Re-scoping ultradian rhythms in the context of metabolism.

Rapid, ultradian biological rhythms are only partly comparable to circadian (24-h) rhythms. Often, the ensuing expectations from this comparison are that 1) ultradian rhythms should be driven by discrete oscillators, 2) they are biochemically buffered, and 3) they must be functionally linked to extrinsic events and cycles. These three expectations are not always met, but perhaps there is an adaptive benefit to ultradian rhythms not meeting these expectations, which sets them functionally apart from circadian rhythms.

Physical Activity, Sleeping Problems, Weight, Feelings of Social Isolation, and Quality of Life of Older Adults After Coronavirus Infection: A Longitudinal Cohort Study.

Background: There is debate as to whether a coronavirus infection (SARS-CoV-2) affects older adults' physical activity, sleeping problems, weight, feelings of social isolation, and quality of life (QoL). We investigated differences in these outcomes between older adults with and without coronavirus infection over 180 days following infection.

Methods: We included 6789 older adults (65+) from the Lifelines COVID-19 cohort study who provided data between April 2020 and June 2021.

Co-expression of diurnal and ultradian rhythms in the plasma metabolome of common voles (Microtus arvalis).

Metabolic rhythms include rapid, ultradian (hourly) dynamics, but it remains unclear what their relationship to circadian metabolic rhythms is, and what role meal timing plays in coordinating these ultradian rhythms in metabolism. Here, we characterized widespread ultradian rhythms under ad libitum feeding conditions in the plasma metabolome of the vole, the gold standard animal model for behavioral ultradian rhythms, naturally expressing ~2-h foraging rhythms throughout the day and night. These ultradian metabolite rhythms co-expressed with diurnal 24-h rhythms in the same metabolites and did not align with food intake patterns.

Chronotype and environmental light exposure in a student population.

In humans and most other species, changes in the intensity and duration of light provide a critical set of signals for the synchronisation of the circadian system to the astronomical day. The timing of activity within the 24 h day defines an individual's chronotype, i.e.