By Kenzie MacDonald,


Based on reports from the American Academy of Sleep Medicine (AASM), the National Institute of Health recommends that adults over the age of 18 get 7-8 hours of sleep a night in order to feel refreshed.1 Although we may be aware or these recommendations, it has been reported that nearly one-third of Canadian adults get less than 6 hours of sleep a night.2 While the short-term ramifications of inadequate sleep, such as altered mood, judgment, memory, and information retention, are undeniably significant, over an extended period of time, sleep deprivation is also associated with a variety of severe health consequences.3 Specifically, chronic sleep deprivation and poor sleep quality have been correlated to health problems such as hypertension, obesity, diabetes, cancer, cardiovascular disease, and premature mortality in otherwise healthy individuals (i.e. those without primary sleep disorders).3-4

Sleep duration exhibits a particularly strong association to mortality risk, with short and long duration sleepers possessing greater risk than mid-duration (7-8 hours) sleepers.5 As well, when compared to mid-duration (7-8 hours) sleepers, short sleepers (≤6 hours) exhibit a 15% and 23% greater risk of developing cardiovascular disease and coronary heart disease, respectively.5 One of the mechanisms by which sleep duration is suggested to be associated with adverse cardiovascular health is through inflammation.5 Specifically, recent literature has indicated that sleep deprivation is associated with the pro-inflammatory processes that stimulate atherosclerotic plaque development.5 With the relationship between sleep and the pathogenesis of cardiovascular disease only recently recognized, making definitive conclusions about this process is not yet realistic.6

While the correlation between sleep duration and cardiovascular disease is more firmly established, a growing body of literature also suggests that those who alter their sleep regularity exhibit poorer overall health.7 This new research has specifically focused on those individuals that go to sleep later and wake up later on ‘free days’ than they do on ‘work days’.7 This phenomenon, which has been coined ‘social jet lag’, is a measure of the discrepancy between our internal clock and external environment on the days where sleep regularity is neglected.8 Similar to travel-induced jet lag, this discrepancy causes a misalignment of the circadian system.8

The circadian system is responsible for regulating important bodily functions, such as sleep-wake cycles, hormone release, and body temperature.9 This regulation of physical, mental, behavioral, and physiological processes over a 24-hour period is achieved through continuous assessment and integration of external and internal cues.10 While travel-induced jet lag temporarily disrupts the circadian system, social jet lag is particularly detrimental since it chronically disrupts one’s circadian rhythms.8 New research based on the analysis of 984 adults between 22 and 60 years of age indicated that one-hour of social jet lag was associated with an 11.1% increased risk of developing heart disease.7 These findings illustrate that, along with sleep duration, sleep regularity can also have a significant impact on the quality of our health.7



  1. National Institute of Health: National Heart, Lung, and Blood Institute. (2017). How much sleep is enough? Retrieved from
  2. CBC News. (2011, March 18). Lack of sleep called ‘global epidemic’. CBC News. Retrieved from
  3. Division of Sleep Medicine at Harvard Medical School. (n.d.). Consequences of insufficient sleep. Retrieved from
  4. Centers for Disease Control and Prevention. (2015). Insufficient sleep is a public health problem. Retrieved from
  5. Grandner, M. A., Sands-Lincoln, M. R., Pak, V. M., & Garland, S. N. (2013). Sleep duration, cardiovascular disease, and proinflammatory biomarkers. Nature and Science of Sleep, 5, 93-107.
  6. Wolk, R., Gami, A. S., Garcia-Touchard, A., & Somers, V. K. (2005). Sleep and cardiovascular disease. Current Problems in Cardiology, 30(12), 625-662.
  7. Sandoiu, A. (2017, June 5). Going to be later on weekends may harm your health. Medical News Today. Retrieved from
  8. Parsons, M., Moffitt, T., Gregory, A., Goldman-Mellor, S., Nolan, P., Poulton, R., & Caspi, A. (2015). Social jetlag, obesity and metabolic disorder: Investigation in a cohort study. International Journal of Obesity, 39(5), 842-848.
  9. National Institute of General Medical Sciences. (2012). Circadian Rhythms Fact Sheet. Retrieved from
  10. National Sleep Foundation. (n.d.). Sleep and The Circadian System. Retrieved from