Improve Sleep Consistency

Sleep consistency — regularity of sleep and wake timing — is a more powerful predictor of health outcomes than total sleep duration alone. Research consistently shows that irregular sleep timing disrupts the circadian rhythm, which governs metabolism, immune function, hormonal regulation, and cognitive performance. The most important metric is sleep timing variability: how much do your actual bedtime and wake time vary day to day? Establish a 14-day baseline (14 days rather than 7 captures the full weekly cycle including weekend variation, which is the most common source of inconsistency). Record each morning: actual time you fell asleep (as close as you can estimate), actual wake time, and total sleep duration in hours. Calculate the variability across the 14 days: the range from earliest to latest bedtime (in hours and minutes), the range from earliest to latest wake time, and the average total sleep duration. The NHS recommends 7–9 hours for adults. Social jet lag — the shift between weekday and weekend sleep timing — is particularly important; note if your weekend sleep timing differs from your weekday timing by more than 1 hour.