Sleep-wake patterns and sleep quality in urban Georgia

Sleep problems represent a worldwide health concern but their prevalence and impacts are unknown in most non-European/North American countries. This study aimed to evaluate sleep-wake patterns, sleep quality and potential correlates of poor sleep in a sample of the urban Georgian population

Sleep-wake patterns and sleep quality in urban Georgia

OBJECTIVES: Sleep problems represent a worldwide health concern but their prevalence and impacts are unknown in most non-European/North American countries. This study aimed to evaluate sleep-wake patterns, sleep quality and potential correlates of poor sleep in a sample of the urban Georgian population. METHODS: Analyses are based on 395 volunteers (267 females, 128 males, aged 20-60 years) of the Georgia Somnus Study. Subjects completed the Pittsburgh Sleep Quality Index (PSQI) and the Beck Depression Inventory-Short Form. Sociodemographic information and self-reported height and weight were collected. RESULTS: 43% of subjects had poor sleep quality (PSQI > 5). Further, 41% had low sleep efficiency, 27.6% slept 6 hours or less, 32.4% went to bed after midnight, 27.6% snored, 10.6% were taking sleep medication, and 26.8% had sleep maintenance problems as occurring three or more times a week. The latest bedtime, rise time, and gender effect on these variables were found in the age group 20-29 years. PSQI global score showed a significant age but not gender difference. The economic status and the depression score were two significant predictors of sleep quality. CONCLUSIONS: Poor sleep quality has a high prevalence and is strongly linked to the economic status. Study findings call for a global assessment of sleep problems in countries where sleep disturbances represent an insufficiently recognized public health issue

Modulation of Hyperpolarization-Activated Inward Current and Thalamic Activity Modes by Different Cyclic Nucleotides

The hyperpolarization-activated inward current, Ih, plays a key role in the generation of rhythmic activities in thalamocortical (TC) relay neurons. Cyclic nucleotides, like 3′,5′-cyclic adenosine monophosphate (cAMP), facilitate voltage-dependent activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels by shifting the activation curve of Ih to more positive values and thereby terminating the rhythmic burst activity. The role of 3′,5′-cyclic guanosine monophosphate (cGMP) in modulation of Ih is not well understood. To determine the possible role of the nitric oxide (NO)-sensitive cGMP-forming guanylyl cyclase 2 (NO-GC2) in controlling the thalamic Ih, the voltage-dependency and cGMP/cAMP-sensitivity of Ih was analyzed in TC neurons of the dorsal part of the lateral geniculate nucleus (dLGN) in wild type (WT) and NO-GC2-deficit (NO-GC2−/−) mice. Whole cell voltage clamp recordings in brain slices revealed a more hyperpolarized half maximal activation (V1/2) of Ih in NO-GC2−/− TC neurons compared to WT. Different concentrations of 8-Br-cAMP/8-Br-cGMP induced dose-dependent positive shifts of V1/2 in both strains. Treatment of WT slices with lyase enzyme (adenylyl and guanylyl cyclases) inhibitors (SQ22536 and ODQ) resulted in further hyperpolarized V1/2. Under current clamp conditions NO-GC2−/− neurons exhibited a reduction in the Ih-dependent voltage sag and reduced action potential firing with hyperpolarizing and depolarizing current steps, respectively. Intrathalamic rhythmic bursting activity in brain slices and in a simplified mathematical model of the thalamic network was reduced in the absence of NO-GC2. In freely behaving NO-GC2−/− mice, delta and theta band activity was enhanced during active wakefulness (AW) as well as rapid eye movement (REM) sleep in cortical local field potential (LFP) in comparison to WT. These findings indicate that cGMP facilitates Ih activation and contributes to a tonic activity in TC neurons. On the network level basal cGMP production supports fast rhythmic activity in the cortex