Browsing by Author "Tkachev, Vadim"
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- Estimation bias and agreement limits between two common self-report methods of habitual sleep duration in epidemiological surveysPublication . Korman, Maria; Zarina, Daria; Tkachev, Vadim; Merikanto, Ilona; Bjorvatn, Bjørn; Bjelajac, Adrijana Koscec; Penzel, Thomas; Landtblom, Anne Marie; Benedict, Christian; Chan, Ngan Yin; Wing, Yun Kwok; Dauvilliers, Yves; Morin, Charles M.; Matsui, Kentaro; Nadorff, Michael; Bolstad, Courtney J.; Chung, Frances; Mota-Rolim, Sérgio; Gennaro, Luigi De; Plazzi, Giuseppe; Yordanova, Juliana; Holzinger, Brigitte; Partinen, Markku; Reis, CátiaAccurate measurement of habitual sleep duration (HSD) is crucial for understanding the relationship between sleep and health. This study aimed to assess the bias and agreement limits between two commonly used short HSD self-report methods, considering sleep quality (SQ) and social jetlag (SJL) as potential predictors of bias. Data from 10,268 participants in the International COVID Sleep Study-II (ICOSS-II) were used. Method-Self and Method-MCTQ were compared. Method-Self involved a single question about average nightly sleep duration (HSDself), while Method-MCTQ estimated HSD from reported sleep times on workdays (HSDMCTQwork) and free days (HSDMCTQfree). Sleep quality was evaluated using a Likert scale and the Insomnia Severity Index (ISI) to explore its influence on estimation bias. HSDself was on average 42.41 ± 67.42 min lower than HSDMCTQweek, with an agreement range within ± 133 min. The bias and agreement range between methods increased with poorer SQ. HSDMCTQwork showed less bias and better agreement with HSDself compared to HSDMCTQfree. Sleep duration irregularity was − 43.35 ± 78.26 min on average. Subjective sleep quality predicted a significant proportion of variance in HSDself and estimation bias. The two methods showed very poor agreement and a significant systematic bias, both worsening with poorer SQ. Method-MCTQ considered sleep intervals without adjusting for SQ issues such as wakefulness after sleep onset but accounted for sleep irregularity and sleeping in on free days, while Method-Self reflected respondents’ interpretation of their sleep, focusing on their sleep on workdays. Including an SQ-related question in surveys may help bidirectionally adjust the possible bias and enhance the accuracy of sleep-health studies.
- Outdoor daylight exposure and longer sleep promote wellbeing under COVID‐19 mandated restrictionsPublication . Korman, Maria; Tkachev, Vadim; Reis, Cátia; Komada, Yoko; Kitamura, Shingo; Gubin, Denis; Kumar, Vinod; Roenneberg, TillLight is an important regulator of daily human physiology in providing time-of-day information for the circadian clock to stay synchronised with the 24-hr day. The coronavirus disease 2019 (COVID-19) pandemic led to social restrictions in many countries to prevent virus spreading, restrictions that dramatically altered daily routines and limited outdoor daylight exposure. We previously reported that sleep duration increased, social jetlag decreased, and mid-sleep times delayed during social restrictions (Global Chrono Corona Survey, N = 7,517). In the present study, we investigated in the same dataset changes in wellbeing and their link to outdoor daylight exposure, and sleep–wake behaviour. In social restrictions, median values of sleep quality, quality of life, physical activity and productivity deteriorated, while screen time increased, and outdoor daylight exposure was reduced by ~58%. Yet, many survey participants also reported no changes or even improvements. Larger reductions in outdoor daylight exposure were linked to deteriorations in wellbeing and delayed mid-sleep times. Notably, sleep duration was not associated with outdoor daylight exposure loss. Longer sleep and decreased alarm-clock use dose-dependently correlated with changes in sleep quality and quality of life. Regression analysis for each wellbeing aspect showed that a model with six predictors including both levels and their deltas of outdoor daylight exposure, sleep duration and mid-sleep timing explained 5%–10% of the variance in changes of wellbeing scores (except for productivity). As exposure to daylight may extenuate the negative effects of social restriction and prevent sleep disruption, public strategies during pandemics should actively foster spending more daytime outdoors.