Sleep Extension Improves Neurocognitive Functions in Chronically Sleep-Deprived Obese Individuals

Background Sleep deprivation and obesity, are associated with neurocognitive impairments. Effects of sleep deprivation and obesity on cognition are unknown, and the cognitive long-term effects of improvement of sleep have not been prospectively assessed in short sleeping, obese individuals. Objective To characterize neurocognitive functions and assess its reversibility. Design Prospective cohort study. Setting Tertiary Referral Research Clinical Center. Patients A cohort of 121 short-sleeping (<6.5 h/night) obese (BMI 30–55 kg/m 2 ) men and pre-menopausal women. Intervention Sleep extension (468±88 days) with life-style modifications. Measurements Neurocognitive functions, sleep quality and sleep duration. Results At baseline, 44% of the individuals had an impaired global deficit score ( t -score 0–39). Impaired global deficit score was associated with worse subjective sleep quality (p = 0.02), and lower urinary dopamine levels (p = 0.001). Memory was impaired in 33%; attention in 35%; motor skills in 42%; and executive function in 51% of individuals. At the final evaluation (N = 74), subjective sleep quality improved by 24% (p<0.001), self-reported sleep duration increased by 11% by questionnaires (p<0.001) and by 4% by diaries (p = 0.04), and daytime sleepiness tended to improve (p = 0.10). Global cognitive function and attention improved by 7% and 10%, respectively (both p = 0.001), and memory and executive functions tended to improve (p = 0.07 and p = 0.06). Serum cortisol increased by 17% (p = 0.02). In a multivariate mixed model, subjective sleep quality and sleep efficiency, urinary free cortisol and dopamine and plasma total ghrelin accounted for 1/5 of the variability in global cognitive function. Limitations Drop-out rate. Conclusions Chronically sleep-deprived obese individuals exhibit substantial neurocognitive deficits that are partially reversible upon improvement of sleep in a non-pharmacological way. These findings have clinical implications for large segments of the US population. Trail registration www.ClinicalTrials.gov NCT00261898. NIDDK protocol 06-DK-0036