Sleep

Sleep quality

Sleep is an essential recovery process in which the body replenishes energy stores and clears waste products. Disturbed sleep is associated with an increased risk of cardiovascular disease[1], metabolic disease[2], mental health problems[3], neurodegenerative disease[4] and higher all-cause mortality[5]. For cancer the picture is mixed: long sleep duration in particular seems to be associated with certain cancers, such as colorectal cancer[6].

Better sleep demonstrably improves how someone feels and functions, mentally too[3]. Whether it also prevents heart attacks or death has not been demonstrated.

Guidelines

Several meta-analyses show that the optimal sleep duration is 7 to 9 hours: both short sleep (less than 6 hours) and long sleep (more than 9 hours) are associated with an increased risk of chronic disease and mortality[7], [8], [9].

How Synapse assesses this

Synapse maps sleep health with the Mini Sleep Questionnaire (MSQ)[10], supplemented with the Insomnia Severity Index (ISI)[11]. The MSQ assesses both sleep quality at night and alertness during the day; the two dimensions are scored separately. The score per dimension combines MSQ and ISI and takes sleep duration into account: within the 7 to 9 hour window there is no correction, outside it the score falls, and sleeping too little weighs more heavily than sleeping too long. That combination is Synapse's own choice, not an externally validated composite. The result is a score from 0 to 100 with the general zone classification:

Sleep quality score (0-100)Assessment
> 75Optimal
50 to 75Acceptable
25 to 50Watch
< 25Priority

The rows (sleep medication, difficulty falling asleep, waking up too early, restless nights, difficulty falling back asleep, snoring) are frequencies; Synapse shows no reference value for them. Synapse also asks specifically about snoring and about night work or shift work.

Wake quality

Besides the night, the MSQ also assesses alertness during the day: difficulty staying awake, waking up tired, waking up with headaches, and feeling tired and sluggish[10]. Daytime sleepiness reflects both the quality and the duration of the night's sleep, and can point to sleep apnoea.

Guidelines

For screening for obstructive sleep apnoea, STOP-BANG is a common and practical questionnaire[12].

How Synapse assesses this

Synapse scores wake quality separately from sleep quality, in the same way: a combination of MSQ and ISI with a correction for sleep duration, and the same zone classification from 0 to 100. For the rows Synapse shows no reference value.

To estimate sleep apnoea, Synapse uses a question set based on STOP-BANG[12], in which neck circumference is replaced by the waist-to-height ratio, because abdominal fat is strongly associated with obstructive sleep apnoea[13]. Published cut-offs for that ratio in sleep apnoea lie around 0.575 in men and 0.595 in women[14]. This adapted version has not been externally validated, so the published test characteristics of the original STOP-BANG do not apply to it unreservedly.

Symptom and outcome

Better sleep demonstrably improves how someone feels and functions during the day[3]. Whether treating sleep problems or sleep apnoea also prevents heart attacks or death has not been demonstrated.

Developed and reviewed with the Synapse medical advisory board.

References

  1. [1]Pan, Y. et al. The association between sleep deprivation and the risk of cardiovascular diseases: a systematic meta-analysis. Biomed Rep 19, 78 (2023). doi.org/10.3892/br.2023.1660
  2. [2]Che, T. et al. The association between sleep and metabolic syndrome: a systematic review and meta-analysis. Front Endocrinol (Lausanne) 12, 773646 (2021). doi.org/10.3389/fendo.2021.773646
  3. [3]Scott, A. J. et al. Improving sleep quality leads to better mental health: a meta-analysis of randomised controlled trials. Sleep Med Rev 60, 101556 (2021). doi.org/10.1016/j.smrv.2021.101556
  4. [4]Bubu, O. M. et al. Sleep, cognitive impairment, and Alzheimer's disease: a systematic review and meta-analysis. Sleep 40, zsw032 (2017). doi.org/10.1093/sleep/zsw032
  5. [5]Shen, X. et al. Nighttime sleep duration, 24-hour sleep duration and risk of all-cause mortality among adults: a meta-analysis of prospective cohort studies. Sci Rep 6, 21480 (2016). doi.org/10.1038/srep21480
  6. [6]Zhao, H. et al. Sleep duration and cancer risk: a systematic review and meta-analysis of prospective studies. Asian Pac J Cancer Prev 14, 7509–7515 (2013). doi.org/10.7314/apjcp.2013.14.12.7509
  7. [7]Hirshkowitz, M. et al. National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep Health 1, 40–43 (2015). doi.org/10.1016/j.sleh.2014.12.010
  8. [8]Itani, O. et al. Short sleep duration and health outcomes: a systematic review, meta-analysis, and meta-regression. Sleep Med 32, 246–256 (2017). doi.org/10.1016/j.sleep.2016.08.006
  9. [9]Jike, M. et al. Long sleep duration and health outcomes: a systematic review, meta-analysis and meta-regression. Sleep Med Rev 39, 25–36 (2018). doi.org/10.1016/j.smrv.2017.06.011
  10. [10]Natale, V. et al. Psychometric goodness of the Mini Sleep Questionnaire. Psychiatry Clin Neurosci 68, 568–573 (2014). doi.org/10.1111/pcn.12161
  11. [11]Morin, C. M. et al. The Insomnia Severity Index: psychometric indicators to detect insomnia cases and evaluate treatment response. Sleep 34, 601–608 (2011). doi.org/10.1093/sleep/34.5.601
  12. [12]Chung, F. et al. STOP-Bang questionnaire: a practical approach to screen for obstructive sleep apnea. Chest 149, 631–638 (2016). doi.org/10.1378/chest.15-0903
  13. [13]Santos, R. B. et al. Accuracy of global and/or regional anthropometric measurements of adiposity in screening sleep apnea: the ELSA-Brasil cohort. Sleep Med 63, 115–121 (2019). doi.org/10.1016/j.sleep.2019.04.020
  14. [14]Unal, Y. et al. Association between obstructive sleep apnea syndrome and waist-to-height ratio. Sleep Breath 23, 523–529 (2019). doi.org/10.1007/s11325-018-1725-4

Put it into practice

Sleep