Sleep disturbance frequently occurs in patients with mild cognitive impairment (MCI) and appears to be involved in the cellular and molecular mechanisms of cognitive decline. The aim of this systematic review is to clarify whether patients with MCI demonstrate alterations in certain sleep parameters: total sleep time (TST), sleep efficiency (SE), sleep latency (SL), rapid eye movement latency (REML), percent of rapid eye movement (REM%), arousal index (AI), wake after sleep onset (WASO), slow-wave sleep (SWS), periodic leg movement in sleep (PLMS), and cyclic alternating pattern (CAP) through polysomnography (PSG) and actigraphy. Databases including PubMed, Web of Science, Embase, ScienceDirect, Cochrane, CBM, CNKI, Wanfang Data, and VIP were searched up to January 2016 to collect literature on the correlation between sleep disturbance and MCI as assessed by objective measures. Meta-analysis was conducted using the Review Manager 5.3 software. A total of ten case-control studies involving 225 MCI patients and 235 healthy elders (HE) were deemed eligible and included in our meta-analysis. Every type of sleep disturbance was present in our studies with significant differences in the MCI subtypes. Compared with HE, overall MCI patients as a group expressed more SL and less SE; MCI patients showed less TST and SE and more SL and CAP; patients with amnestic mild cognitive impairment (aMCI) had less AI; patients with non-amnestic mild cognitive impairment (naMCI) had more TST and less AI. Patients with naMCI expressed more AI than those with aMCI. The results indicate that MCI patients might experience more serious sleep disturbance and that different MCI subtypes have different patterns of sleep disturbance.
Most models evaluated by the Intergovernmental Panel for Climate change estimate projected increases in temperature and precipitation with rising atmospheric CO2 levels. Researchers have suggested that increases in CO2 and associated increases in temperature and precipitation may stimulate vegetation growth and increase evapotranspiration (ET), which acts as a cooling mechanism, and on a global scale, may
OPEN ACCESSHydrology 2015, 2 94 slow the climate-warming trend. This hypothesis has been modeled under increased CO2 conditions with models of different vegetation-climate dynamics. The significance of this vegetation negative feedback, however, has varied between models. Here we conduct a century-scale observational analysis of the Eastern US water balance to determine historical evapotranspiration trends and whether vegetation greening has affected these trends. We show that precipitation has increased significantly over the twentieth century while runoff has not. We also show that ET has increased and vegetation growth is partially responsible.
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