longitudinal design. We hypothesized that objective short sleep duration would be a significant predictor of persistent insomnia.