Sleep is defined medically as a physiologic state of relative unconsciousness and inaction of the voluntary muscles, the need for which occurs periodically. Another definition describes sleep as a "natural and periodic state of rest during which consciousness of the world is suspended." Sleep is no longer considered a passive state but rather a highly active process with brains and bodies undergoing a variety of changes in the transition from sleep to wakefulness.
As to the question of whether it is necessary, sleep has been shown to be beneficial in aiding immune function, metabolic control, learning, memory, mood and essential bodily functions. It is also essential for emotional stability. Lack of sleep impacts health, behaviour, emotional control and responses, safety, longevity and cognition. Chronic sleep deprivation may result in poor health, diseases such as diabetes, hypertension, cardiovasulcar disease, obesity, mood disorders, and early mortality.1,2
The time requirement for sleep diminishes with aging. Infants sleep from 16 to 20 hours a day; children between the ages of one and four about 11 or 12 hours a day; adolescents, with a different sleep cycle, need about 9 hours; and the elderly tend to require less sleep than young adults.
Diseases, particularly respiratory diseases such as asthma, chronic obstructive pulmonary disease and obstructive sleep apnea, have a major impact on sleep. In asthma, symptoms indicating poorly-controlled or uncontrolled asthma will occur at night. There is a physiological basis for nocturnal symptoms which can result in frequent awakenings which in turn decrease the quality of life and increase mortality. Nocturnal symptoms may be due to a late phase reaction or to the presence of triggers in the bedroom.
Sleep is crucial to well-being. Interrupted sleep, sleep disorders and poor quality of sleep result in negative moods, lethargy, reduced focus and concentration, reduced alertness, confusion, sleepiness, fatigue, loss of vigour and poor health. Lack of sleep or disturbed sleep will affect how the individual functions, and his or her emotional state, motivation, relationships and conduct. It also impedes decision-making, concentration and reaction time, reduces learning, affects memory and increases cognitive errors. School and job performance are deeply affected. The neuro-cognitive deficiencies due to sleep deprivation tend to amass over time.3
Asthma often presents with nocturnal symptoms. Is the wheezing at night connected to disturbed sleep and to increased daytime symptoms? Desager and colleagues4 sought to answer that questions by examining a random sample of 1,234 children between the age of 6 and 14. Using the International Study of Asthma and Allergies in Childhood questionnaire together with a sleep questionnaire they found that daytime fatigue and sleepiness were more common in children who wheeze than in those who did not. They found that chronic cough, snoring, chronic rhinitis and eczema were associated with disturbed sleep; with chronic rhinitis a risk factor for snoring in children who wheezed. They concluded that upper airway symptoms were related to sleep disturbances and children who wheezed had both a decreased quality of sleep and increased daytime tiredness and sleepiness.
Sadeh and colleagues found a strong relationship between asthma severity and sleep quality in children with asthma. Variability between morning and evening peak flow measures was significantly correlated with both subjective and objective measures of sleep. Poor sleep was associated with decreased pulmonary function. Besides diminished quality of sleep, the children with asthma also suffered from increased fatigue and reduced alertness.5 Another study of children with asthma found that those with significant sleep disturbances tended to have psychological problems and to perform poorly on both tests of concentration and memory.6
Tobacco smoke is a noted trigger of asthma. Yolton and colleagues7 studied the effect of second hand smoke (SHS) and sleep patterns in children with asthma whose parents smoked at home. After adjusting for gender, age, race, maternal education, marital status, income, education, prenatal tobacco exposure and maternal depression, and other possible confounding factors, they found that exposure to SHS resulted in children having sleep-related problems such as delayed onset, sleep disordered breathing, daytime sleepiness, sleep disturbance and parasomnias. Parasomnias are a type of sleep disorder involving abnormal movement, emotions, perceptions, behaviours, and dreams that tend to occur while falling asleep, or while sleeping, or between sleep stages, or during waking.
A study by Janson and colleagues8 examined the prevalence of sleep disturbances and daytime sleepiness in patients with asthma. A random European population of 2,202 adults, aged 20 to 45, together with 459 patients with suspected asthma, was studied using interviews, methacholine challenge, skin prick testing and questionnaires. Peak flow readings were also recorded for one week.
The investigators found that patients with asthma were twice as likely as patients without asthma to have difficult falling asleep, early morning awakening and daytime sleepiness. They also found a significant correlation between sleep disturbances and the number of asthma-related symptoms. These patients also scored lower on levels of sleep efficiency. Both sleep efficiency and time awake at night positively correlated with peak flow variability. Quality of sleep was also impacted by nocturnal symptoms, while bronchial hyperresponsiveness was independently related to daytime fatigue. Further, they found that allergic rhinitis, reported by 71% of the patients with asthma, was independently related to difficulty falling asleep (OR 2.0) and was an important underlying cause of sleep impairment. Asthma and day time sleepiness was related (OR 1.6) as was allergic rhinitis (OR 1.3).
Fatigue and sleepiness accompany disturbed sleep. Siroux and colleagues9 evaluated the quality of life in a general population of patients with asthma. They used the AQLQ (Asthma Quality of Life Questionnaire) in combination with an asthma severity scale, clinical items, FEV1, and asthma severity components (such as frequency of exacerbations and hospitalizations) to determine both physical and mental health. As expected, compared with the general population, patients with asthma scored lower on the physical and mental component scores. The researchers concluded that nocturnal symptoms, as well as asthma severity, had an independent impact on the quality of life.
. . . To be continued
OR – odds ratio
Fev1 – Forced Expiratory Volume in One Second
- Sleep and Disease Risk http://healthysleep.med.harvard.edu/healthy/matters/consequences/sleep-and-disease-risk Accessed August 2015
- Yoo SS, Gujar N, et al. The human emotional brain without sleep--a prefrontal amygdala disconnect. Curr Biol. 2007 Oct 23;17(20):R877-8.
- Durmer JS, and Dinges DF. Neurocognitive consequences of sleep deprivation. Semin Neurol. 2005;25(1):117-129.
- Desager KN, Nelen V, Weyler JJ, De Backer WA. Sleep disturbance and daytime symptoms in wheezing school-aged children. J Sleep Res. 2005;14(1):77-82
- Sadeh A, Horowitz I et al. Sleep and pulmonary function in children with well-controlled, stable asthma. Sleep. 1998; 21(4): 379-84.
- Stores G, Ellis AJ et al. Sleep and psychological disturbance in nocturnal asthma. Arch Dis Child. 1998; 78(5): 413-9. Abstract.
- Yolton K, Xu Y et al. Associations between secondhand smoke exposure and sleep patterns in children. Pediatrics 2010; 125(2):e261-8. doi: 10.1542/peds.2009-0690. Abstract.
- Janson C, De Backer W, P et al. Increased prevalence of sleep disturbances and daytime sleepiness in subjects with bronchial asthma: a population study of young adults in three European countries. Eur Respir J. 1996;9(10):2132-8
- Siroux V, Boudier A, Anto JM, et al. Quality-of-life and asthma-severity in general population asthmatics: results of the ECRHS II study. Allergy. 2008;63(5):547-54