By Susannah Reid,

It is common knowledge that we need to sleep well to stay healthy and have the ability to focus and perform well each day. Napping is both a daily routine and a strategy to make up a few hours of sleep. Over the last 30 years’ chronic sleep deprivation has gradually increased (1). Studies have seen a link between prediabetes, poor body composition and chronic lack of sleep (1). From this trend toward less sleep, a link between irregular sleep patterns and metabolic dysfunction has emerged. Metabolic syndrome has recently been linked to naps that are longer than 40 minutes (5). Feeling extremely tiring and having an urge to take naps during the day may also indicate ill metabolic health (4).

Daytime naps, if your schedule permits such luxuries, are commonly thought to be health promoting and have been shown to reduce disease risk (2). In fact, short power naps lasting under 30 minutes are related to lower cardiovascular disease risk (5). Naska et al., studied Greek men and reported that coronary heart disease risk was reduced in those who took an afternoon siesta (2). The heart health promoting effect of napping appeared strongest with regular daytime naps and working age men benefited most from napping. Other studies have found similar results in other Mediterranean, Latin American countries, where napping is the cultural norm.

More recently, Japanese researchers looked into how metabolic disease risk and napping or feeling tired during the day are related. A meta-analysis examined data from 21 studies conducted in Western and Asian countries to look at the relationship between napping and metabolic health. Yamada et al., found that naps over 90 minutes long actually increased CVD risk by 50% (5). Shorter naps were not associated with this risk.

Results indicate that daytime naps over 1-hour are linked with higher risk of excess midline fat, poorly regulated blood pressure, blood glucose and high cholesterol (5). These metabolic dysfunctions comprise what is known as metabolic syndrome. When considering metabolic syndrome, it is important to note that disordered breathing has been found to be a manifestation of metabolic syndrome (3). Those with difficulty breathing while lying down and sleeping, wake up frequently during the night resulting in poor sleep quality that can lead to chronic sleep deprivation and daytime sleepiness. Punjabi et al., identified a link between disrupted sleep due to irregular breathing and signs of prediabetes and metabolic syndrome (3). This makes sense considering that even short term sleep deprivation results in altered glucose metabolism, increased appetite and reduced energy output (1).

Napping during the day has also be linked with increased sleeplessness during the night (3). This seems to occur due to increased sympathetic activation following sleep loss and increased cortisol output in the evening following sleep loss (4). In terms of metabolic health, it appears that a vicious cycle forms between sleeping poorly, eating a bit more than usual to get more energy, being less active, taking a nap and again getting inadequate sleep at night. Short term sleep loss has been seen to increase cortisol production and elevate blood levels in interleukin-6, an inflammatory marker (4). This finding suggests that many of the metabolic effects associated with daytime napping appear after chronic sleep deprivation, rather than several nights of sleep loss. Short term deprivation, does however produce a metabolically stressed environment in the body.

Sleeping and napping habits may be an indicator of future health and disease risk. When it comes to metabolic health, the purpose for the nap also appears to be a determining factor. If napping is triggered by chronic sleep loss or feeling sleepy then, it seems that metabolic risks are larger. The health promoting effect of naps in countries where daytime siesta is part of the day could be due to the naps being short and part of the daily routine.

Sleep routines are often overlooked in today’s culture. Ensuring quality sleep each night may be the missing piece that could make a good exercise and a diet routine even more effective. On the other side of this, frequent napping and daytime sleepiness could be an important warning sign that should be heeded in order to restore health and life balance. If your sleep quality has been poor for sometime, it may be worth looking deeper into your metabolic health and getting some blood work done.

 

References:

  1. Knutson, K. L., Spiegel, K., Penev, P., & Van Cauter, E. (2007). The metabolic consequences of sleep deprivation. Sleep medicine reviews,11(3), 163-178.
  2. Naska, A., Oikonomou, E., Trichopoulou, A., Psaltopoulou, T., & Trichopoulos, D. (2007). Siesta in healthy adults and coronary mortality in the general population. Archives of internal medicine, 167(3), 296-301.
  3. Punjabi, N. M., Shahar, E., Redline, S., Gottlieb, D. J., Givelber, R., Resnick, H. E., & Sleep Heart Health Study Investigators. (2004). Sleep-disordered breathing, glucose intolerance, and insulin resistance the sleep heart health study. American journal of epidemiology, 160(6), 521-530.
  4. Vgontzas, A. N., Pejovic, S., Zoumakis, E., Lin, H. M., Bixler, E. O., Basta, M., … & Chrousos, G. P. (2007). Daytime napping after a night of sleep loss decreases sleepiness, improves performance, and causes beneficial changes in cortisol and interleukin-6 secretion. American Journal of Physiology-Endocrinology and Metabolism, 292(1), E253-E261.
  5. Yamada, T., Nobuhiro, S., & Takashi, K. (2016). DAYTIME NAPPING, DAYTIME SLEEPINESS AND THE RISK OF METABOLIC DISEASES: DOSE-RESPONSE META-ANALYSIS USING RESTRICTED CUBIC SPLINE MODEL. Journal of the American College of Cardiology, 67(13_S), 1951-1951.