How to Improve Your Sleep

The effects of sleep on health and the effects of aspects of health (like nutrition, mindfulness, and exercise) on sleep are clear. A large body of research shows that this relationship is bi-directional and also that there are many things we can do to improve our sleep and by extension our health.

The reality is that most of these interventions are also what we do simply to improve our health and performance. As I often say, if you take care of the big things in health…and the little things tend to fall into line!

There are some specific things we can do for our ‘sleep hygiene’ which can also provide the ‘icing on the cake’ that tips our balance from poorer, to better sleep.

Eat mostly unrefined foods

Diets that focus on a mostly unrefined selection of foods like the Mediterranean Diet, tend to promote longer and better-quality sleep,^1-3 and this is especially true when they include more fruits and vegetables. Conversely, diets higher in sugar, sweets, and snacks are associated with reduced sleep quality.⁴ Ultra-refined foods are also associated with obesity and this is known to also affect sleep.^{4, 5} Eating more unrefined foods, and especially foods like veggies, berries, and fruit (if you tolerate carbohydrates well) also help to supply vitamin C and flavonoids associated with better sleep.⁶

Eat 2-4 meals per day. Don’t snack!

Missing main meals and snacking is associated with worsened diet quality and poorer sleep.^{4, 7}  So, instead, we should focus on eating good, healthy meals, until we are full, and then eat again (a healthy, well-balanced meal) when we are hungry, rather than snacking.

Eat plenty of protein and veggies

Vegetables are associated with improved sleep,^{6, 8, 9} as are adequate protein intakes.⁸ You don’t need to go overboard with this as very high protein intakes don’t necessarily improve sleep further.¹⁰

Eat 2-3+ fist-sized serves of vegetables at each meal and 1-2 palm-sized serves of a protein food

Get out in the sun for at least 10 min per day (but don’t burn!)

Vitamin D helps to regulate the sleep-wake cycle,^{11, 12} and sun exposure also helps to regulate our natural circadian (day-night) patterns.¹² So, getting out into the sun helps provide a one-two punch for improving sleep.

If we can’t get out in the sun all the time, or during winter when vitamin D production from sun exposure is lower, taking a vitamin D supplement can also help to preserve vitamin D level and improve sleep duration and quality.^{13, 14}

Get out in the sun with face, arms, and legs (or more!) exposed for 10 min per day, and/or take a vitamin D supplement (600 – 4000 iu per day)

Consider zinc and magnesium before bed

Magnesium helps reduce excessive nerve firing and is considered our primary ‘relaxing’ mineral¹⁵ which can improve sleep.¹⁶ Magnesium is likely to both improve sleep and reduce drowsiness, while poor levels of magnesium worse sleep.^17-20 It can also reduce some of the negative effects on performance from not getting enough sleep.²¹Magnesium supplementation has been shown to benefit sleep.²²

Similarly, zinc is involved in many hundreds of enzymatic reactions in the body, some of which are critical to sleep-cycles. Zinc supplementation and higher intakes of zinc-rich foods improve the amount and quality of sleep,^23-25

If you’re having trouble sleeping, consider a zinc/magnesium supplement containing ~400 mg magnesium and 15 mg zinc.

Note: A great way to get sufficient zinc and magnesium is within a quality multi-vitamin that also includes ~900 mcg of copper (which is important to have ‘in balance’ with zinc)

Meditate before bed

Mindfulness and meditation target key risk factors of poor sleep, such as awareness, control, and most importantly acceptance (especially of the things you can’t control!)²⁶

Meditative practices such as ‘mindfulness-based stress reduction’ (a meditation practice based originally drawn from Eastern traditions like Buddhism and now used as a medical intervention) is likely to improve sleep quality as much or more as other active interventions, and more than passive ‘control’ actions.^27-29 Similarly, mindful movement practices like meditation, yoga, chi gong, and Pilates have been shown to have beneficial effects on sleep quality, along with improvements in quality of life, physical performance, and depression,^{30, 31} and might help to reduce chronic pain and improve sleep quality in people with chronic illness.³²

Use mindfulness of breath meditation before bed (or take up another mindfulness practice like yoga or qi gong)

Get more (and earlier) sleep

There is a clear link between reduced sleep duration and poorer health. For example, in a study comparing sleep extension with napping, improved sleep hygiene, and post-exercise recovery strategies in athletes (18-24 yrs.) it was found that longer sleep had the greatest effect on subsequent performance. ³³

Interestingly, while we often hear advice that ‘banking’ sleep is ineffective (getting more sleep before or after a period of reduced sleep), a systematic review of sleep patterns of shift-workers has suggested that banking sleep before shift-work can help to improve safety, performance, and reduce fatigue.³⁴

Try going to bed ½ an hour or more earlier than usual and notice any differences to your waking and daily energy and mental performance

Consider cognitive behavioural practices

Pre-sleep practices drawn from cognitive behavioural therapy result in increased sleep times, reduced time-to-sleep, and improved sleep quality, resulting in additional improvements to daytime sleepiness, depression, and anxiety.^{31, 35, 36}

Have a warm bath or shower before bed

Taking a warm bath or shower increases body temperature and this results in greater peripheral blood flow and vasodilation to reduce body temperature to normal. This heating and cooling is thought to help elicit sleep and increase the release of sleep-inducing hormones like melatonin as it mimics one of the ‘sleep signals’ of our circadian rhythm – the inevitable cooling of the environment as the sun sets. A bath or shower of ~40-42.5 degrees Celsius has been shown to improve sleep quality and time-to-sleep when taken around 1-2 hours before bed.³⁷

If you’re having trouble sleeping, try having a warm bath or shower before bed

Exercise

Exercise improves sleep quality, duration and time-to-sleep.^38-41 In particular, exercise is effective for helping to combat insomnia.^{41, 42} Exercising in the evening also helps rather than hinders sleep duration and quality overall, however, vigorous exercise less than an hour before bed can reduce sleep duration, increase the time it takes to get to sleep and reduce sleep quality.⁴³ In a more recent review (from 2017) of intervention studies, 29 of 34 studies concluded that exercise improved either sleep duration of quality,⁴⁴ and in a meta-analysis of the same year a significant improvement in sleep was seen with exercise.³⁸ In those with sleep disturbance, there is an association with obesity (which is improved by exercise) and improvements to the severity of sleep disturbances and quality of life resulting from exercise.⁴⁵

Resistance exercise

Most of the recent reviews have focussed on aerobic or mindful exercise regimens. In a recent review of the effects of resistance (weight) training, chronic resistance exercise was found to improve all aspects of sleep, with the greatest benefit for sleep quality and the suggestion that resistance exercise also improves anxiety and depression.⁴⁶

Get into a habit of regular exercise (check out our health kick-start course) but be aware of exercising intensely too close to bed-time

Reduce use of screen devices and exposure to media…

There is a strong and consistent association between bedtime use of screen devices like phones and tablets with inadequate sleep, poor sleep quality and excessive daytime sleepiness. ⁴⁷ There is a greater than two-fold increased risk of having sleep problems if you compulsively use the internet (‘internet addiction’).⁴⁸

Turn off your phone around 2 hours or more before your bedtime. Limit excessive light exposure at night, reduce the use of screen devices wherever possible after dark, and use blue-light blocking glasses or apps

Light therapy

Human circadian rhythms are influenced heavily by light and dark cycles. When it is lighter, we wake up and when it is darker, we tend towards sleep. Thus, bright light therapy has been considered a way to help influence circadian rhythms and encourage better sleep. Meta-analysis has shown that bright light exposure (only earlier in the day!) can improve sleep duration, sleeping problems in general, reduce insomnia and reduce Alzheimer’s related sleep-problems.⁴⁹

Get out in natural sunlight in the morning and mid-day

Reduce caffeine

Caffeinated beverages have health benefits and can help to improve cognition and reduce the risk of neurodegenerative disorders,^50-52 but excessive use or use late in the day can reduce sleep quality and duration. Caffeine can reduce the time it takes to get to sleep and sleep quality. Additionally, slow-wave sleep crucial to the recovery and repair of the body is reduced, while sleep arousal is increased. Several factors influence the effect of caffeine on sleep; timing of intake and dosage are most important, while older adults may be more sensitive to these effects than younger people. There is also significant genetic variation in tolerance to caffeine.⁵³

Restrict caffeine to the morning and if you’re having trouble sleeping, reduce your intake of coffee, tea, and/or cocoa

Limit alcohol

Higher intakes of alcohol consumption increase the risk of sleep apnoea and reduce the quality of sleep.⁵⁴

Stick to the best health guidelines for alcohol (less than 5 drinks per week) and avoid drinking more than 3 drinks on any given day

Reduce noise

Noise (such as road or aircraft noise) can affect sleep quality.⁵⁵

Aromatherapy

Use of relaxing aromatherapy oils might help to improve sleep quality.⁵⁶

Look into deeper reasons for sleep disturbances

Inflicted trauma, including sexual violence and abuse, physical violence, or psychological aggression is known to increase sleep disturbance.⁵⁷ Interventions (some of which have been above) such as improved ‘sleep hygiene’, cognitive behavioural therapy, mindfulness and relaxation practices, and psychotherapy and hypnotherapy, can help us to deal with trauma and improve sleep.⁵⁸ Cognitive behavioural therapy shows particularly strong effects for improving sleep,⁵⁸ although these effects seem to be mostly related to subjective (self-reported) rather than laboratory measures of sleep.⁵⁹

Socioeconomics and sleep

Socioeconomic status is also known to affect sleep quality and in turn, lower sleep quality can reduce cognition and mental and physical performance and thus, reduce socioeconomic status (this is another good example of bidirectionality). A 2018 systematic review in the journal Psychiatry and Mental Health Studies of the impact of socioeconomic status on sleep suggested the following points⁶⁰:

• Socioeconomic status affects the development of sleep disorders in low-income populations, independently of gender, age, education, and country
• Sleep disorders may be indicators of high levels of stress
• Circadian rhythms and circadian cycle are affected by socioeconomic status
• Socioeconomic status and circadian disruption are associated with metabolic diseases such as diabetes and cancer
• The most widely correlated measures of socioeconomic status related to sleep disorders are social class, discrimination, ethnicity, low-income, occupation, education, obesity, neurodevelopmental and motor disabilities
• The most well-studied sleep disorders in association with socioeconomic status are insomnia, sleepiness, circadian rhythms sleep disorders, obstructive sleep apnoea and sleep disorders induced by substances like caffeine, opioids, nicotine, and alcohol

Consider seeing a licensed professional who can help you deal with any psychological traumas or challenges that are manifesting into poor sleep

Conclusion

Sleep has a large and bi-direction effect on health, meaning that the worse you sleep, the worse your health and vice versa! To improve our health and performance, improving sleep should be a priority, and to improve sleep we need to create ‘sleep rituals’. These sleep rituals are often called ‘sleep hygiene practices’ have been shown to improve sleep quality and duration.⁵⁸ Most importantly we should:

• Get to bed at a time that allows at least 7 hours of total sleep before waking
• This time should be extended if you are being woken by an alarm every morning or if you are waking excessively tired
• Sleep quality should be improved by reducing alcohol to safe levels (i.e. <5 drinks per week) and by eliminating caffeine in the afternoon and them moderating intake to your tolerance level
• Screen use should be limited in the evening, if possible, avoided within 2 hours of going to bed, and used with ‘blue light blocking’ apps, screens, or glasses after sunset
• Social media use should be limited, especially in the evening, to reduce stress
• Daily exercise should be undertaken per your recovery ability. Build your volume and intensity incrementally so that it does not become an excessive stressor that inhibits sleep
• Meditation, mindfulness, a hot shower, and/or some relaxing oils (not ingested), and a cup of relaxing herbal tea can be used to help induce sleep
• If past trauma is a reason for poor sleep, consider seeing a counsellor, psychotherapist, psychiatrist, or psychologist experienced in trauma counselling

References

1.         Campanini MZ, Guallar-Castillón P, Rodríguez-Artalejo F, Lopez-Garcia E. Mediterranean Diet and Changes in Sleep Duration and Indicators of Sleep Quality in Older Adults. Sleep. 2016;40(3).

2.         Godos J, Ferri R, Caraci F, Cosentino FII, Castellano S, Galvano F, et al. Adherence to the Mediterranean Diet is Associated with Better Sleep Quality in Italian Adults. Nutrients. 2019;11(5):976.

3.         Mamalaki E, Anastasiou CA, Ntanasi E, Tsapanou A, Kosmidis MH, Dardiotis E, et al. Associations between the mediterranean diet and sleep in older adults: Results from the hellenic longitudinal investigation of aging and diet study. Geriatrics & Gerontology International. 2018;18(11):1543-8.

4.         Ferranti R, Marventano S, Castellano S, Giogianni G, Nolfo F, Rametta S, et al. Sleep quality and duration is related with diet and obesity in young adolescent living in Sicily, Southern Italy. Sleep Science. 2016;9(2):117-22.

5.         Pagliai G, Dinu M, Casini A, Sofi F. Relationship between sleep pattern and efficacy of calorie-restricted Mediterranean diet in overweight/obese subjects. International journal of food sciences and nutrition. 2018;69(1):93-9.

6.         Noorwali EA, Cade JE, Burley VJ, Hardie LJ. The relationship between sleep duration and fruit/vegetable intakes in UK adults: a cross-sectional study from the National Diet and Nutrition Survey. BMJ open. 2018;8(4):e020810.

7.         Letellier LR. Sleep duration and its association with diet quality and weight status: The Ohio State University; 2019.

8.         St-Onge M-P, Mikic A, Pietrolungo CE. Effects of Diet on Sleep Quality. Advances in Nutrition. 2016;7(5):938-49.

9.         Zuraikat FM, St-Onge M-P. Chapter 22 – The Influence of Diet on Sleep. In: Watson RR, Preedy VR, editors. Neurological Modulation of Sleep: Academic Press; 2020. p. 205-15.

10.       Burgess V, Carson C, Ellerbroek A, Axelrod C, Peacock C, Silver TA, et al. High-Protein Diet has no Effect on Sleep Quality and Quantity in Exercise-Trained Men and Women. Journal of Exercise and Nutrition. 2019;2(1):1.

11.       Muscogiuri G, Barrea L, Scannapieco M, Di Somma C, Scacchi M, Aimaretti G, et al. The lullaby of the sun: the role of vitamin D in sleep disturbance. Sleep Medicine. 2019;54:262-5.

12.       Metlaine A. Chapter 25 – Sleep, Stress, and Vitamin D. In: Watson RR, Preedy VR, editors. Neurological Modulation of Sleep: Academic Press; 2020. p. 235-42.

13.       Mohammad Shahi M, Hosseini SA, Helli B, Haghighyzade MH, Abolfathi M. The effect of vitamin D supplement on quality of sleep in adult people with sleep disorders. Tehran University Medical Journal. 2017;75(6):443-8.

14.       Gao Q, Kou T, Zhuang B, Ren Y, Dong X, Wang Q. The Association between Vitamin D Deficiency and Sleep Disorders: A Systematic Review and Meta-Analysis. Nutrients. 2018;10(10):1395.

15.       Murck H, Holsboer F, Steiger A. Magnesium sulphate has GABA-Agonistic effects on sleep in healthy men. Biological Psychiatry. 1996;39(7):591.

16.       Murck H, Held K, Auer DP, Steiger A. Therapeutic sleep deprivation and magnesium: Modulators of the GABA/glutamate equilibrium. Pharmacopsychiatry. 2003;36(05):201.

17.       Nielsen FH. Chapter 31 – Relation between Magnesium Deficiency and Sleep Disorders and Associated Pathological Changes. In: Watson RR, editor. Modulation of Sleep by Obesity, Diabetes, Age, and Diet. San Diego: Academic Press; 2015. p. 291-6.

18.       Dralle D, Bödeker RH. Serum magnesium level and sleep behavior of newborn infants. European Journal of Pediatrics. 1980;134(3):239-43.

19.       Takase B, Akima T, Satomura K, Fumitaka, Ohsuzu, Mastui T, et al. Effects of chronic sleep deprivation on autonomic activity by examining heart rate variability, plasma catecholamine, and intracellular magnesium levels. Biomedicine & Pharmacotherapy. 2004;58:S35-S9.

20.       Cao Y, Zhen S, Taylor AW, Appleton S, Atlantis E, Shi Z. Magnesium Intake and Sleep Disorder Symptoms: Findings from the Jiangsu Nutrition Study of Chinese Adults at Five-Year Follow-Up. Nutrients. 2018;10(10):1354.

21.       Tanabe K, Yamamoto A, Suzuki N, Osada N, Yokoyama Y, Samejima H, et al. Efficacy of Oral Magnesium Administration on Decreased Exercise Tolerance in a State of Chronic Sleep Deprivation. JAPANESE CIRCULATION JOURNAL. 1998;62(5):341-6.

22.       Nielsen FH. Magnesium supplementation improves indicators of low magnesium status and inflammatory stress in adults older than 51 years with poor quality sleep. Magnesium Research. 2010;v. 23(no. 4):pp. 158-68-2010 v.23 no.4.

23.       Cherasse Y, Urade Y. Dietary Zinc Acts as a Sleep Modulator. International Journal of Molecular Sciences. 2017;18(11):2334.

24.       Saito H, Cherasse Y, Suzuki R, Mitarai M, Ueda F, Urade Y. Zinc-rich oysters as well as zinc-yeast- and astaxanthin-enriched food improved sleep efficiency and sleep onset in a randomized controlled trial of healthy individuals. Molecular Nutrition & Food Research. 2017;61(5):1600882.

25.       Gholipour Baradari A, Alipour A, Mahdavi A, Sharifi H, Nouraei SM, Emami Zeydi A. The Effect of Zinc Supplementation on Sleep Quality of ICU Nurses: A Double Blinded Randomized Controlled Trial. Workplace Health & Safety. 2018;66(4):191-200.

26.       Shallcross AJ, Visvanathan PD, Sperber SH, Duberstein ZT. Waking up to the problem of sleep: can mindfulness help? A review of theory and evidence for the effects of mindfulness for sleep. Current Opinion in Psychology. 2019;28:37-41.

27.       Winbush NY, Gross CR, Kreitzer MJ. The Effects of Mindfulness-Based Stress Reduction on Sleep Disturbance: A Systematic Review. EXPLORE. 2007;3(6):585-91.

28.       Rusch HL, Rosario M, Levison LM, Olivera A, Livingston WS, Wu T, et al. The effect of mindfulness meditation on sleep quality: a systematic review and meta-analysis of randomized controlled trials. Annals of the New York Academy of Sciences. 2019;1445(1):5-16.

29.       Wang Q, Zhang X, Wang Q, Zhang W. Interventional effect of mindfulness-based stress reduction on perceived stress and sleep disturbance in cancer patients: a systematic review. Chongqing Medicine. 2017;46(25):3547-50.

30.       Wang F, Eun-Kyoung Lee O, Feng F, Vitiello MV, Wang W, Benson H, et al. The effect of meditative movement on sleep quality: A systematic review. Sleep Medicine Reviews. 2016;30:43-52.

31.       Zeichner SB, Zeichner RL, Gogineni K, Shatil S, Ioachimescu O. Cognitive Behavioral Therapy for Insomnia, Mindfulness, and Yoga in Patients With Breast Cancer with Sleep Disturbance: A Literature Review. Breast Cancer: Basic and Clinical Research. 2017;11:1178223417745564.

32.       Zou L, Yeung A, Quan X, Boyden SD, Wang H. A Systematic Review and Meta-Analysis of Mindfulness-Based (Baduanjin) Exercise for Alleviating Musculoskeletal Pain and Improving Sleep Quality in People with Chronic Diseases. International Journal of Environmental Research and Public Health. 2018;15(2):206.

33.       Bonnar D, Bartel K, Kakoschke N, Lang C. Sleep Interventions Designed to Improve Athletic Performance and Recovery: A Systematic Review of Current Approaches. Sports Medicine. 2018;48(3):683-703.

34.       Patterson PD, Ghen JD, Antoon SF, Martin-Gill C, Guyette FX, Weiss PM, et al. Does evidence support “banking/extending sleep” by shift workers to mitigate fatigue, and/or to improve health, safety, or performance? A systematic review. Sleep Health. 2019;5(4):359-69.

35.       Blake MJ, Sheeber LB, Youssef GJ, Raniti MB, Allen NB. Systematic Review and Meta-analysis of Adolescent Cognitive–Behavioral Sleep Interventions. Clinical Child and Family Psychology Review. 2017;20(3):227-49.

36.       Murawski B, Wade L, Plotnikoff RC, Lubans DR, Duncan MJ. A systematic review and meta-analysis of cognitive and behavioral interventions to improve sleep health in adults without sleep disorders. Sleep Medicine Reviews. 2018;40:160-9.

37.       Haghayegh S, Khoshnevis S, Smolensky MH, Diller KR, Castriotta RJ. Before-bedtime passive body heating by warm shower or bath to improve sleep: A systematic review and meta-analysis. Sleep Med Rev. 2019;46:124-35.

38.       Kelley GA, Kelley KS. Exercise and sleep: a systematic review of previous meta-analyses. Journal of Evidence-Based Medicine. 2017;10(1):26-36.

39.       Dolezal BA, Neufeld EV, Boland DM, Martin JL, Cooper CB. Interrelationship between Sleep and Exercise: A Systematic Review. Advances in Preventive Medicine. 2017;2017:14.

40.       Lederman O, Ward PB, Firth J, Maloney C, Carney R, Vancampfort D, et al. Does exercise improve sleep quality in individuals with mental illness? A systematic review and meta-analysis. Journal of Psychiatric Research. 2019;109:96-106.

41.       Rubio-Arias JÁ, Marín-Cascales E, Ramos-Campo DJ, Hernandez AV, Pérez-López FR. Effect of exercise on sleep quality and insomnia in middle-aged women: A systematic review and meta-analysis of randomized controlled trials. Maturitas. 2017;100:49-56.

42.       Lowe H, Haddock G, Mulligan LD, Gregg L, Fuzellier-Hart A, Carter L-A, et al. Does exercise improve sleep for adults with insomnia? A systematic review with quality appraisal. Clinical Psychology Review. 2019;68:1-12.

43.       Stutz J, Eiholzer R, Spengler CM. Effects of Evening Exercise on Sleep in Healthy Participants: A Systematic Review and Meta-Analysis. Sports Medicine. 2019;49(2):269-87.

44.       Dolezal BA, Neufeld EV, Boland DM, Martin JL, Cooper CB. Interrelationship between Sleep and Exercise: A Systematic Review. Advances in Preventive Medicine. 2017;2017:1364387.

45.       Hargens TA, Kaleth AS, Edwards ES, Butner KL. Association between sleep disorders, obesity, and exercise: a review. Nat Sci Sleep. 2013;5:27-35.

46.       Kovacevic A, Mavros Y, Heisz JJ, Fiatarone Singh MA. The effect of resistance exercise on sleep: A systematic review of randomized controlled trials. Sleep Medicine Reviews. 2018;39:52-68.

47.       Carter B, Rees P, Hale L, Bhattacharjee D, Paradkar MS. Association Between Portable Screen-Based Media Device Access or Use and Sleep Outcomes: A Systematic Review and Meta-analysis. JAMA Pediatrics. 2016;170(12):1202-8.

48.       Alimoradi Z, Lin C-Y, Broström A, Bülow PH, Bajalan Z, Griffiths MD, et al. Internet addiction and sleep problems: A systematic review and meta-analysis. Sleep Medicine Reviews. 2019;47:51-61.

49.       van Maanen A, Meijer AM, van der Heijden KB, Oort FJ. The effects of light therapy on sleep problems: A systematic review and meta-analysis. Sleep Medicine Reviews. 2016;29:52-62.

50.       Irwin C, Khalesi S, Desbrow B, McCartney D. Effects of acute caffeine consumption following sleep loss on cognitive, physical, occupational and driving performance: A systematic review and meta-analysis. Neuroscience & Biobehavioral Reviews. 2020;108:877-88.

51.       Ruxton CHS. The impact of caffeine on mood, cognitive function, performance and hydration: a review of benefits and risks. Nutrition Bulletin. 2008;33(1):15-25.

52.       Panza F, Solfrizzi V, Barulli MR, Bonfiglio C, Guerra V, Osella A, et al. Coffee, tea, and caffeine consumption and prevention of late-life cognitive decline and dementia: A systematic review. The journal of nutrition, health & aging. 2015;19(3):313-28.

53.       Clark I, Landolt HP. Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials. Sleep Medicine Reviews. 2017;31:70-8.

54.       Simou E, Britton J, Leonardi-Bee J. Alcohol and the risk of sleep apnoea: a systematic review and meta-analysis. Sleep Medicine. 2018;42:38-46.

55.       Basner M, McGuire S. WHO Environmental Noise Guidelines for the European Region: A Systematic Review on Environmental Noise and Effects on Sleep. International Journal of Environmental Research and Public Health. 2018;15(3):519.

56.       Lin P-C, Lee P-H, Tseng S-J, Lin Y-M, Chen S-R, Hou W-H. Effects of aromatherapy on sleep quality: A systematic review and meta-analysis. Complementary Therapies in Medicine. 2019;45:156-66.

57.       van Dalfsen JH, Markus CR. The influence of sleep on human hypothalamic–pituitary–adrenal (HPA) axis reactivity: A systematic review. Sleep Medicine Reviews. 2018;39:187-94.

58.       Friedrich A, Schlarb AA. Let’s talk about sleep: a systematic review of psychological interventions to improve sleep in college students. Journal of Sleep Research. 2018;27(1):4-22.

59.       Mitchell LJ, Bisdounis L, Ballesio A, Omlin X, Kyle SD. The impact of cognitive behavioural therapy for insomnia on objective sleep parameters: A meta-analysis and systematic review. Sleep Medicine Reviews. 2019;47:90-102.

60.       Sosso FAE, Jagannath A, De Oliveira FF, Surani SR, Mysliwiec V. Influence of Socioeconomic Status and Stress Over Quality of Sleep: A Systematic Review. 2018.