How strong is the evidence for Sleep Regularity?

Sleep regularity has emerged as an active and increasingly well-supported area of research, with recent large cohort studies (UK Biobank, MESA) finding that day-to-day consistency of sleep timing predicts cardiovascular disease and mortality risk, in some analyses more strongly than sleep duration itself. That evidence is currently rated moderate (66/100), built on 7 published studies -- a reasonable base, but not yet enough for full certainty.