Browsing by Subject "Social jet lag"

Now showing 1 - 3 of 3
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    Living at the wrong time: effects of unmatching official time in Portugal and western Spain
    (MDPI, 2022-07-28) Casado Ramírez, Elvira; Moreno Casbas, María Teresa; Campos Martínez, Manuel; ModulEN Consortium; Madrid, Juan Antonio; Rol de Lama, María de los Ángeles; Bonmatí Carrión, María de los Ángeles; Fisiología
    Human circadian rhythmicity is subjected to the internal circadian clock, the sun and social clocks (official time, social/work schedules). The discrepancy among these clocks, as occurs when official time does not match its geographical time zone, may produce circadian disruption. Western Spain (GMT+1/+2) and Portugal (GMT0/+1) share similar longitudes (sun time) but have different official times. This provides a unique opportunity to evaluate the effects of official time on circadian rhythmicity and sleep in elderly and retired populations (with no remunerated duties presumed, although other social commitments may be present) at both locations. Although both populations slept enough for their age (7–8 h), circadian robustness (e.g., interdaily stability, relative amplitude) was greater in Portugal, especially during weekdays, while greater desynchronization (both body temperature vs. motor activity and body temperature vs. light exposure) tended to occur in the Spaniards. Once corrected by GMT0, meals took place later in Spain than in Portugal, especially as the day progresses, and a possible interplay between bed/meal timings and internal desynchronization was found. Our results point to the possible deleterious effect on circadian system robustness when official time is misaligned with its geographical time zone.
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    Optimal nap timing and body mass index: beyond duration
    (BioMed Central, 2026-04-01) Longo Silva, Giovana; Rodríguez Martín, María; Salmerón Martínez, Diego; Scheer, Frank A. J. L.; Garaulet Aza, Marta; Fisiología; Facultades de la UMU::Facultad de Biología
    Background Overweight and obesity continue to rise globally, and sleep has emerged as an important behavioral determinant of body weight. While nighttime sleep has been widely studied, the role of daytime napping—especially nap timing—remains unclear. Existing research relies on clock time, which may not reflect individual rhythms. This study investigates whether nap timing referenced to daily events is associated with BMI in two adult populations of habitual nappers (Spain and Brazil). Secondary aims included the association of nap duration and weekend–weekday differences in nap timing and duration with BMI. Methods Habitual nappers (n = 3550) aged 18–65 years were studied. Nap timing was calculated relative to wake time and lunch time. As secondary analyses, nap duration and weekend–weekday differences in nap timing (nap jet lag) and in nap duration were evaluated. Linear regression and restricted cubic spline models were applied. Results BMI and excess weight prevalence were similar between countries. Compared with Spaniards, Brazilians showed earlier naps (by >2 h), longer weekend naps (by 13 min), and greater nap jet lag (by 23 min) (all p < 0.001). Despite these differences, no significant interactions by country were observed in nap–BMI associations, and data were pooled. Nap timing relative to wake and lunch displayed L-shaped associations with BMI: the highest BMI corresponded to early naps (~3h after waking and ~2h before lunch), whereas the lowest BMI (i.e. the inflection points) occurred when naps were 7h18min after wake (β = −0.48 kg/m2 per hour before the inflection point, p = 0.001) and 1h15min after lunch (β = −0.53 kg/m2 per hour before the inflection point, p = 0.031). Shorter and more consistent nap duration across the week was associated with lower BMI (p < 0.05). Conclusions Findings highlight nap timing as a novel behavioral factor associated with BMI, warranting further longitudinal research to explore its potential causal role.
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    Publication
    Open Access
    Optimal nap timing and body mass index: beyond duration
    (BioMed Central, 2026-04-01) Longo-Silva, Giovana; Rodríguez Martín, María; Salmerón Martínez, Diego; Scheer, Frank A. J. L.; Garaulet Aza, Marta; Ciencias Sociosanitarias; Facultad de Medicina
    Background: Overweight and obesity continue to rise globally, and sleep has emerged as an important behavioral determinant of body weight. While nighttime sleep has been widely studied, the role of daytime napping—especially nap timing—remains unclear. Existing research relies on clock time, which may not reflect individual rhythms. This study investigates whether nap timing referenced to daily events is associated with BMI in two adult populations of habitual nappers (Spain and Brazil). Secondary aims included the association of nap duration and weekend–weekday differences in nap timing and duration with BMI. Methods: Habitual nappers (n = 3550) aged 18–65 years were studied. Nap timing was calculated relative to wake time and lunch time. As secondary analyses, nap duration and weekend–weekday differences in nap timing (nap jet lag) and in nap duration were evaluated. Linear regression and restricted cubic spline models were applied. Results: BMI and excess weight prevalence were similar between countries. Compared with Spaniards, Brazilians showed earlier naps (by >2 h), longer weekend naps (by 13 min), and greater nap jet lag (by 23 min) (all p < 0.001). Despite these differences, no significant interactions by country were observed in nap–BMI associations, and data were pooled. Nap timing relative to wake and lunch displayed L-shaped associations with BMI: the highest BMI corresponded to early naps (~3h after waking and ~2h before lunch), whereas the lowest BMI (i.e. the inflection points) occurred when naps were 7h18min after wake (β = −0.48 kg/m2 per hour before the inflection point, p = 0.001) and 1h15min after lunch (β = −0.53 kg/m2 per hour before the inflection point, p = 0.031). Shorter and more consistent nap duration across the week was associated with lower BMI (p < 0.05). Conclusions: Findings highlight nap timing as a novel behavioral factor associated with BMI, warranting further longitudinal research to explore its potential causal role.