Daytime Sleepiness from Preschool Children's and Parents' Perspectives: Is There a Difference?

This cross-sectional study investigated the level of daytime sleepiness and sleep-related behaviors in preschool children and compared their self-evaluations with the evaluations of their parents. It was conducted in Split-Dalmatian County, Croatia, among 196 preschool children aged 6-7 years seen at regular medical examinations, accompanied by their parents, using the Epworth sleepiness scale for children and parents/caregivers. Compared to their child's reports, parents tended to underestimate their child's sleepiness while sitting in a classroom at school (p = 0.001) and overestimate their child's sleepiness when lying down to rest or nap in the afternoon (p < 0.001). Boys were sleepier while sitting in a classroom at school during the morning than girls (p = 0.032). As much as 48.2% of preschool children had their own cellphones/tablets. Boys used video games (p < 0.001) and cellphones/tablets more than girls did (p = 0.064). Parental estimation of children playing video games at bedtime was lower than the child's report (p < 0.001). Children who had a TV in their bedroom reported more daytime sleepiness (p = 0.049), and those who played video games at bedtime went to sleep later during the weekend (p = 0.024). Also, children owning cellphone/tablets had longer sleep latency during the weekend compared to children not owning a cellphone (p = 0.015). This study confirmed that parents tend to underestimate children's habits of playing video games at bedtime and children's sleepiness during morning classes. Preschool children who use electronic devices at bedtime more frequently have prolonged sleep latency. These findings provide further evidence of the effects of electronic media devices on preschoolers' sleep patterns and daytime sleepiness.

Depth of SCUBA Diving Affects Cardiac Autonomic Nervous System.

The present study investigated the influence of SCUBA dives with compressed air at depths of 10 and 20 m on ECG-derived HRV parameters in apparently healthy individuals. We hypothesized that cardiac sympathetic activity (measured by HRV parameters) adapts proportionally to diving depth, and that both time- and frequency-domain parameters are sensitive enough to track changes in cardiac ANS function during diving activities and subsequently during the recovery period. Eleven healthy middle-aged recreational divers (nine men and two women, age 43 ± 8, all nonsmokers) volunteered to participate in the present study. The participants (all open-circuit divers) were equipped with dry suits and ECG Holter devices and were later randomly assigned to dive pairs and depths (10 m vs. 20 m), and each participant served as his or her own control. No interaction effects (diving depth x time epoch) were found for the most commonly used HRV markers. More precisely, in response to two different diving protocols, a significant post hoc effect of time was observed for HR and SDNN, as these parameters transiently decreased during the dives and returned to baseline after ascent (p < 0.001). The ULF, VLF (p < 0.003), TP, and LF parameters decreased significantly during the dives, while HF significantly increased (p < 0.003). SCUBA diving apparently challenges the cardiac ANS, even in healthy individuals. The observed changes reveal possible underwater methods of influencing the parasympathetic activity of the heart depending on the depth of the dive. These results identify autonomic nervous system markers to track the cardiovascular risk related to diving and point to the possibility of tracking cardiovascular system benefits during underwater activities in selected patients.

Effects of Oxygen Prebreathing on Bubble Formation, Flow-Mediated Dilatation, and Psychomotor Performance during Trimix Dives.

Introduction: This research was performed to examine the effects of air and oxygen prebreathing on bubble formation, flow-mediated dilatation, and psychomotor performance after scuba dives. Methods: Twelve scuba divers performed two dives using a gas mixture of oxygen, nitrogen, and helium (trimix). In a randomized protocol, they breathed air or oxygen 30 min before the trimix dives. Venous bubble formation, flow-mediated dilatation, and psychomotor performance were evaluated. The participants solved three psychomotor tests: determining the position of a light signal, coordination of complex psychomotor activity, and simple arithmetic operations. The total test solving time, minimum single-task solving time, and median solving time were analyzed. Results: The bubble grade was decreased in the oxygen prebreathing protocol in comparison to the air prebreathing protocol (1.5 vs. 2, p < 0.001). The total test solving times after the dives, in tests of complex psychomotor coordination and simple arithmetic operations, were shorter in the oxygen prebreathing protocol (25 (21-28) vs. 31 (26-35) and 87 (82-108) vs. 106 (90-122) s, p = 0.028). Conclusions: In the oxygen prebreathing protocol, the bubble grade was significantly reduced with no change in flow-mediated dilatation after the dives, indicating a beneficial role for endothelial function. The post-dive psychomotor speed was faster in the oxygen prebreathing protocol.

Sleep and Lifestyle Habits of Medical and Non-Medical Students during the COVID-19 Lockdown.

It has been shown that the measures of social distancing and lockdown might have had negative effects on the physical and mental health of the population. We aim to investigate the sleep and lifestyle habits as well as the mood of Croatian medical (MS) and non-medical students (NMS) during the COVID-19 lockdown. The cross-sectional study included 1163 students (21.6% male), whose lifestyle and sleep habits and mood before and during the lockdown were assessed with an online questionnaire. The shift towards later bedtimes was more pronounced among NMS (~65 min) compared to MS (~38 min), while the shift toward later wake-up times was similar in both MS (~111 min) and NMS (~112 min). All students reported more frequent difficulty in falling asleep, night-time awakenings and insomnia (p < 0.001) during lockdown. A higher proportion of MS reported being less tired and less anxious during lockdown compared to pre-lockdown (p < 0.001). Both student groups experienced unpleasant moods and were less content during lockdown compared to the pre-lockdown period (p < 0.001). Our results emphasize the need for the promotion of healthy habits in the youth population. However, the co-appearance of prolonged and delayed sleep times along with decreased tiredness and anxiety among MS during lockdown reveals their significant workload during pre-lockdown and that even subtle changes in their day schedule might contribute to the well-being of MS.

The Associations between Results in Different Domains of Cognitive and Psychomotor Abilities Measured in Medical Students.

We aimed to investigate the associations between intelligence quotient test scores obtained using the Raven's Advanced Progressive Matrices (APM) and psychomotor testing using the Complex Reactionmeter Drenovac (CRD) test battery, while taking into account previous theoretical approaches recognizing intelligent behavior as the cumulative result of a general biological speed factor reflected in the reaction time for perceptual detections and motor decisions. A total of 224 medical students at the University of Split School of Medicine were recruited. Their IQ scores were assessed using Raven's APM, while the computerized tests of CRD-series were used for testing the reaction time of perception to visual stimulus (CRD311), psychomotor limbs coordination task (CRD411), and solving simple arithmetic operations (CRD11). The total test-solving (TTST) and the minimum single-task-solving (MinT) times were analyzed. On the CRD11 test, task-solving times were shorter in students with higher APM scores (r = -0.48 for TTST and r = -0.44 for MinT; p < 0.001 for both). Negative associations between task-solving times and APM scores were reported on CRD311 (r = -0.30 for TTST and r = -0.33 for MinT, p < 0.001 for both). Negative associations between task-solving times in CRD411 and APM scores (r = -0.40 for TTST and r = -0.30 for MinT, p < 0.001 for both) were found. Faster reaction time in psychomotor limbs coordination tasks, the reaction time of perception to visual stimulus, and the reaction time of solving simple arithmetic operations were associated with a higher APM score in medical students, indicating the importance of mental speed in intelligence test performance. However, executive system functions, such as attention, planning, and goal weighting, might also impact cognitive abilities and should be considered in future research.

Salivary parameters and periodontal inflammation in obstructive sleep apnoea patients.

The aim of this cross-sectional study was to objectively assess the salivary flow rate and composition and periodontal inflammation in obstructive sleep apnoea (OSA) patients. The subjects, who underwent whole-night polysomnography or polygraphy, were referred for saliva sampling and periodontal examination. According to the severity of OSA based on the Apnoea Hypopnea Index (AHI) value, the subjects were classified into groups: no OSA (AHI < 5; N = 17), mild to moderate OSA (AHI 5-29.9; N = 109), and severe OSA (AHI > 30; N = 79). Salivary flow rate, pH, salivary electrolytes, and cortisol were measured from collected saliva samples. Periodontal examination included assessment of the number of teeth, dental plaque, bleeding on probing and periodontal measurements: gingival recession, probing pocket depth, clinical attachment level (CAL) and periodontal inflamed surface area (PISA) score. There were no significant differences in salivary flow rate, salivary pH, salivary electrolyte concentrations or electrolyte ratios among the groups classified according to the severity of OSA. However, subjects without OSA had higher salivary cortisol concentrations than OSA groups (p < 0.001). Increased plaque scores were associated with a higher AHI (r = 0.26; p = 0.003). According to the salivary flow rate, subjects with hyposalivation and reduced salivation had higher concentrations of salivary electrolytes and lower salivary pH than subjects with normal salivation. Subjects with hyposalivation had an increased Mg/PO4 ratio (p < 0.001) and a reduced Ca/Mg ratio (p < 0.001). Furthermore, subjects with severe OSA tended to have higher CALs and plaque volumes. In conclusion, under pathological conditions, such as OSA, multiple interactions might impact salivary flow and electrolyte composition. Complex interrelationships might affect the integrity of oral health, especially considering OSA severity, inflammation, concomitant diseases and medications.

The COVID-19 lockdown promotes changes in sleep habits in the Croatian general population.

AIM: To investigate the effects of the coronavirus disease 2019 (COVID-19) lockdown on sleep habits in the Croatian general population. METHODS: In this cross-sectional study, 1173 respondents from the general population (809 women) completed a self-report online questionnaire that gathered demographic data and data on sleep habits and mood changes before and during the COVID-19 lockdown. RESULTS: During the lockdown, bedtime (from 23:11±1:07 to 23:49±1:32 h, P<0.001) and waketime were delayed (from 6:51±1:09 to 7:49±1:40 h, P<0.001). Sleep latency increased from 10 (5-20) to 15 (10-30) minutes (P<0.001). Bedtime and waketime delays were more pronounced in women and respondents younger than 30. Compared with other age groups, respondents younger than 30 more frequently reported insomnia for the first time during the lockdown and had less frequent night-time awakenings (P<0.001), less common problems falling asleep (P<0.001), less frequently felt calm (P<0.001) and rested (P<0.001), but more frequently felt sadness (P<0.001) and fear (P=0.028). CONCLUSION: The effect of the lockdown on sleep needs to be better understood. Sleep hygiene education could serve a first-line lifestyle intervention for people in lockdown experiencing sleep disruption.

The construction of the Split Sleep Questionnaire on sleep habits during the COVID-19 pandemic in the general population.

AIM: To construct a single-format questionnaire on sleep habits and mood before and during the COVID-19 pandemic in the general population. METHODS: We constructed the Split Sleep Questionnaire (SSQ) after a literature search of sleep, mood, and lifestyle questionnaires, and after a group of sleep medicine experts proposed and assessed questionnaire items as relevant/irrelevant. The study was performed during 2021 in 326 respondents distributed equally in all age categories. Respondents filled out the SSQ, the Pittsburgh Sleep Quality Index (PSQI), and State Trait Anxiety Inventory (STAI), and kept a seven-day sleep diary. RESULTS: Cronbach alpha for Sleep Habits section was 0.819, and 0.89 for Mood section. Test-retest reliability ranged from 0.45 (P=0.036) for work-free day bedtime during the pandemic to 0.779 (P<0.001) for sleep latency before the pandemic. Workday and work-free day bedtime during the COVID-19 pandemic assessed with SSQ were comparable to the sleep diary assessment (P=0.632 and P=0.203, respectively), as was the workday waketime (P=0.139). Work-free day waketime was significantly later than assessed in sleep diary (8:19±1:52 vs 7:45±1:20; P<0.001). No difference in sleep latency was found between the SSQ and PSQI (P = 0.066). CONCLUSION: The SSQ provides a valid, reliable, and efficient screening tool for the assessment of sleep habits and associated factors in the general population during the COVID-19 pandemic.

Periodontitis severity in obstructive sleep apnea patients.

OBJECTIVES: This cross-sectional study investigated the stages of periodontitis in obstructive sleep apnea (OSA) patients and risk factors associated with periodontitis severity among them. MATERIALS AND METHODS: A total of 194 patients underwent a polysomnography/polygraphy and were referred to periodontal examination. According to apnea-hypopnea index (AHI), patients were classified as mild OSA (AHI < 15) and moderate to severe OSA (AHI ≥ 15), whereas periodontitis severity was determined by the clinical attachment level (CAL) according to the recent Classification of Periodontal Diseases and Conditions. Patients were grouped into two categories: stages 1 and 2, and stages 3 and 4. RESULTS: Higher AHI values were reported in OSA patients exhibiting periodontitis stages 3 and 4 compared to OSA patients with periodontitis stages 1 and 2 (p = 0.043) and the non-periodontitis group (p = 0.044). A positive correlation was found between AHI and mean CAL (r = 0.215; p = 0.004), and between AHI and plaque scores (r = 0.292; p < 0.001). Following a multivariable regression analysis, AHI was a significant predictor of mean CAL (ß = 0.169; p = 0.031), explaining 16.4% of variability in mean CAL (adjusted R2 = 0.164; p < 0.001). Older patients had higher odds for an increased mean CAL (ß = 0.266; p = 0.001), as well as patients smoking or formerly smoking (ß = 0.305; p < 0.001) whereas visiting a dental medicine doctor once a year or more often was associated with a decreased mean CAL (ß = - 0.182; p = 0.02). CONCLUSIONS: OSA was associated with severe stages of periodontitis along with increased age, smoking, low frequency of dental visits, and poor oral hygiene. CLINICAL RELEVANCE: Screening for periodontitis is recommended for patients with more severe forms of OSA.

The COVID-19 Lockdown and CPAP Adherence: The More Vulnerable Ones Less Likely to Improve Adherence?

PURPOSE: Due to the possible interplay of factors predisposing to severe COVID-19 outcomes and negative health consequences of poorly controlled OSA, adherence to continuous positive airway pressure (CPAP) therapy among OSA patients might be crucial during COVID-19 pandemics. Lockdown-related changes in CPAP adherence were investigated in CPAP users willing to participate in this study. Pre-lockdown adherence, age, gender, comorbidities and anxiety were analyzed as predictors of COVID-19 lockdown adherence. PATIENTS AND METHODS: A cross-sectional study performed at Split Sleep Medicine Center included 101 severe OSA patients (78.2% male). CPAP memory cards were assessed during 6 months of pre-lockdown and 40 days of lockdown (March/April 2020) period. A total of 81 patients in pre-lockdown met good CPAP adherence criteria (≥4 hours/night on 70% nights). RESULTS: CPAP adherence improved during COVID-19 lockdown in the total sample of severe OSA patients. The percentage of adherent nights and CPAP usage hours per night increased during lockdown in good pre-lockdown CPAP adherers (p=0.011 and p=0.001, respectively), women (p=0.003 and p=0.001, respectively) and respondents younger than 58 years (p=0.007 and p<0.001, respectively). Out of 20/101 poor pre-lockdown CPAP adherers, 9 have shifted to good lockdown adherence. When comorbidities, BMI and anxiety were taken into account, older and male respondents were recognized as less likely to improve CPAP usage hours during lockdown (R2=9.4%; p=0.032). CONCLUSION: The lockdown-related CPAP adherence improved in severe OSA patients, with a shift in almost half of poor pre-lockdown adherers towards good lockdown CPAP adherence. Women, younger and good pre-lockdown CPAP adherers were more adherent during lockdown. Despite being vulnerable groups for both OSA and COVID-19, no expected adherence improvements were observed in men and older patients.

The effect of COVID-19 lockdown on lifestyle and mood in Croatian general population: a cross-sectional study.

AIM: To investigate the effect of the coronavirus 2019 (COVID-19) lockdown on lifestyle behaviors and mood changes in the Croatian general population. METHODS: During ten days of the COVID-19 lockdown in Croatia, 3027 respondents (70.3% female) from the general population completed an online, self-report questionnaire. Demographic data and data on lifestyle habits and mood changes before and during the COVID-19 lockdown were collected. RESULTS: A total of 95.64% of respondents reported to follow most or all restrictions, with female sex (P<0.001) and higher education level (P<0.001) being associated with higher restriction compliance. Women smoked an increased number of cigarettes (P<0.001). The proportion of respondents of both sexes who did not drink or drank 7 drinks per week or more increased (P<0.001). Women also reported lower frequency (P=0.001) and duration of physical exercise (P<0.001). In total, 30.7% of respondents gained weight, with female sex (OR, 2.726) and higher BMI (OR, 1.116; both P<0.001) being associated with an increased likelihood of gaining weight. Both men and women felt more frequently afraid (P<0.001), discouraged (P<0.001), and sad (P<0.001). CONCLUSION: Public health authorities should promote the adoption of healthy lifestyles in order to reduce long-term negative effects of the lockdown.

Obstructive Sleep Apnea Syndrome: A Preliminary Navigated Transcranial Magnetic Stimulation Study.

PURPOSE: An increase in resting motor threshold (RMT), prolonged cortical silent period duration (CSP), and reduced short-latency afferent inhibition (SAI), confirmed with previous transcranial magnetic stimulation (TMS), suggest decreased cortical excitability in obstructive sleep apnea syndrome (OSAS). The present study included MRI of OSAS patients for navigated TMS assessment of the RMT, as an index of the threshold for corticospinal activation at rest, and SAI as an index of cholinergic neurotransmission. We hypothesize to confirm findings on SAI and RMT with adding precision in the targeting of motor cortex in OSAS. SUBJECTS AND METHODS: After acquiring head MRIs for 17 severe right-handed OSAS and 12 healthy subjects, the motor cortex was mapped with nTMS to assess the RMT and SAI, with motor evoked potentials (MEPs) recorded from the abductor-pollicis brevis (APB) muscle. The 120%RMT intensity was used for the SAI by a paired-pulse paradigm in which the electrical stimulation to the median nerve is followed by magnetic stimulation of the motor cortex at inter-stimulus intervals (ISIs) of 18-28 ms (ISIs18-28). The SAI control condition included a recording of MEPs without peripheral stimulation. Latency and amplitude of MEP at RMT at 120%RMT for eleven different at ISIs18-28 were analyzed. RESULTS: The study showed a significantly lower percentage deviation of MEP amplitude at ISIs(18-28ms) from the control condition between OSAS and healthy subjects (U=44.0, p=0.01). The intensity of stimulation at RMT was significantly higher in OSAS subjects (U=55.0, p=0.04*). Correlation analysis showed that BMI significantly negatively correlated (ρ=-0.47) with MEP amplitude percentage deviation in OSAS patients. CONCLUSION: The nTMS study results in increased RMT, and reduced cortical afferent inhibition in OSAS patients for SAI at ISIs18-28, confirming previous findings of impaired cortical afferent inhibition in OSAS. Future nTMS studies are desirable to elucidate the role of RMT and SAI in diagnostics and treatment of OSAS, and to elucidate the usefulness of nTMS in OSAS research.

The effect of age and gender on cognitive and psychomotor abilities measured by computerized series tests: a cross-sectional study.

AIM: To assess age- and gender-associated differences in cognitive and psychomotor abilities measured by the Complex Reactionmeter Drenovac (CRD-series) tests. METHODS: This cross-sectional study, conducted between 2009 and 2019, enrolled 3420 participants (2012 women) in the age ranging from 18 to 88 years. The participants solved three CRD-series chronometric tests: discrimination of the light signal position (CRD311), complex psychomotor coordination (CRD411), and simple arithmetic operations (CRD11). We analyzed total test solving time (TTST), minimum single task solving time (MinT), number of errors, initial dissociation, and start, end, and total ballasts as measures of wasted time in the first half of the test, second half of the test, and total test time, respectively. RESULTS: Age was positively associated with MinT and TTST in all used tests (P<0.001), while initial dissociation, start ballast, and end ballast significantly increased with age (P<0.001). On the CRD11 test, men had shorter TTST than women (P=0.012), shorter start, end, and total ballasts (P<0.001), and made fewer errors than women (P<0.001). On the CRD311 test, women had shorter start (P=0.002), end, and total ballast (P<0.001) than men. On the CRD411 test, men performed better than women on all variables (P<0.001). CONCLUSION: Decreased cognitive and psychomotor abilities measured by the CRD-series tests were associated with advanced age. Men performed better than women on simple arithmetic and complex psychomotor coordination tests, whereas women lost less time on the test of light signal position discrimination.

Psychomotor Performance in Patients with Obstructive Sleep Apnea Syndrome.

PURPOSE: Determinants of obstructive sleep apnea (OSA) are hypoxemia and hypercapnia, as well as (micro) arousals from sleep, resulting in chronic sleep fragmentation, sleep deprivation, and excessive daytime sleepiness (EDS). All of the above-mentioned factors might contribute to psychomotor impairment seen in OSA patients. Additionally, this study aimed to assess the contribution of BMI, age, EDS assessed with Epworth sleepiness scale (ESS), and severity of OSA assessed with apnea-hypopnea index (AHI) to the reaction time on chronometric tests in OSA patients and controls. It is hypothesized that moderate and severe OSA have adverse effects on reaction time of perception to visual stimulus, of solving simple arithmetic operations, and of psychomotor limbs coordination assessed by chronometric psychodiagnostic test battery. PATIENTS AND METHODS: This study was conducted on 206 male participants; 103 of them had moderate or severe OSA diagnosed by whole-night polysomnography/polygraphy. Control participants (N=103), matched to patients with OSA by age and BMI, had no reported OSA in their medical history, no increased risk for OSA, nor EDS. All participants were assessed with three chronometric psychodiagnostic tests, measuring the reaction time of perception to visual stimulus, of solving simple arithmetic operations, and of psychomotor limbs coordination. RESULTS: Participants from the OSA group achieved impaired results compared to control participants in minimum single task solving time in speed of solving simple arithmetic operations (3±0.9 and 2.6±0.6, P<0.001), and in minimum solving time of a single task in complex psychomotor limbs coordination (0.69±0.2 and 0.61±0.1, P=0.007). Regression analysis revealed no significant contribution of daytime sleepiness to the results achieved in each of the tests. CONCLUSION: It is concluded that severe OSA impaired speed of perception, convergent, and operative thinking. Moreover, it is suggested that EDS did not contribute to poor psychomotor outcome in patients with OSA in this study, when age was controlled for.

Influence of oxygen enriched gases during decompression on bubble formation and endothelial function in self-contained underwater breathing apparatus diving: a randomized controlled study.

AIM: To assess the effect of air, gas mixture composed of 50% nitrogen and 50% oxygen (nitrox 50), or gas mixture composed of 1% nitrogen and 99% oxygen (nitrox 99) on bubble formation and vascular/endothelial function during decompression after self-contained underwater breathing apparatus diving. METHODS: This randomized controlled study, conducted in 2014, involved ten divers. Each diver performed three dives in a randomized protocol using three gases: air, nitrox 50, or nitrox 99 during ascent. The dives were performed on three different days limited to 45 m sea water (msw) depth with 20 min bottom time. Nitrogen bubbles formation was assessed by ultrasound detection after dive. Arterial/endothelial function was evaluated by brachial artery flow mediated dilatation (FMD) before and after dive. RESULTS: Nitrox 99 significantly reduced bubble formation after cough compared with air and nitrox 50 (grade 1 vs 3 and vs 3, respectively, P=0.026). Nitrox 50 significantly decreased post-dive FMD compared with pre-dive FMD (3.62 ± 5.57% vs 12.11 ± 6.82% P=0.010), while nitrox 99 did not cause any significant change. CONCLUSION: Nitrox 99 reduced bubble formation, did not change post-dive FMD, and decreased total dive duration, indicating that it might better preserve endothelial function compared with air and nitrox 50 dive protocols.

Effects of CPAP therapy on cognitive and psychomotor performances in patients with severe obstructive sleep apnea: a prospective 1-year study.

STUDY OBJECTIVES: We prospectively investigated the effects of continuous positive airway pressure (CPAP) on long-term cognitive and psychomotor performances, and excessive daytime sleepiness in severe obstructive sleep apnea (OSA) patients. METHODS: A total of 40 patients were recruited and 23 patients with severe OSA fully completed the study protocol to investigate the effects of CPAP therapy on psychomotor performance at 1, 3, and 6 months and 1 year following initiation of the therapy. Psychomotor CRD-series tests measuring reaction times of light stimulus perception, solving simple arithmetic operations, and complex psychomotor limb coordination, were used in this study. The data collected following CPAP therapy were compared to baseline values prior to the CPAP treatment for each patient. RESULTS: All of the measured variables improved following CPAP treatment. However, the most pronounced effect was observed in improvement of reaction times to complex psychomotor limb coordination test (p < 0.05). Self-reported evaluation of excessive daytime sleepiness measured by Epworth Sleepiness Scale (ESS) showed significant decrease from 10.0 ± 1.1 before to 3.5 ± 0.5 (p < 0.001), after 1 year on CPAP therapy. CONCLUSIONS: The CPAP therapy improved cognitive and psychomotor performance on CRD-series tests with the most significant improvement observed in complex psychomotor limb coordination of severe OSA patients.

Phrenic long-term depression evoked by intermittent hypercapnia is modulated by serotonergic and adrenergic receptors in raphe nuclei.

Intermittent hypercapnia evokes prolonged depression of phrenic nerve activity (phrenic long-term depression, pLTD). This study was undertaken to investigate the role of 5-HT and α2-adrenergic receptors in the initiation of pLTD. Adult male urethane-anesthetized, vagotomized, paralyzed, and mechanically ventilated Sprague-Dawley rats were exposed to a protocol of acute intermittent hypercapnia (AIHc; 5 episodes of 15% CO2 in air, each episode lasting 3 min). The experimental group received microinjection of the selective 5-HT1A receptor agonist 8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT), the broad-spectrum 5-HT antagonist methysergide, or the α2-adrenergic antagonist yohimbine, whereas the control group received microinjection of 0.9% saline into the caudal raphe region. Peak phrenic nerve activity (pPNA) and burst frequency ( f) were analyzed during baseline (T0), during 5 hypercapnic episodes (THc1-THc5), and at 15, 30, and 60 min after the end of the last hypercapnic episode. In the control group, pPNA decreased 60 min after the end of the last hypercapnic episode compared with baseline values, i.e., pLTD developed ( P = 0.023). In the 8-OH-DPAT group, pPNA significantly decreased at T15, T30, and T60 compared with baseline values, i.e., pLTD developed ( P = 0.01). In the methysergide and yohimbine groups, AIHc did not evoke significant changes of the pPNA at T15, T30, and T60 compared with baseline values. In conclusion, activation of 5-HT1A receptors accentuated induction of pLTD, whereas blockade of α2-adrenergic receptors prevented development of pLTD following AIHc in anesthetized rats. These results suggest that chemical modulation of 5-HT and α2-adrenergic receptors in raphe nuclei affects hypercapnia-induced pLTD, offering important insights in understanding the mechanisms involved in development of respiratory plasticity. NEW & NOTEWORTHY Hypercapnia is a concomitant feature of many breathing disorders, including obstructive sleep apnea. In this study, acute intermittent hypercapnia evoked development of phrenic long-term depression (pLTD) 60 min after the last hypercapnic episode that was preserved if the selective 5-HT1A receptor agonist 8-hydroxy-2-(dipropylamino)tetralin hydrobromide was microinjected in the caudal raphe region before the hypercapnic stimulus. This study highlights that both 5-HT and adrenergic receptor activation is needed for induction of pLTD in urethane-anesthetized rats following intermittent hypercapnia exposure.

Good and poor sleepers among OSA patients: sleep quality and overnight polysomnography findings.

Previous studies aimed to determine if Pittsburgh sleep quality index (PSQI) is a valid screening instrument for obstructive sleep apnea, indicating its disadvantages. However, the rationale of PSQI use in sleep clinics is not the screening, but the assessment of sleep quality itself. Therefore, the aims of this study were to investigate the sleep quality in obstructive sleep apnea patients and to identify the cutoff point for differentiation of "good" and "poor" sleepers among them. We constructed the Croatian version of PSQI and assessed its psychometric properties. The protocol of the study included the assessment of sleep quality in 130 obstructive sleep apnea patients and 75 healthy control subjects. All subjects completed the Croatian version of the PSQI, and the patients underwent overnight polysomnography screening. Obstructive sleep apnea patients had higher values of the global PSQI component score, indicating lower sleep quality, compared to a healthy control group (p < 0.001). The psychometric properties of PSQI scores in the prediction of normal sleep efficiency indicate that the cutoff score of 9.5 differentiates patients in total sleep time (p <  0.001), REM duration (p = 0.014), sleep efficiency (p = 0.001), time spent awake during sleep (p = 0.006), after sleep (p = 0.024), and after sleep onset (p = 0.001). In OSA patients, a PSQI cutoff score of 9.5 differentiated good and poor sleepers significantly in total sleep time, REM duration, time spent awake during sleep, and WASO time. Current findings enhance the interpretability of PSQI results in a population of OSA patients.

Improvement of Cognitive and Psychomotor Performance in Patients with Mild to Moderate Obstructive Sleep Apnea Treated with Mandibular Advancement Device: A Prospective 1-Year Study.

STUDY OBJECTIVES: This study aimed to provide the evidence on effect of mandibular advancement device (MAD) therapy on long-term cognitive and psychomotor performance, excessive daytime sleepiness, and quality of life in patients with mild to moderate obstructive sleep apnea (OSA). METHODS: A total of 15 patients with mild to moderate OSA were treated with MAD therapy and they were followed up after 3 mo and 1 y of therapy. The patients were tested on three different tests of cognitive and psychomotor performance using the computer-based system Complex Reactionmeter Drenovac (CRD-series) at baseline and at the time of follow-up, and the 36-Item Short Form Health Survey (SF-36) questionnaire and Epworth Sleepiness Scale were used to assess their quality of life and excessive daytime sleepiness, respectively. RESULTS: The mean apnea-hypopnea index (AHI) decreased significantly from 22.9 ± 5.9 events/h at baseline, to 9.7 ± 4.5 events/h after 1 y of MAD therapy (p < 0.001). There was significant improvement on all three CRD-series tests used after 1 y of MAD therapy, considering total test solving time (TTST) and minimal single task solving time (MinT), whereas total number of errors committed during the tests (TE) remained unchanged. Self-reported measures, excessive daytime sleepiness, and three domains of quality of life, social functioning, general health perception, and health change following MAD therapy showed significant improvements after 1 y of MAD therapy. CONCLUSIONS: This study demonstrates significant improvements in cognitive and psychomotor performance, particularly in the domain of perceptive abilities, convergent thinking (constructing and solving simple mathematical tasks) and psychomotor reaction times, excessive daytime sleepiness, and quality of life in patients with mild to moderate OSA following MAD therapy.

Intermittent hypercapnia-induced phrenic long-term depression is revealed after serotonin receptor blockade with methysergide in anaesthetized rats.

NEW FINDINGS: What is the central question of this study? Intermittent hypercapnia is a concomitant feature of breathing disorders. Hypercapnic stimuli evoke a form of respiratory plasticity known as phrenic long-term depression in experimental animals. This study was performed to investigate the putative role of serotonin receptors in the initiation of phrenic long-term depression in anaesthetized rats. What is the main finding and its importance? Phrenic nerve long-term depression was revealed in animals pretreated with the serotonin broad-spectrum antagonist, methysergide. This study highlights that serotonin receptors modulate respiratory plasticity evoked by acute intermittent hypercapnia in anaesthetized rats. This study was performed to test the hypothesis that intermittent hypercapnia can evoke a form of respiratory plasticity known as long-term depression of the phrenic nerve (pLTD) and that 5-HT receptors play a role in the initiation of pLTD. Adult male urethane-anaesthetized, vagotomized, paralysed, mechanically ventilated Sprague-Dawley rats were exposed to an acute intermittent hypercapnia protocol. One group received i.v. injection of the non-selective 5-HT receptor antagonist methysergide and another group received i.v. injection of the selective 5-HT1A receptor antagonist WAY-100635 20 min before exposure to intermittent hypercapnia. A control group received i.v. injection of saline. Peak phrenic nerve activity and respiratory rhythm parameters were analysed at baseline (T0), during each of five hypercapnic episodes, and 15, 30 and 60 min (T60) after the last hypercapnia. Intravenous injection of methysergide before exposure to acute intermittent hypercapnia induced development of amplitude pLTD at T60 (decreased by 46.1 ± 6.9%, P = 0.003). Conversely, in control and WAY-100635-pretreated animals, exposure to acute intermittent hypercapnia did not evoke amplitude pLTD. However, a long-term decrease in phrenic nerve frequency was evoked both in control (42 ± 4 breaths min(-1) at T0 versus 32 ± 5 breaths min(-1) at T60; P = 0.036) and in methysergide-pretreated animals (42 ± 2 breaths min(-1) at T0 versus 32 ± 3 breaths min(-1) at T60; P = 0.028). In WAY-100635 pretreated animals, frequency pLTD was prevented. These results suggest that 5-HT receptors modulate respiratory plasticity induced by acute intermittent hypercapnia in anaesthetized rats.