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Sleep wakeups

Sleep Wake-ups Patterns and Mortality Risks

Sleep disruptions and irregular sleep patterns are significantly associated with increased mortality risk. Research consistently demonstrates that sleep quality, timing, and stability play crucial roles in long-term health outcomes. This report synthesizes current evidence on the relationship between various sleep wake-up patterns and mortality risk.

Sleep Fragmentation and Wake-ups

Impact on Mortality

Sleep fragmentation—characterized by frequent awakenings during the night—shows particularly strong associations with mortality risk:

  • Greater sleep fragmentation is associated with a significantly increased risk of mortality, with adjusted odds ratios of 2.19 (95% CI: 1.16-4.12) per 10-unit increase in fragmentation index1
  • Wake after sleep onset (WASO), which measures time spent awake during the night, is associated with higher mortality (OR = 1.24, 95% CI: 1.04-1.49, per 10-min increase)1
  • Lower percent sleep time (more interruptions) is associated with greater mortality risk (OR = 0.40, 95% CI: 0.17-0.92, per 10-percent increase)1

These associations remain significant even after adjusting for factors like age, sex, education, BMI, and sleep time preference, suggesting that sleep fragmentation is an independent risk factor for mortality.

Specific Sleep Disruptions

Various types of sleep disruptions show distinct relationships with mortality:

  • Difficulty initiating sleep (HR, 1.44; 95% CI, 1.20–1.72) and difficulty falling back asleep after waking (HR, 1.56; 95% CI, 1.29–1.89) are both associated with greater all-cause mortality risk2
  • Concurrent sleep difficulties show even stronger associations with mortality (HR, 1.80; 95% CI, 1.44–2.24)2
  • Difficulty maintaining alertness during the day ("Some Days": HR = 1.49; "Most/Every Day": HR = 1.65) and frequent daytime napping ("Most/Every Day": HR = 1.73) are also associated with increased mortality risk2

Sleep Regularity and Timing

Sleep Regularity Index

Sleep regularity—the consistency of sleep-wake timing from day to day—is strongly associated with mortality risk:

  • Irregular sleep-wake patterns show a robust association with higher mortality risk34
  • Those with the lowest sleep regularity (5th percentile, SRI = 41) had a 53% higher mortality risk compared to those with median regularity (HR 1.53, 95% CI: 1.41, 1.66)3
  • Similar patterns were observed for both cardiovascular disease and cancer mortality3
  • A "regular-optimal" sleep pattern (7.0 ± 1.0 hours obtained regularly) was associated with a 39% lower mortality hazard than an "irregular-insufficient" pattern (5.8 ± 1.4 hours with twice the irregularity)5

Sleep Timing

The timing of sleep also significantly impacts mortality risk:

  • A U-shaped association exists between bedtime and all-cause mortality6
  • Bedtime at 11:00 pm and waking up at 7:00 am was associated with the lowest all-cause and cardiovascular disease mortality risks6
  • Late bedtime (>12:00 am) increased all-cause mortality risk (HR 1.53, 95% CI 1.28-1.84)6
  • Late wake-up time (>8:00 am) was associated with increased all-cause mortality (HR 1.39, 95% CI 1.13-1.72)6
  • Delaying sleep midpoint (>4:00 am) was significantly associated with increased all-cause mortality6

Contextual Factors Affecting Sleep-Mortality Relationships

Sleep Duration

Sleep duration interacts with wake-up patterns to affect mortality risk:

  • Short sleep (<5h per night) is associated with a 12% greater mortality risk, while long sleep (>8 or 9h per night) carries a 30% greater risk compared to 7-8 hours7
  • Very short sleep duration (≤5 hours) shows particularly high mortality risk (HR = 2.38, 95% CI: 1.44–3.92)2
  • Stable patterns of both short and long sleep duration over time show stronger associations with mortality than fluctuating patterns8

Age and Sex Differences

The impact of sleep disruptions on mortality may vary by demographic factors:

  • Early morning waking appears to increase risk of CVD mortality specifically in Europeans, suggesting potential ethnic differences in the sleep-mortality relationship9
  • For short sleep, mortality effects are comparable between men and women, but for long sleep, estimates are stronger in older cohorts7

Conclusion

Sleep wake-up patterns—including fragmentation, timing, and regularity—significantly impact mortality risk. The evidence consistently shows that:

  1. Frequent nighttime awakenings and greater sleep fragmentation are associated with substantially increased mortality risk
  2. Irregular sleep-wake timing is associated with higher mortality risk from all causes, cardiovascular disease, and cancer
  3. Optimal sleep timing (bedtime around 11:00 pm and wake time around 7:00 am) is associated with the lowest mortality risk
  4. Combined factors (regular patterns with optimal duration) appear to provide the greatest protection against premature mortality

These findings highlight the importance of not only adequate sleep duration but also sleep quality, consistency, and appropriate timing in reducing mortality risk. Interventions targeting improved sleep regularity and reduced fragmentation may have significant potential to enhance longevity.

Footnotes

  1. https://pmc.ncbi.nlm.nih.gov/articles/PMC8271128/ ↩ ↩2 ↩3

  2. https://journals.sagepub.com/doi/10.1177/13872877241297111 ↩ ↩2 ↩3 ↩4

  3. https://pmc.ncbi.nlm.nih.gov/articles/PMC10153326/ ↩ ↩2 ↩3

  4. https://elifesciences.org/articles/88359 ↩

  5. https://onlinelibrary.wiley.com/doi/abs/10.1111/jsr.14048 ↩

  6. https://jcsm.aasm.org/doi/10.5664/jcsm.10926 ↩ ↩2 ↩3 ↩4 ↩5

  7. https://pmc.ncbi.nlm.nih.gov/articles/PMC2864873/ ↩ ↩2

  8. https://pubmed.ncbi.nlm.nih.gov/17969458/ ↩

  9. https://www.ucl.ac.uk/news/2019/jun/early-waking-linked-heart-disease-deaths-white-europeans ↩