What you NEED to know about SLEEP Part 2: Sleep and Your Health

 What you NEED to know about SLEEP Part 2: Sleep and Your Health

What you NEED to know about SLEEP Part 2: Sleep and Your Health

This is the second instalment in a 3 part series on Sleep! Part 1 explores the vexing question of How Much Sleep Do I Need? This post will explore how much sleep we’re getting, and the impacts of short and long term sleep deprivation. In Part 3 I’ll share my bumper list of evidence-based tips to help you improve your sleep! Click here to subscribe to my newsletter to make sure Part 3 lands in your inbox!

Sleep is essential for good physical, mental and emotional health

Countless studies support the importance of sleep for activation and support of our body’s restorative processes, and its protective effect in relation to our immune system, brain and memory function, emotional regulation and much more. For more information on what happens to our body when we sleep, check out Part 1 in this series.

But we are not getting enough sleep!

Studies show that we are getting less sleep, and our rates of insomnia and sleep disorders has risen over the last few decades. It’s no exaggeration to state that sleep deprivation is at pandemic levels. You, me and everyone we know are sleep deprived to some degree.

In researching this important health topic I was surprised to discover that there is not a whole lot of data on exactly how much sleep Australians are getting. For example, sleep data was not collected during the Australian National Health Survey. So most of the Australian statistics we might read in the news come from a 2016 study by the Australian Sleep Health Foundation, which only surveyed 1,011 adults, or the Sealy Sleep Census, which included data from 5 countries, and surveyed only 2,300 Australians.

The Sleep Health Foundation Survey reported that almost half of those surveyed experienced deficits in sleep duration or quality, whilst the Sealy Survey reported that only 25% of Australians get 8 hours of sleep per night.

They are pretty sobering statistics, but when it comes to sleep and wellbeing, rather than focus on population studies, I think it’s most helpful to focus on ourselves. Are you getting enough hours of sleep per night? And are you waking refreshed and ready to go or are you exhausted and yawning your way through your day?

What can go wrong with our sleep?

Insomnia is the blanket term for the inability to initiate or maintain sleep. Someone is said to have chronic insomnia if they experience at least three nights of insomnia per week and for at least three months. But we don’t have to fit into the technical definition of insomnia to become sleep deprived.

There are a LOT of reasons why we might not be getting enough sleep, or enough quality sleep. Sleep scientists categorise sleep risk-factors into the following five categories:

1. Lifestyle factors including excessive caffeine, alcohol, drug abuse, shift work, and jet lag.

2. Environmental factors including excessive noise in your sleep environment, and excessive light.

3. Psychosocial factors including anxiety, worry, rumination, having babies and young children in your household or being a caregiver to a family member with a chronic or terminal illness.

4. Medical issues including pain, lung disease, kidney disease. neurodegenerative disease, mental illness or diabetes.

5. Diagnosed Sleep disorders. There are actually more than 100 different classifications of sleep disorders, but problems with our sleep can be broadly classified into one of the following five broad areas:

  • Sleep delay: where it can take us longer than 15-20 minutes to fall asleep.

  • Early awakening: where you wake up in the early hours of the morning and can’t get back to sleep;

  • Sleep Disruption or Fragmentation: where we have difficulty maintaining our sleep throughout the night; and

  • Disruptive events during sleep such as restless leg syndrome or sleep apnoea

  • Sleep Deprivation: where we just don’t get the hours and/or quality of sleep that our body needs (which can wholly or in part be due to the first three issues).

I will be unpicking a lot of these sleep-risk factors in Part 3 of this series, so make sure you subscribe to my newsletter to get my bumper list of evidence-based tips for better sleep delivered straight to your inbox!

The health impacts of lack of sleep

Acute and chronic lack of sleep can have adverse impacts on virtually all areas of our lives from our physiological health, to our cognitive and work performance, and even our mood and interpersonal relationships.

Did you know that insomnia and lack of sleep has been linked with a number of catastrophic disasters including the Exxon Valdez oil spill, the Space Shuttle Challenger explosion, the Chernobyl nuclear meltdown, and Three Mile Island? Does it make you wonder if these disasters have been avoided if those involved had made better sleep a priority?

Short-term effects of insufficient or inadequate sleep

Even one night of poor sleep can have an impact. Studies have shown the following effects of short-term sleep deficits:

  • Lowered alertness and daytime sleepiness

  • Impaired attention and cognition

  • Increased reaction time and impaired hand-eye co-ordination

  • Memory impairments

  • Work and athletic performance deficits

  • Heightened stress response

  • Increased perception of pain

  • Lowered mood and irritability, and increased emotional reactivity, which can increase the possibility of interpersonal conflict

  • Increased likelihood of car accidents

  • Impaired glucose tolerance and impaired insulin sensitivity

  • Disruption of appetite-regulating hormones leptin and ghrelin, driving an increase in apetite and overeating

  • Impaired immune response and alteration in inflammatory markers

The good news is that the short-term impacts of poor sleep can be pretty easily rectified, and are generally fully reversible, if we get our sleep back on track sooner rather than later.

It’s when our less-than-ideal sleep becomes a long-term, chronic pattern that things start to get a lot more serious…

Long-term effects of impaired sleep

The most concerning health impacts occur when our sleep deprivation becomes chronic.

Brain Health and Cognition

Sleep is essential for brain health and optimal cognitive function. Studies have demonstrated that short-term sleep disruption can result in lowered alertness, impaired attention, cognition, executive function and hand-eye co-ordination, and memory impairments. These effects tend to persist and amplify when sleep deprivation becomes chronic. Studies report impairments to executive functions that affect memory, concentration, planning, organisation and, most worryingly, our judgment.

More disturbingly, epidemiological studies have show a link between chronic sleep deprivation and dementia risk. This makes sense, as scientists have recently discovered that our brain “cleans house” during sleep, particularly deep, slow-wave sleep. There is now an emerging body of studies seeking to explore the link between chronic sleep deprivation and the plaques and other toxins that are observed in the brains of people with Alzheimer’s disease.

Mood, mental health and social wellbeing

It is well established that chronic sleep deprivation can severely impact our mood as well as how we process our emotions, judge and assess situations and people around us. Our ability to empathise with others may lower. People who are chronically sleep deprived feel lonelier and less motivated to socialise, which in turn can make them less socially attractive to others. This can have a pretty significant adverse impact on our interpersonal relationships and our work performance, especially if our work involves high levels of interpersonal interactions and/or requires empathy.

More worryingly, chronic sleep deprivation is strongly associated with mental illness, and in particular depression. In fact, sleep deprivation has been identified as a major causal factor in the development of depression. This is why psychologists and psychiatrists recommend addressing sleep as one of the recommended “lifestyle interventions” for people with depression.

And of course this bleeds into the rest of our work and personal life. Lack of sleep can make us irritable, impatient, more emotionally reactive and impair our cognition and attention, so it is hardly surprising that studies find that it impacts our relationships and work performance.

Glycemic Response, Insulin resistance and Type 2 Diabetes

Those with poor sleep are at significantly higher risk of type 2 diabetes. It is well established that sleep deprivation reduces glucose tolerance and insulin sensitivity at both the cellular and whole-body level. Insulin resistance is a major risk factor, and widely regarded as a pathophysiological precursor for Type 2 diabetes (unless lifestyle changes or medical intervention brings it under control).

Metabolism, appetite and weight gain

Numerous studies support the importance of regular sleep for normal metabolic functioning. Sleep deprivation is now a known risk-factor for weight gan and obesity. Epidemiological (population) studies have long shown a link between sleep deprivation and BMI (body mass index). Physiological and experimental studies have uncovered a number of inter-related mechanisms which link sleep deprivation and weight gain:

  • Insulin resistance: as described above, sleep deprivation impairs our insulin sensitivity which over time can lead to insulin resistance. The high levels of circulating insulin we see in people with insulin resistance push our bodies towards fat storage and can undermine our fat-burning efforts.

  • Appetite, Food/Calorie Consumption and Food Choices: Sleep deprivation impacts the hormones which regulate our appetite. Ghrelin, which stimulates hunger, increases whilst leptin, which signals satiety, decreases. This may explain in part why insufficient sleep is known to increase appetite and food/calorie consumption, and even impact the kinds of foods we crave, driving us to seek out foods that are high in both carbs/sugar and fat. There is also some evidence that sleep deprivation alters the reward centre of our brains, impacting our food-seeking behaviour. And it has also been suggested that shorter sleep time = more time awake and therefore more opportunity to eat!

  • Reduced physical activity: sleep deprivation leads to daytime sleepiness and fatigue, which then flows on to reduced motivation to exercise and increased sedentary behaviour.

  • Increased fat mass and reduced lean muscle mass: Our body composition has a significant impact on our metabolic rate. In addition to increased fat accumulation via the mechanisms described above, sleep deprivation can also undermine our body’s processes that maintain and build lean muscle tissue, and reduce the amount of energy our body burns.

Endocrine and hormonal imbalances

Our appetite-regulating hormones aren’t the only ones that can go haywire when we’re sleep deprived. Sleep deprivation upregulates the activity of our sympathetic nervous system. Studies also show increases in cortisol (a hormone associated with chronic stress), lowered melatonin and growth hormone secretion, and impaired thyroid function.

Cardiovascular health

The longer your sleep deprivation persists, the greater your risk of hypertension and endothelial dysfunction. Studies have also shown that our blood pressure doesn’t drop as far during sleep when we are chronically sleep deprived, and also that our morning surge in BP is increased.

But the risks to our cardiovascular health don’t stop at hypertension. Epidemiological studies consistently find links between chronic sleep deprivation and risk of atherosclerosis and even heart attack. People who consistently sleep less than 5 hours per night have been found to have 2-3 times the heart attack risk of people who sleep 7 hours a night, and higher risk of stroke. Studies investigating the physiological impacts of impaired sleep indicate that this is likely due to combined inputs of impaired glucose metabolism, increased inflammation (strongly associated with CVD risk) and impacts on our sympathetic nervous system. Studies show that C-Reactive Protein, a known marker for CVD risk, will elevate after only a week of impaired sleep.

Immune function and inflammation

Sleep deprivation has been sown to impair our immune function, increasing our risk of infection and even cancer. It is associated with impaired T cell proliferation, reduction in decreases in natural killer (NK) cell activity, and up regulation of certain pro inflammatory processes. Experimental studies where people voluntarily undergo sleep restriction have shown that insufficient sleep will raise our body’s inflammatory markers, including C-Reactive Protein and IL-6. Chronic inflammation is pathophysiologically linked to cardiovascular disease, obesity, type 2 diabetes and even mental health and mood disorders.

Cancer risk

An increasing number of studies are highlighting the link between sleep deprivation (and disruption of our circadian rhythm) and our risk of certain types of cancer, including colorectal and breast cancer. The mechanisms are still being investigated, but at this stage a lot of attention is being focussed on night-time light exposure. Exposure to light at night decreases production of melatonin, which can lead to hormonal imbalances. Melatonin also plays a role in DNA repair, tumour inhibition, and free-radical scavenging.

Mortality risk

So we know that over time, chronic sleep deprivation will erode our physical and emotional/mental wellbeing, and push us onto the road to long-term chronic disease. But we also need to know that sleep deprivation can drastically shorten our lives. It has been linked with seven of the fifteen leading causes of death in the United States, including cardiovascular disease, diabetes, septicaemia, hypertension, and accidents.

Sleep derivation has been identified as a factor in traffic and industrial accidents, as well as a number of headline-making disasters such as Chernobyl and the Exxon Valdez oil spill. In fact, driver sleep deprivation has been described as being as dangerous as being over the blood-alcohol limit. And chronic sleep deprivation is associated not only with depression but also with suicidal ideation (thoughts) and attempts.

Your appearance

For most of us this would seem logical, but some wonderful scientists very helpfully went ahead and measured this anyway. Chronic sleep interferes with our body’s restorative processes, and is associated with increased cortisol levels. Cortisol is known to break down collagen, so this might explain why chronic sleep deprivation is associated with dark circles and premature wrinkling. So if nothing else motivates you to improve your sleep habits, maybe a a bit of old fashioned vanity or a desire to turn back the clock might do it??

That’s a pretty frightening list, isn’t it?

Sleep deprivation impacts almost every facet of physical, mental and emotional health. But my intention wasn’t to frighten you, but to impress upon you (and, quite honestly, myself!!) that, even though it is so easy to stay up an extra hour or two, we all need to put sleep right up at the top of our health-and wellbeing list!

But there is a silver lining to this very dark cloud!

A small but growing body of research indicates that there is significant scope to halt and even reverse a lot of the above harmful health impacts by simply committing to (and actually getting!) 7-8 consistent hours of sleep over the long term! And benefits can be seen in as little as 2-4 weeks.

So are you ready to join me in taking a few simple steps to improve your sleep?

Great! Next week I will be posting my number list of evidence-based tips to help you improve your sleep, one small, simple, absolutely-do-able tweak at a time! Subscribe to my newsletter HERE to make sure it lands in your inbox!


Adams RJ, Appleton SL, Taylor AW, Gill TK, Lang C, McEvoy RD, Antic NA. Sleep health of Australian adults in 2016: results of the 2016 Sleep Health Foundation national survey. Sleep health. 2017 Feb 1;3(1):35-42.

Medic G, Wille M, Hemels ME. Short-and long-term health consequences of sleep disruption. Nature and science of sleep. 2017;9:151.

Itani O, Jike M, Watanabe N, Kaneita Y. Short sleep duration and health outcomes: a systematic review, meta-analysis, and meta-regression. Sleep Med. (2017) 32:246–56.

Krause AJ, Simon EB, Mander BA, Greer SM, Saletin JM, Goldstein-Piekarski AN, Walker MP. The sleep-deprived human brain. Nature Reviews Neuroscience. 2017 Jul;18(7):404.

Liang Y, Qu LB, Liu H. Non-linear associations between sleep duration and the risks of mild cognitive impairment/dementia and cognitive decline: a dose–response meta-analysis of observational studies. Aging clinical and experimental research. 2018 Jul 23:1-2.

Killgore WD. Effects of sleep deprivation on cognition. Progress in brain research 2010, 185:05-129.

Meerlo P, Sgoifo A, Suchecki D. Restricted and disrupted sleep: effects on autonomic function, neuroendocrine stress systems and stress responsivity. Sleep Med Rev. 2008;12(3):197–210.

Guadagni V, Burles F, Valera S, Hardwicke-Brown E, Ferrara M, Campbell T, Iaria G. The relationship between quality of sleep and emotional empathy. Journal of psychophysiology. 2016 Sep 13.

Meerlo P, Havekes R, Steiger A. Chronically restricted or disrupted sleep as a causal factor in the development of depression. Curr Top Behav Neurosci. 2015;25:459–481.

Ong AD, Kim S, Young S, Steptoe A. Positive affect and sleep: A systematic review. Sleep medicine reviews. 2017 Oct 1;35:21-32.

Finan PH, Quartana PJ, Smith MT. The effects of sleep continuity disruption on positive mood and sleep architecture in healthy adults. Sleep. 2015;38(11):1735–1742.

McCoy JG, Strecker RE. The cognitive cost of sleep lost. Neurobiol Learn Mem. 2011;96(4):564–582.

Tempesta D, De GL, Natale V, Ferrara M. Emotional memory processing is influenced by sleep quality. Sleep Med. 2015;16(7):862–870.

Eti Ben Simon, Matthew P. Walker. Sleep loss causes social withdrawal and loneliness. Nature Communications, 2018; 9 (1)

Knutson KL, Van CE, Rathouz PJ, et al. Association between sleep and blood pressure in midlife: the CARDIA sleep study. Arch Intern Med. 2009;169(11):1055–1061.

Phillips B, Mannino DM. Do insomnia complaints cause hypertension or cardiovascular disease? J Clin Sleep Med. 2007;3(5):489–494.

St-Onge MP, Grandner MA, Brown D, Conroy MB, Jean-Louis G, Coons M, Bhatt DL. Sleep Duration and Quality: Impact on Lifestyle Behaviors and Cardiometabolic Health: A Scientific Statement From the American Heart Association. Circulation 2016; 134: e367-e386

Grandner MA, Alfonso-Miller P, Fernandez-Mendoza J, Shetty S, Shenoy S, Combs D. Sleep: important considerations for the prevention of cardiovascular disease. Curr Opin Cardiol 2016; 31: 551-565

Palagini L, Maria Bruno R, Gemignani A, Baglioni C, Ghiadoni L, Riemann D. Sleep loss and hypertension: a systematic review. Current pharmaceutical design. 2013 Apr 1;19(13):2409-19.

Meisinger C, Heier M, Lowel H, Schneider A, Doring A. Sleep duration and sleep complaints and risk of myocardial infarction in middle-aged men and women from the general population: the MONICA/KORA Augsburg cohort study. Sleep. 2007;30(9):1121–1127.

Dolezal BA, Neufeld EV, Boland DM, et al (2017). Interrelationship between Sleep and Exercise: A Systematic Review. Advances in Preventive Medicine, vol. 2017, 1364387.

Cedernaes J, Schioth HB, Benedict C. Determinants of shortened, disrupted, and mistimed sleep and associated metabolic health consequences in healthy humans. Diabetes. 2015;64(4):1073–1080.

Lauderdale DS, Knutson KL, Rathouz PJ, Yan LL, Hulley SB, Liu K. Cross-sectional and longitudinal associations between objectively measured sleep duration and body mass index: the CARDIA Sleep Study. Am J Epidemiol. 2009;170(7):805–813.

Wu, Y.; Zhai, L.; Zhang, D. Sleep duration and obesity among adults: A meta-analysis of prospective studies. Sleep Med. 2014, 15, 1456–1462.

Maugeri A, Medina-Inojosa J, Kunzova S, Agodi A, Barchitta M, Sochor O, Lopez-Jimenez F, Geda Y, Vinciguerra M. Sleep Duration and Excessive Daytime Sleepiness Are Associated with Obesity Independent of Diet and Physical Activity. Nutrients. 2018 Sep 3;10(9):1219.

Chaput JP. Sleep patterns, diet quality and energy balance. Physiology & behavior. 2014 Jul 31;134:86-91.

Dashti HS, Scheer FA, Jacques PF, Lamon-Fava S, Ordovás JM. Short sleep duration and dietary intake: epidemiologic evidence, mechanisms, and health implications. Advances in nutrition. 2015 Nov 10;6(6):648-59.

Dolezal BA, Neufeld EV, Boland DM, et al (2017). Interrelationship between Sleep and Exercise: A Systematic Review. Advances in Preventive Medicine, vol. 2017, 1364387.

Stamatakis KA, Punjabi NM. Effects of sleep fragmentation on glucose metabolism in normal subjects. Chest. 2010;137(1):95–101.

Grandner MA, Seixas A, Shetty S, Shenoy S. Sleep duration and diabetes risk: population trends and potential mechanisms. Current diabetes reports. 2016 Nov 1;16(11):106.

Cappuccio FP, D’Elia L, Strazzullo P, Miller MA. Quantity and quality of sleep and incidence of type 2 diabetes: a systematic review and meta-analysis. Diabetes Care. 2010;33(2):414–420.

van Leeuwen WM, Lehto M, Karisola P, Lindholm H, Luukkonen R, Sallinen M, et al. Sleep restriction increases the risk of developing cardiovascular diseases by augmenting proinflammatory responses through IL-17 and CRP. PLoS ONE (2009) 4:e4589.

Thompson CL, Larkin EK, Patel S, Berger NA, Redline S, Li L. Short duration of sleep increases risk of colorectal adenoma. Cancer. 2011;117(4):841–847.

Fang HF, Miao NF, Chen CD, Sithole T, Chung MH. Risk of cancer in patients with insomnia, parasomnia, and obstructive sleep apnea: a Nationwide Nested Case-Control Study. J Cancer. 2015;6(11):1140–1147.

Prather AA, Janicki-Deverts D, Hall MH, Cohen S. Behaviorally assessed sleep and susceptibility to the common cold. Sleep. 2015 Sep 1;38(9):1353-9.

Carroll JE, Irwin MR, Levine M, Seeman TE, Absher D, Assimes T, Horvath S. Epigenetic aging and immune senescence in women with insomnia symptoms: findings from the Women’s Health Initiative Study. Biological psychiatry. 2017 Jan 15;81(2):136-44.

Prather AA, Leung CW. Association of insufficient sleep with respiratory infection among adults in the United States. JAMA internal medicine. 2016 Jun 1;176(6):850-2.

Kim TW, Jeong JH, Hong SC. The impact of sleep and circadian disturbance on hormones and metabolism. International journal of endocrinology. 2015;2015.

Shen X, Wu Y, Zhang D. Nighttime sleep duration, 24-hour sleep duration and risk of all-cause mortality among adults: a meta-analysis of prospective cohort studies. Scientific reports. 2016 Feb 22;6:21480.

Hoevenaar-Blom MP, Spijkerman AM, Kromhout D, Verschuren WM. Sufficient sleep duration contributes to lower cardiovascular disease risk in addition to four traditional lifestyle factors: the MORGEN study. Eur J Prev Cardiol 2014; 21: 1367-1375

Al Khatib HK, Hall WL, Creedon A, Ooi E, Masri T, McGowan L, Harding SV, Darzi J, Pot GK. Sleep extension is a feasible lifestyle intervention in free-living adults who are habitually short sleepers: a potential strategy for decreasing intake of free sugars? A randomized controlled pilot study. The American journal of clinical nutrition. 2018 Jan 1;107(1):43-53.

Pizinger TM, Aggarwal B, St-Onge MP. Sleep Extension in Short Sleepers: An Evaluation of Feasibility and Effectiveness for Weight Management and Cardiometabolic Disease Prevention. Frontiers in endocrinology. 2018;9.

Haack M, Serrador J, Cohen D, Simpson N, Meier-Ewert H, Mullington JM. Increasing sleep duration to lower beat-to-beat blood pressure: a pilot study. J Sleep Res. (2013) 22:295–304.

McGrath ER, Espie CA, Power AM, Newell AW, Kelly J, Duffy C, et al. . Sleep to lower elevated blood pressure: a randomized controlled trial (SLEPT). Am J Hypertens. (2017) 30:319–27.

Leproult R, Deliens G, Gilson M, Peigneux P. Beneficial impact of sleep extension on fasting insulin sensitivity in adults with habitual sleep restriction. Sleep 38:707–15.

Faraut B, Boudjeltia KZ, Dyzma M, Rousseau A, David E, Stenuit P, et al. . Benefits of napping and an extended duration of recovery sleep on alertness and immune cells after acute sleep restriction. Brain Behav Immun. (2011) 25:16–24.

Pejovic S, Basta M, Vgontzas AN, Kritikou I, Shaffer ML, Tsaoussoglou M, et al. . Effects of recovery sleep after one work week of mild sleep restriction on interleukin-6 and cortisol secretion and daytime sleepiness and performance. Am J Physiol Endocrinol Metab. (2013) 305:E890–6.