Insomnia with objective short sleep duration is associated with deficits in neuropsychological performance: a general population study.

TLDR: It is suggested that objective sleep duration may predict the severity of chronic insomnia, including its effect on neurocognitive function.

Abstract: INSOMNIA IS THE MOST COMMON SLEEP DISORDER, YET LITTLE IS KNOWN ABOUT THE MECHANISMS, CAUSES, CLINICAL COURSE, AND CONSEQUENCES of this highly prevalent chronic condition.1 Many studies have established that insomnia is highly comorbid with psychiatric disorders and is a risk factor for the development of depression, anxiety, and suicide.2 However, the evidence on the association of insomnia with medical morbidity is very limited.1,2 Although insomniacs commonly complain of cognitive deficits, mainly of attention and concentration, there is a surprising lack of evidence to suggest a link between chronic insomnia and cognitive dysfunction in objective testing.3–5 In fact, published reviews demonstrated poorer performance among patients with insomnia in only a small number of studies (approximately 10% to 25%), according to the 2006 Standards in Insomnia Committee. Thus they concluded that no specific psychomotor or cognitive-performance measure can be recommended for routine use in insomnia studies.6 In the 3 most recent studies,7–9 using polysomnography and performance data to compare insomniacs to normal sleepers, results were mixed. Two of 3 studies included only small sample sizes, whereas the third included a relatively large group of research volunteer primary insomniacs and used a rather narrowly focused battery. To date, our sample is the largest population-based study using full polysomnography and a comprehensive neuropsychological battery that has been conducted in adults to investigate the association of insomnia and performance. We have previously reported that objective short sleep duration in insomnia may be an index of the biological severity of the disorder. Specifically, insomnia with short sleep duration has been shown to be associated with a high risk for hypertension10 and type 2 diabetes11 as well as with activation of the hypothalamic-pituitary-adrenal (HPA) axis.12–14 The latter finding is particularly relevant to neuropsychological performance because hyperactivity of the HPA axis has been shown to be associated with neurocognitive deficits.15–18 Based on these observations, we speculate that insomniacs with short sleep duration may be at high risk for deficits in neuropsychological performance. In order to test this hypothesis, we examined the joint effects of the complaint of chronic insomnia and objective sleep duration on the neuropsychological performance of a large cross-sectional population-based sample from The Penn State Cohort.