Focus on sleep-related breathing disorders.

Abstract

Dear members of the ESRS, Dear readers of JSR, The fifth issue of JSR in 2019 brings together a variety of articles from sleep research and sleep medicine. A major focus this time is the field of sleep-related breathing disorders, mirrored by 17 articles on this topic in this issue. This, in my opinion, reflects the liveliness and ongoing research interest of this subspecialty of sleep medicine. Included articles range from more basic oriented questions to pure clinical issues comparing different therapeutic modalities in sleep apnea. Other work in this issue focuses on sleep in neurological conditions, sleep and cognitive function, sleep and motor systems, dreaming, sleep in couples, sleep and learning and sleep restriction. Future issues will more specifically focus on other subspecialties of sleep medicine, such as insomnia, mental disorders or restless legs syndrome. I would like to highlight four of the articles in this issue. Lee, Choi, Chang, Kim, and Shin (2019) report data from a 14-year follow-up study that examined the independent association between self-reported snoring and the incidence of hypertension by age and gender in a large cohort of Korean citizens. Almost 5,000 adults between the ages of 40 and 69, being free of hypertension at baseline, were included. The sample was divided on the basis of self-reported snoring frequency on a scale from never to habitual snorer (snoring ≥4 nights). At biennial follow-up visits, blood pressure was measured by trained examiners. Altogether, 14 years were followed-up after the first investigation. The main result was that after adjusting for known cardiovascular risk factors only men aged ≤45 years with habitual snoring showed a significantly increased risk (1.5 times higher) of incident hypertension compared with those who never snored. This relationship was independent of the presence of excessive daytime sleepiness. In women, no such relationship was found. The authors conclude from their study that young male snorers may be at an increased risk of future development of hypertension, which seems to have important clinical implications for the early detection and treatment of snoring, in order to reduce the burden of cardiovascular disease. Another paper from this field looked at social inequalities in sleep-disordered breathing (Petrovic et al., 2019). Data were taken from the so-called CoLaus/HypnoLaus study, a study that included more than 2,000 participants from Lausanne in Switzerland. Data were collected on hypopnea and oxygen desaturation indices, and on lifestyle-related factors, and BMI and socioeconomic status were measured through several variables. The authors were able to show that lower occupation and lower education were associated with a higher apnea–hypopnea index and number of oxygen desaturations. Furthermore, BMI was associated with socioeconomic status and breathing measures and contributed to the socioeconomic gradient in sleep-disordered breathing. The authors conclude that low socioeconomic status is a risk factor for sleep-disordered breathing, which is partly explained by BMI. This is an important result, which underlines that social differences may contribute to this widespread sleep disorder and may help to implement strategies to identify high-risk profiles for sleep-disordered breathing. We have to face the fact that, as in many other disorders/diseases, sleep disorders may be influenced by socioeconomic factors, a fact that is frequently overlooked. Broström, Pakpour, Nilsen, Hedberg, and Ulander (2019) from Sweden report on two short questionnaires that aim to measure shared decision making during initiation of CPAP treatment. This is an important issue because adherence or non-adherence to CPAP is a major clinical issue in the field of sleep-disordered breathing. Both applied questionnaires provided good validity and reliability scores to measure shared decision making and decisional conflict in relation to CPAP initiations. It was shown that decisional conflict and low shared decision making had an impact on CPAP use. Thus, the authors suggest that their questionnaires should be used by healthcare personnel as a tool to simplify the assessment of shared decision making. Malinowski, Carr, Edwards, Ingarfill, and Pinto (2019) present data from the field of dreaming. They follow the exciting theoretic assumption that especially dreaming during REM sleep may lead to a rebound of suppressed thoughts in dream content. They call this phenomenon the dream rebound effect. They performed an experimental investigation to study this hypothesis by randomly assigning participants to a pleasant or unpleasant thought suppression condition for 5 min pre-sleep every evening. Dreams were collected every morning for the next 7 days, and it was found that unpleasant thoughts were more prone to dream rebound than pleasant thoughts. Furthermore, it was found that dream rebound and successful suppression both have positive effects on subjective emotional responses to pleasant and unpleasant thoughts. According to the authors, their results provide further support for a positive emotion-processing theory of dream function.