Sleep Score Scientific Reference

Sahha's Sleep Score integrates several critical dimensions of sleep health, including sleep duration, sleep regularity, sleep continuity, sleep efficiency, sleep debt, circadian alignment, physical recovery, and mental recovery. By providing a comprehensive measure of these factors, the Sleep Score aims to encourage users to adopt healthier sleep behaviours.

Score Design

The Sleep Score is derived by factors, each of which is weighted slightly differently based on the research of the importance of that factor to overall sleep health.

Each factor is normalised to account for the differences in distribution across the various aspects of sleep health. The score is on a scale of 0 to 100, with higher scores indicating greater overall sleep health.

Sleep Factors: Key Constituents of Sleep

The Sleep Score incorporates multiple factors that define an individual’s movement throughout the day. Here’s a breakdown of each factor and its contribution to the final score:

Sleep Duration: Sleep duration is a fundamental metric in sleep research, as it directly influences numerous aspects of health. Consistent evidence links inadequate sleep duration to a range of negative health outcomes, including metabolic, cardiovascular, and cognitive impairments. Research has demonstrated that optimal sleep duration (generally 7-9 hours for adults) is crucial for maintaining overall health and reducing mortality risk ( Cappuccio et al., 2010 )
Sleep Regularity: Regular sleep patterns are essential for maintaining stable circadian rhythms, which regulate a variety of physiological processes including hormone release, metabolism, and mood. Irregular sleep schedules have been shown to disrupt these rhythms, leading to adverse effects on both mental and physical health.
Sleep Continuity: Sleep continuity, or the ability to maintain uninterrupted sleep throughout the night, is critical for the restorative functions of sleep. Disrupted sleep is linked to impairments in cognitive function, emotional regulation, and physical health. Studies show that continuous sleep, particularly during the deeper stages of sleep, is necessary for effective recovery processes.
Sleep Debt: Sleep debt refers to the cumulative effect of not getting enough sleep over time. Research indicates that chronic sleep deprivation leads to long-term health issues, such as cardiovascular disease, obesity, and decreased cognitive function. Addressing sleep debt is crucial for preventing these adverse outcomes ( Van Dongen et al., 2003 )
Circadian Alignment: Circadian alignment, which ensures that sleep occurs in sync with the body’s natural biological clock, is vital for optimizing health. Misalignment, often due to shift work or irregular sleep patterns, has been associated with a variety of metabolic, cardiovascular, and psychological disorders. ( Scheer et al., 2009 )
Physical Recovery (REM Sleep): REM sleep is essential for physical recovery, particularly in relation to the repair of tissues, muscle growth, and the maintenance of the immune system. The distribution and amount of REM sleep are critical in ensuring that the body recovers effectively, especially after physical exertion.
Mental Recovery (Deep Sleep): Deep sleep, or slow-wave sleep (SWS), plays a pivotal role in mental recovery. It is during this stage that processes such as memory consolidation, emotional regulation, and cognitive maintenance occur ( Rasch and Born, 2013 ). Sufficient deep sleep is necessary for optimal cognitive performance and mental health.

Normalization and Adjustments

The Activity Score is normalized to account for differences in fitness levels and demographics. For example, older adults may have a different step goal or calorie burn threshold compared to younger adults. This ensures that the score reflects individual health needs rather than a one-size-fits-all target.

References

Cappuccio, F. P., D'Elia, L., Strazzullo, P., & Miller, M. A. (2010). Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep , 33(5), 585-592.

Dworak, M., Diel, P., Voss, S., Hollmann, W., & Strüder, H. K. (2007). Intense exercise increases sleep spindles and the amount of slow-wave sleep in humans. European Journal of Applied Physiology , 99(1), 79-89

Ohayon, M. M., & Carskadon, M. A. (2013). Sleep debt, circadian rhythms, and performance: implications for fatigue management. Sleep Medicine Reviews , 17(5), 367-376.

Phillips, A. J., Clerx, W. M., O'Brien, C. S., Sano, A., Barger, L. K., Picard, R. W., ... & Czeisler, C. A. (2017). Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing. Scientific Reports , 7(1), 1-13.

Rasch, B., & Born, J. (2013). About sleep's role in memory. Physiological Reviews , 93(2), 681-766.

Scheer, F. A., Hilton, M. F., Mantzoros, C. S., & Shea, S. A. (2009). Adverse metabolic and cardiovascular consequences of circadian misalignment. Proceedings of the National Academy of Sciences , 106(11), 4453-4458.