Sami Myllymaa

University of Eastern Finland | UEF · Department of Applied Physics

Background Major cardiovascular events (MACE) and mortality in obstructive sleep apnea (OSA) patients have been frequently reported. However, there is an ongoing debate regarding biomarkers predicting MACE and mortality in OSA. The Apnoea Hypopnea Index (AHI) has been used to assess the severity of Obstructive Sleep Apnea (OSA) despite poor associa...

Objective: Hypoxic load is one of the main characteristics of obstructive sleep apnea (OSA) contributing to sympathetic overdrive and weakened cardiorespiratory coupling (CRC). Whether this association changes with increasing hypoxic load has remained obscure. Therefore, we aimed to study our hypothesis that increasing hypoxic load acutely decreas...

Six potential thin film candidates, Bi, Ti, Al2O3, Ag, Au, and C, were prepared on Si substrate to determine the most suitable ones to detect three known salivary biomarkers, L-Fucose, L-Proline, and N-acetylneuraminic acid from surface-enhanced Raman spectrum. In the two-phase study, 5 mg of each biomarker substance was first diluted into 1 ml of...

Sleep recordings are increasingly being conducted in patients' homes where patients apply the sensors themselves according to instructions. However, certain sensor types such as cup electrodes used in conventional polysomnography are unfeasible for self-application. To overcome this, self-applied forehead montages with electroencephalography and el...

Three-dimensional (3D) printing has a high potential in various biomedical applications. We hypothesise that 3D printing could be a viable option to construct bioimpedance spectroscopic (BIS) sensors suitable for electrochemical characterization of oral mucosal tissues. Previous BIS studies have been relied on hand-made probes possessing significan...

Reliable, automated, and user-friendly solutions for the identification of sleep stages in home environment are needed in various clinical and scientific research settings. Previously we have shown that signals recorded with an easily applicable textile electrode headband (FocusBand, T 2 Green Pty Ltd) contain characteristics similar to the standar...

In the above article [1] , Table 2 partially showed erroneous values for the absolute skin-electrode impedances while the correct median absolute impedances were presented in Figure 2. The authors regret the error and apologize for the possible inconvenience. The corrected Table 2 is presented below.

Artificial neural networks show great success in sleep stage classification, with an accuracy comparable to human scoring. While their ability to learn from labelled electroencephalography (EEG) signals is widely researched, the underlying learning processes remain unexplored. Variational autoencoders can capture the underlying meaning of data by e...

Objective: Obstructive sleep apnea (OSA) is diagnosed using the apnea-hypopnea index (AHI), which is the average number of respiratory events per hour of sleep. Recently, machine learning algorithms for automatic AHI assessment have been developed, but many of them do not consider the individual sleep stages or events. In this study, we aimed to d...

Background and objective Many sleep recording software used in clinical settings have some tools to automatically analyze the blood oxygen saturation (SpO2) signal by detecting desaturations. However, these tools are often inadequate for scientific research as they do not provide SpO2 signal-based parameters which are superior in the estimation of...

Objectives/Background Interest in using blood oxygen desaturations in the diagnostics of sleep apnea has risen in recent years. However, no standardized criteria for desaturation scoring exist which complicates the drawing of solid conclusions from literature. Patients/methods We investigated how different desaturation scoring criteria affect the...

Background: Obstructive sleep apnoea (OSA) causes, among other things, intermittent blood oxygen desaturations, increasing the sympathetic tone. Yet the effect of desaturations on heart rate variability (HRV), a simple and noninvasive method for assessing sympathovagal balance, has not been comprehensively studied. We aimed to study whether desatu...

We have previously developed an ambulatory electrode set (AES) for the measurement of electroencephalography (EEG), electrooculography (EOG), and electromyography (EMG). The AES has been proven to be suitable for manual sleep staging and self-application in in- home polysomnography (PSG). To further facilitate the diagnostics of various sleep disor...

Home sleep apnea testing (HSAT) without electroencephalography (EEG) recording is increasingly used as an alternative to in-laboratory polysomnography for the diagnosis of obstructive sleep apnea (OSA). However, without EEG, electrooculography (EOG), and chin electromyography (EMG) recordings, the OSA severity may be significantly underestimated. A...

The current clinically used electroencephalography (EEG) sensors are not self-applicable. This complicates the recording of the brain’s electrical activity in unattended home polysomnography (PSG). When EEG is not recorded, the sleep architecture cannot be accurately determined, which decreases the accuracy of home-based diagnosis of sleep disorder...

Near-infrared spectroscopy (NIRS) is a non-ionizing optical technique that can be used to quantify proteins, carbohydrates, fats, and other organic and biological substances. The aim of this study was to determine the ability of NIRS to identify different concentrations of L-fucose and L-proline solutions by utilizing different NIR spectral regions...

Objective: We aimed to investigate the differences in electroencephalogram (EEG) gamma power (30-40 Hz) of respiratory arousals between varying types and severities of respiratory events, and in different sleep stages. Methods: Power spectral densities of EEG signals from diagnostic Type I polysomnograms of 869 patients with clinically suspected...

In this study, FocusBand’s textile electrodes were tested against medical-grade wet electrodes to investigate the possible differences in skin-electrode interface behavior and EEG signals’ quality. In vivo electrical impedance spectroscopy and simultaneous forehead EEG measurements were performed with ten healthy subjects. In addition, the FocusBan...

Saliva is a complex oral fluid, and plays a major role in oral health. Primary Sjögren’s syndrome (pSS), as an autoimmune disease that typically causes hyposalivation. In the present study, salivary metabolites were studied from stimulated saliva samples (n = 15) of female patients with pSS in a group treated with low-dose doxycycline (LDD), saliva...

Sleep disorders form a massive global health burden and there is an increasing need for simple and cost-efficient sleep recording devices. Recent machine learning-based approaches have already achieved scoring accuracy of sleep recordings on par with manual scoring, even with reduced recording montages. Simple and inexpensive monitoring over multip...

Intermittent hypoxaemia is a risk factor for numerous diseases. However, the reverse pathway remains unclear. Therefore, we investigated whether pre‐existing hypertension, diabetes or cardiovascular diseases are associated with the worsening of intermittent hypoxaemia. Among the included 2,535 Sleep Heart Health Study participants, hypertension (n...

We aimed to investigate differences in the electroencephalography (EEG) signal characteristics recorded with a type II polysomnography (PSG) setup including the American Academy of Sleep Medicine recommended EEG montage and Self Applied Somnography (SAS) setup. The PSG and SAS monitoring were simultaneously performed in a pediatric cohort (n=111) w...

Study Objectives To assess the relationship between obstructive sleep apnea (OSA) severity and sleep fragmentation, accurate differentiation between sleep and wakefulness is needed. Sleep staging is usually performed manually using electroencephalography (EEG). This is time-consuming due to complexity of EEG setup and the amount of work in manual s...

Study Objectives Obesity, older age, and male sex are recognized risk factors for sleep apnea. However, it is unclear whether the severity of hypoxic burden, an essential feature of sleep apnea, is associated with the risk of sleep apnea worsening. Thus, we investigated our hypothesis that the worsening of sleep apnea is expedited in individuals wi...

The diagnosis of obstructive sleep apnea is based on daytime symptoms and the frequency of respiratory events during the night. The respiratory events are scored manually from polysomnographic recordings, which is time-consuming and expensive. Therefore, automatic scoring methods could considerably improve the efficiency of sleep apnea diagnostics...

PurposeHypertension is a common finding in patients with obstructive sleep apnea (OSA), but it has remained unclear whether or not the amount of disturbed breathing and characteristics of individual respiratory events differ between hypertensive and normotensive patients with severe OSA.Methods Full polysomnographic recordings of 323 men and 89 wom...

Background Supine sleeping position and obesity are well-known risk factors for obstructive sleep apnea (OSA) and modulate the risk for OSA-related daytime sleepiness. Although respiratory event durations are associated with OSA-related severe health consequences, it is unclear how sleeping position, obesity, and daytime sleepiness affect respirato...

Purpose: To investigate inter- and intra-individual variation in the levels and outputs (concentration multiplied by salivary flow rate) of salivary metabolites in patients with primary Sjögren’s syndrome (pSS). Methods: A total of 56 samples of stimulated saliva were collected from 14 female pSS patients during four laboratory visits within 20 we...

Low long-term heart rate variability (HRV), often observed in obstructive sleep apnea (OSA) patients, is a known risk factor for cardiovascular diseases. However, it is unclear how the type or duration of individual respiratory events modulate ultra-short-term HRV and beat-to-beat intervals (RR intervals). We aimed to examine the sex-specific chang...

Traditional sleep staging with non-overlapping 30-second epochs overlooks multiple sleep-wake transitions. We aimed to overcome this by analyzing the sleep architecture in more detail with deep learning methods and hypothesized that the traditional sleep staging underestimates the sleep fragmentation of obstructive sleep apnea (OSA) patients. To te...

Purpose: Obstructive sleep apnea (OSA) is associated with increased risk for stroke, which is known to further impair respiratory functions. However, it is unknown whether the type and severity of respiratory events are linked to stroke or transient ischemic attack (TIA). Thus, we investigate whether the characteristics of individual respiratory e...

Current diagnostics of sleep apnea relies on the time-consuming manual analysis of complex sleep registrations, which is impractical for routine screening in hospitalized patients with a high probability for sleep apnea, e.g. those experiencing acute stroke or transient ischemic attacks (TIA). To overcome this shortcoming, we aimed to develop a con...

The diagnosis of oral potentially malignant disorders currently relies on histopathological examination of surgically removed biopsies causing pain and discomfort for the patient. We hypothe-sise that non-invasive bioimpedance spectroscopy (BIS) method would overcome these problems and could make possible regular screening of at-risk patients. Prev...

Purpose: To investigate inter- and intra-individual variation in the levels and outputs (concentration multiplied by salivary flow rate) of salivary metabolites in patients with primary Sjögren’s syndrome (pSS). Methods: A total of 56 samples of stimulated saliva were collected from 14 female pSS patients during four laboratory visits within 20 wee...

Bruxhome method for objective and accurate assessment of sleep bruxism at home

Objectives Besides hypoxemia severity, heart rate variability has been linked to cognitive decline in obstructive sleep apnea (OSA) patients. Thus, our aim was to examine whether the frequency domain features of nocturnal photoplethysmogram (PPG) can be linked to poor performance in psychomotor vigilance task (PVT). Methods PPG signals from 567 su...

Purpose To determine the accuracy of scoring masticatory muscle activity (MMA) events in seven different polysomnography (PSG) setups. Methods Nineteen volunteers (13 females, 6 males, age 31.1 ± 12.9 years, 12 self-proclaimed bruxers) attended one-night PSG recording, supplemented with audio, video, and a separate frontal electroencephalography e...

Background As nocturnal hypoxemia and heart rate variability are associated with excessive daytime sleepiness (EDS) related to OSA, we hypothesize that the power spectral densities (PSD) of nocturnal pulse oximetry signals could be utilized in the assessment of EDS. Thus, we aimed to investigate if PSDs contain features that are related to EDS and...

A common symptom of obstructive sleep apnea (OSA) is excessive daytime sleepiness (EDS). The gold standard test for EDS is the multiple sleep latency test (MSLT). However, due to its high cost, MSLT is not routinely conducted for OSA patients and EDS is instead evaluated using sleep questionnaires. This is problematic however, since sleep questionn...

Study Objectives Accurate identification of sleep stages is essential in the diagnosis of sleep disorders (e.g. obstructive sleep apnea, OSA) but relies on labor-intensive EEG-based manual scoring. Furthermore, long-term assessment of sleep relies on actigraphy differentiating only between wake and sleep periods without identifying specific sleep s...

Background Diagnostics of obstructive sleep apnea (OSA) is based on apnea-hypopnea index (AHI) determined as full-night average of occurred events. We investigate our hypothesis that intra-night variation in the frequency of obstructive events affects diagnostics and prognostics of OSA and should therefore be considered in clinical practice. Metho...

In response to the growing clinico-economic need for comprehensive home-based sleep testing, we recently developed a self-applicable facial electrode set with screen-printed Ag/AgCl electrodes. Our previous studies revealed that nocturnal sweating is a common problem, causing low-frequency artifacts in the measured electroencephalography (EEG) sign...

Early diagnosis is essential but challenging in severe sepsis. Quantifying and comparing metabolite concentrations in serum has been suggested as a new diagnostic tool. Here we used proton nuclear magnetic resonance spectroscopy (1H NMR) based metabolomics to analyze the possible differences in metabolite concentrations between sera taken from sept...

Current diagnostic parameters estimating obstructive sleep apnea (OSA) severity have a poor connection to the psychomotor vigilance of OSA patients. Thus, we aimed to investigate how the severity of apneas, hypopneas, and intermittent hypoxemia is associated with impaired vigilance. We retrospectively examined Type I polysomnography data and corres...

The identification of sleep stages is essential in the diagnostics of sleep disorders, among which obstructive sleep apnea (OSA) is one of the most prevalent. However, manual scoring of sleep stages is time-consuming, subjective, and costly. To overcome this shortcoming, we aimed to develop an accurate deep learning approach for automatic classific...

Oral mucosal diseases are common health problems that reduce overall wellbeing and increase the risk for several systemic diseases. Due to the limitations of present diagnostics, new non-invasive methods are needed for reliable, affordable, real-time screening and follow-up of oral mucosal lesions. Bioimpedance spectroscopy, spectral camera imaging...

University of Eastern Finland (UEF) researchers have developed a novel measuring arrangement (BruxHome, Fig. 1) which enables the reliable diagnostics of sleep bruxism at home. Since developed method is well suited for sleep staging, it could be also applicable to home sleep apnea testing (HSAT).

Sweat artefact tolerance of screen printed EEG sensors

The accurate diagnosis of sleep disorders requires an electroencephalography (EEG) recording. However, in-home EEG sleep monitoring has been hindered by the present cumbersome electrode systems which are impractical for patient self-application. To overcome this shortcoming, we recently introduced a self-applicable facial electrode set with screen-...

Apnea-hypopnea index (AHI) is determined as full night average and therefore hides the possible intra-night variations in OSA severity. In this study, we analyzed sleep recordings from 1989 patients with suspected OSA and calculated the number and severity of individual respiratory events first 6 hours of sleep. The frequency of respiratory events,...

Many oral diseases, such as oral leukoplakia and erythroplakia, which have a high potential for malignant transformations, cause abnormal structural changes in the oral mucosa. These changes are clinically assessed by visual inspection and palpation despite their poor accuracy and subjective nature. We hypothesized that non-invasive bioimpedance sp...

The analysis of the salivary metabolomic profile may offer an early phase approach to assess the changes associated with a wide range of diseases including head and neck cancer. The aim of the present study was to investigate the potential of nuclear magnetic resonance (NMR) spectroscopy for detecting the salivary metabolic changes associated with...

Study objectives: To examine the presence of a first-night effect (FNE) and the level of internight variability in sleep bruxism (SB) activity when a self-applicable electrode set is used in home polysomnography (PSG) in a sample of subjects with possible SB. Methods: Fourteen females and two males aged 38.3 ± 9.1 years (mean ± standard deviatio...

Using sleep laboratory polysomnography (PSG) is restricted for the diagnosis of only the most severe sleep disorders due to its low availability and high cost. Home PSG is more affordable, but applying conventional electroencephalography (EEG) electrodes increases its overall complexity and lowers the availability. Simple, self-administered single-...

Currently, definite diagnosis of sleep bruxism requires polysomnography. However, it is restrictedly available, and too cumbersome and expensive for the purpose. The aim of this study was to introduce an ambulatory electrode set and evaluate its feasibility for more cost-effective diagnostics of sleep bruxism. Six self-assessed bruxers (one male, f...

Obstructive sleep apnea (OSA) increases the risk of TIA and ischemic stroke, and it also worsens strokés rehabilitation outcomes. However, screening of OSA is not routinely performed in TIA or acute stroke. The aims were (i) to study the prevalence and severity of OSA with polygraphy (PG) in patients suffering from first TIA or acute ischemic strok...

Saliva provides a valuable tool for assessing oral and systemic diseases, but concentrations of salivary components are very small, calling the need for precise analysis methods. In this work, Fourier transform infrared (FT-IR) spectroscopy using transmission and photoacoustic (PA) modes were compared for quantitative analysis of saliva. The perfor...

Recently, a number of portable devices designed for full polysomnography at home have appeared. However, current scalp electrodes used for electroencephalograms are not practical for patient self-application. The aim of this study was to evaluate the suitability of recently introduced forehead electroencephalogram electrode set and supplementary ch...