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Sijana Demirovic,1,2 Linda Lusic Kalcina,1,2 Ivana Pavlinac Dodig,1,2 Renata Pecotic,1,2 Maja Valic,1,2 Natalija Ivkovic,2 Zoran Dogas1,2 1Department of Neuroscience, University of Split School of Medicine, Split, Croatia; 2Split Sleep Medicine Center, University Hospital Center Split, Split, CroatiaCorrespondence: Zoran DogasDepartment of Neuroscience, University of Split School of Medicine, Soltanska 2, Split, 21000, CroatiaTel + 385 21 557 858Fax + 385 21 557 955Email zoran.dogas@mefst.hrPurpose: 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.Keywords: OSA, CPAP, CPAP adherence, COVID-19, lockdown

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 (β = 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 (β = 0.266 ; p = 0.001), as well as patients smoking or formerly smoking (β = 0.305 ; p < 0.001) whereas visiting a dental medicine doctor once a year or more often was associated with a decreased mean CAL (β = - 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.

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

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

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. During the lockdown, bedtime (from 23:11±1:07 to 23:49±1:32 h, P

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.

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 psychomo- tor coordination (CRD411), and simple arithmetic opera- tions (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 mea- sures 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 abili- ties measured by the CRD-series tests were associated with advanced age. Men performed better than women on simple arithmetic and complex psychomotor coordina- tion tests, whereas women lost less time on the test of light signal position discrimination.

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.

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.

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.

Phrenic long-term facilitation (pLTF) is a form of respiratory plasticity, manifested by prolonged increase in peak amplitude of phrenic nerve activity (PNA) after episodes of acute intermittent hypoxia (AIH). The aim was to investigate the effects of sevoflurane and isoflurane monoanesthesia at equipotent anesthetic doses on the expression of amplitude pLTF. Experiments were performed on Sprague-Dawley anesthetized, vagotomized, and mechanically ventilated rats. Two experimental groups, sevoflurane and isoflurane, and a control group (urethane-anesthetized) were formed. Peak amplitude of phrenic nerve activity, respiratory frequency and breathing rhythm parameters (Ti, inspiratory duration ; Te, expiratory duration ; and Ttot, total respiratory time duration) were analyzed during hypoxic episodes, and at 15, 30, and 60min after the last hypoxic episode. In the control group average PNA increased by 173.03±70.16% (p0.05). Amplitude pLTF was abolished during sevoflurane and isoflurane monoanesthesia.

Summary Obstructive sleep apnoea (OSA) is characterized by periods of upper airway collapse accompanied by repeated episodes of hypoxia. In experimental animals repeated bouts of hypoxia may evoke sustained augmentation of phrenic nerve activity, known as phrenic long-term facilitation (pLTF). This form of physiological compensation might contribute to stable breathing, minimizing the occurrence of apnoeas and/or hypopnoeas during sleep in patients with OSA. Serotonin (5-HT) has been shown to modulate respiratory neuronal activity, possibly via projections originating in the raphe nuclei. Our model focuses on the effects of 5-HT1A receptors blockade by selective antagonist WAY-100635 into the caudal raphe region on phrenic long-term facilitation after exposure to acute intermittent hypoxia (AIH) episodes. Adult, male, urethane-anaesthetized, vagotomized, paralyzed and mechanically ventilated Sprague–Dawley rats were exposed to AIH protocol. Experimental group received microinjection of WAY-100635 into the caudal raphe nucleus, whereas the control group received saline into the same site. Peak phrenic nerve activity and respiratory rhythm parameters were analysed during five hypoxic episodes, as well as at 15, 30 and 60 min after the end of hypoxias. In the control group, 1 h post-hypoxia pLTF was developed. Microinjections of selective 5-HT1A receptor antagonist WAY-100635 into the raphe nuclei prior to the AIH protocol prevented induction of pLTF. These results suggest that 5-HT1A receptor activation at supraspinal level is important for induction of pLTF, which is suggested to be an important respiratory neuroplasticity model in animal studies that possibly correlates with OSA in humans.

This study was performed to investigate long-term changes of peak phrenic (pPNA) and renal sympathetic nerve (RSNA) activities during and following acute intermittent hypercapnic exposures. Urethan...

Growing awareness of obstructive sleep apnea syndrome (OSAS) has increased the need for concise and reliable screening tools. The Epworth sleepiness scale (ESS) has been validated in numerous languages and ethnic groups, since it was originally designed for the English-speaking population. The STOP questionnaire was developed as a novel OSAS screening tool in surgical patients, but has not been validated in the general population. The present study was undertaken to provide reliable and validated ESS in the Croatian language and to evaluate the ESS and STOP as screening instruments for OSAS. METHODS: The Croatian version of ESS and STOP questionnaire was administered to 217 patients referred to the Split Sleep Medicine Center and 208 healthy control subjects. Test-retest reliability was investigated in 20 healthy subjects. RESULTS: The ESS score was significantly higher for the patients referred to the Split Sleep Medicine Center compared to the control group (8.2 ± 5.0 vs. 5.9 ± 3.8, p < 0.001). Cronbach's alpha coefficient for the ESS Croatian version was 0.84 indicating an excellent internal consistency. Reproducibility revealed no significant difference in each item or in the total ESS scores. Receiver operating curve of the ESS for identification of cases with AHI >5/h was 0.64, and for the STOP questionnaire, it was 0.84. CONCLUSIONS: Both ESS and STOP questionnaires successfully distinguished healthy subjects from subjects with OSAS. The STOP questionnaire had better probability to correctly predict high-risk patients for OSAS compared to ESS. We propose that the STOP questionnaire could be used as an easy- to-use and accurate screening tool in identification of patients with risk for OSAS in the general population, but it has not been tested in the Croatian population yet.

Obstructive sleep apnoea (OSA) is characterized by periods of upper airway collapse accompanied by repeated episodes of hypoxia. In experimental animals repeated bouts of hypoxia may evoke sustained augmentation of phrenic nerve activity, known as phrenic long-term facilitation (pLTF). This form of physiological compensation might contribute to stable breathing, minimizing the occurrence of apnoeas and/or hypopnoeas during sleep in patients with OSA. Serotonin (5-HT) has been shown to modulate respiratory neuronal activity, possibly via projections originating in the raphe nuclei. Our model focuses on the effects of 5-HT1A receptors blockade by selective antagonist WAY-100635 into the caudal raphe region on phrenic long-term facilitation after exposure to acute intermittent hypoxia (AIH) episodes. Adult, male, urethane-anaesthetized, vagotomized, paralyzed and mechanically ventilated Sprague-Dawley rats were exposed to AIH protocol. Experimental group received microinjection of WAY-100635 into the caudal raphe nucleus, whereas the control group received saline into the same site. Peak phrenic nerve activity and respiratory rhythm parameters were analysed during five hypoxic episodes, as well as at 15, 30 and 60 min after the end of hypoxias. In the control group, 1 h post-hypoxia pLTF was developed. Microinjections of selective 5-HT1A receptor antagonist WAY-100635 into the raphe nuclei prior to the AIH protocol prevented induction of pLTF. These results suggest that 5-HT1A receptor activation at supraspinal level is important for induction of pLTF, which is suggested to be an important respiratory neuroplasticity model in animal studies that possibly correlates with OSA in humans.