Key points

• Around 15 per cent of adults suffer from insomnia. The prevalence is higher among women and the elderly.
• The prevalence of insomnia in Norway has increased since 2000.
• On average, adults sleep for around seven hours per night.
• Insomnia increases the risk of health problems, sick leave and accidents.

About sleep and sleep problems 

Sleep is vital for good health. In recent years, we have gained a better understanding of the importance of sleep, both from an individual and public health perspective. Poor quality or insufficient sleep can negatively affect a person’s mood, concentration and performance.

• Sleep disorders can be divided into a number of subgroups: Insomnia is the most common sleep disorder. The core symptoms of insomnia are difficulties in initiating or maintaining sleep, as well as impaired daytime functioning. 
• Delayed sleep phase syndrome is characterised by considerable difficulty in getting to sleep at the normal time.
• Sleep apnoea is characterised by repeated breathing cessations (apnoea) during sleep, often accompanied by loud and intense snoring.
• Parasomnias are sleep disorders involving undesirable physical events or experiences during sleep.
• Narcolepsy is a rare sleep disorder characterised by increased drowsiness and seizures with abnormal sleepiness during the day.

Background data

The description of the prevalence of sleep disorders is based on Norwegian and international research reports.

Prevalence of sleep disorders amongst adults

Insomnia – status and development over time

Surveys from many countries show that nearly a third of the population experiences sleep problems on a weekly basis. Recent figures from Norway indicate that over half of patients being treated by the primary care service are experiencing sleep problems (Bjorvatn, 2017). Half of patients treated by the mental healthcare service also report symptoms of insomnia (Reigstad, 2010; Shochat, 1999). Only a few cases are identified by a healthcare professional (Sivertsen, 2010).

Previous studies have shown that approximately 10 per cent of the adult population in the Western world, including Norway, meet the diagnostic criteria for insomnia (Ohayon, 2002; Uhlig, 2014). 

The prevalence of insomnia amongst adults appears to have increased. A Norwegian survey recently showed an increase from 11.9 per cent to 15.5 per cent from 2001 to 2011 (Pallesen, 2014). The increase was particularly evident amongst women aged between 45 and 60 and primarily concerned problems associated with falling asleep, dissatisfaction with quality of sleep, and reduced daytime functioning due to poor sleep.

Despite the increased prevalence of insomnia, an international literature summary shows that there is no evidence for arguing that the adult population sleeps less today than in the 1960s (Bin, 2012). The average duration of sleep amongst the participants in the Hordaland Health Survey (adults) was 6 hours and 52 minutes for men and 7 hours and 11 minutes for women (Ursin, 2005), which closely matches international estimates.

The circadian rhythm of Norwegians has changed since 1980. We tend to go to bed later in the evening and get up later in the morning (Sivertsen, 2011b).

Other sleeping disorders

Sleep apnoea: The prevalence of sleep apnoea in Norway is between 8 and 16 per cent, depending on severity (Hrubos-Strom, 2011). This corresponds with international findings (Young, 1993).

Narcolepsy: Narcolepsy is a very rare disease with a prevalence of approximately 2 in 10,000 (Heier, 2009). Following swine influenza vaccination with Pandemrix in 2009, several dozen Norwegians developed narcolepsy. Most of these were children and adolescents (Heier, 2013; Trogstad, 2017). 

Parasomnias: A 2010 survey of 1 000 Norwegians revealed major differences in the prevalence of various forms of parasomnias (Bjorvatn, 2010). The most common parasomnia (at least one incident during the past three months) were nightmares (19 per cent), sleep talking (18 per cent) and so-called "sleep-related grunting" (14 per cent). In addition, it is estimated that around 20 - 30 per cent of the population has sleepwalked at least once during their lifetime, usually as a child. Approximately 1-2 per cent of the adult population sleepwalks occasionally.

Gender differences

Sleep problems are more common in women than in men, and both the prevalence and gender differences appear to increase with age (Sivertsen, 2009a).

Seasonal influences

It is a common assumption that sleep varies with the seasons and changes in daylight but there is no unequivocal evidence to suggest that the prevalence of insomnia changes, or that duration of sleep varies during the year (Friborg, 2012; Johnsen, 2012; Sivertsen, 2011a). These surveys also show no seasonal differences in sleep duration.

Sleep and sleep problems in adolescents

Many Norwegian adolescents appear to sleep too little. Studies show that:

• Adolescents sleep for just under 6.5 hours per night on weekdays compared with the recommended 8-9 hours (Hysing, 2013).
• There was a general increase in sleep disorders amongst adolescents from 1983 to 2005 (Pallesen, 2008).
• One in four Norwegian adolescents meets the formal criteria for an insomnia diagnosis. Insomnia is more common amongst girls than boys (Hysing, 2013).

The results of these Norwegian studies are consistent with international findings showing that sleep duration amongst 10- to 15-year-olds decreased by 23-44 minutes during the period from 1985 to 2004, primarily as a result of going to bed later (Dollman, 2007).

Delayed sleep phase syndrome

Some adolescents and young adults suffer from delayed sleep phase syndrome. This means that they have considerable difficulty falling asleep at the normal time, often not until after two o'clock in the morning, and that they find it very difficult to wake up (Solheim, 2014). However, adolescents have few problems staying asleep. If they are not woken up, they can continue sleeping long into the day.

Between three and eight per cent of adolescents have delayed sleep phase syndrome, with the precise prevalence depending on the definition applied (Saxvig, 2012; Sivertsen, 2013). By comparison, the prevalence amongst adults is less than one per cent (Schrader, 1993).

Sleep problems in babies and children

A number of studies from Western countries indicate that children and adolescents sleep less now than a few decades ago (Iglowstein, 2003; Matricciani, 2012; Thorleifsdottir, 2002).

Education-related differences

Amongst adults, insomnia is linked to education level and income.  

• Symptoms of insomnia are more than twice as common amongst people with a low education (about 20 per cent) compared with those with a higher education. The prevalences are approximately 20 per cent compared with around 10 per cent. (Sivertsen, 2009a).
• Insomnia is more common amongst children from families with a low income than amongst those from high-income families. The prevalences are 28 per cent compared with 10 per cent. (Bøe, 2012).
• Both insomnia and short sleep duration are more common amongst 16- to 19-year-old adolescents from families whose parents have a lower education, are unemployed or have a low income, compared to adolescents from families with a higher education and income (Hysing, 2017).

Risk factors for sleep problems

Noise: Sleep problems linked to noise are discussed in the section on noise in the Public Health Report.

Chronic illness: Sleep problems often occur alongside other health problems. For example, children with a chronic illness, particularly neurological conditions, tend to experience more sleep problems than healthy children (Hysing, 2009).

Mental disorders: Sleep problems are very common amongst young people (Sivertsen, 2014a) and adults (Sivertsen, 2012) with mental disorders. Although sleep problems are widespread amongst patients being treated by the mental healthcare service in Norway, they are rarely diagnosed (Kallestad, 2011).

Shift work: People who work shifts and nights are more prone to sleep problems and other health issues. In particular, there seems to be an increased risk of sleep problems if a person’s rota involves nightwork and short breaks between shifts (Vedaa, 2016).

Pregnancy: Sleep problems are common amongst pregnant women (Dorheim, 2012) and it is not uncommon for sleep to remain poor for a long time after birth. While six out of ten women met the diagnostic criteria for insomnia both during week 32 of pregnancy and eight weeks after birth, 40 per cent still had insomnia two years later (Sivertsen, 2015d).

Children’s bedtime routines

Amongst the very youngest children, a high degree of parental involvement with bedtime routines (e.g. rocking until the child falls asleep or feeding just before bedtime) is linked to sleep problems because it hinders children’s ability to regulate their own sleep and wakefulness (Sadeh, 2010).

Co-sleeping has been linked to the development of sleep problems over time, even after taking the child's previous sleep problems into account (Hysing, 2014). The longer the child shares a bed with their parents, the greater the risk of short sleep duration and more frequent waking at 18 months of age.

Screen use

The increased use of electronic items (mobile phones, tablets, video games, etc.), particularly before bedtime, is closely linked to sleep problems (Hysing, 2015b). A study of Norwegian high school students showed that using tablets, smartphones and computers during the last hour before bedtime increased the risk of shorter sleep duration (Hysing, 2015b).

Stress

A poor working environment is also strongly linked to sleep problems (Linton, 2015). Social support at work, control over one’s own job situation and a perception of fairness help to protect against the development of sleep problems (Linton, 2015). However, high levels of stress, bullying at the workplace and a perception of injustice were linked to a higher risk of developing sleep problems.

Hereditary factors

Both hereditary and environmental factors appear to be important in explaining the development of sleep problems. With regards to the significance of hereditary factors, little research has so far been conducted into the possible genetic causes of sleep problems, although studies of families and twins have shown an accumulation of sleep problems in some families (Gehrman, 2013). Most of these studies estimate the genetic contribution to be somewhere between 25 per cent and 45 per cent, depending on the definition and type of sleep problem (Gehrman, 2013).

The fact that the prevalence of insomnia has increased considerably in Norway during the past ten years also suggests that environmental factors and habits can play a significant role in the development of sleep problems.

Preventing sleep problems

It is believed that knowledge and advice concerning sleep hygiene can help prevent the development of sleep problems (Yang, 2010). However, little research-based knowledge is available concerning preventive measures to combat sleep problems, with a few exceptions:

• Preventive measures among young children may have an effect (Paul, 2016)
• There is evidence to suggest that behavioural interventions for insomnia amongst children have a positive effect (Meltzer, 2014).
• Educational programmes about sleep amongst adolescents have little preventive effect (Cassoff, 2013).
• Adolescents who start their school day later in the morning tend to sleep longer and function better at school (Vedaa, 2012).

Most people with sleep problems (about 80 per cent) also suffer from mental or physical illness/disorder. It has therefore been common to look at the prevention of sleep problems as part of the measures associated with these conditions. While the prevention of anxiety and depression, for example, will probably also have a transferable effect on sleep problems, there is still a strong need for future studies to investigate the effects of preventive measures which are targeted more at sleep problems. 

As sleep problems are very common and the consequences are substantial, we need to improve our understanding of how sleep problems can be prevented and treated.

Consequences and challenges

Amongst children, short sleep duration and nocturnal waking are linked to higher levels of emotional difficulties, behavioural problems and a higher risk of developing mental problems compared with children who sleep well, even after taking other causal explanations into account (Hysing, 2016c; Sivertsen, 2015c; Steinsbekk, 2013).

For adolescents, findings from Norway show that both insomnia and short sleep duration are associated with an increased risk of:

• mental problems and disorders (Hysing, 2016b; Sivertsen, 2014a; Sivertsen, 2015b)
• self-harm (Hysing, 2015c)
• drug and alcohol problems (Sivertsen, 2015f)
• overweight/obesity (Sivertsen, 2014c)
• school absence (Hysing, 2015a; Sivertsen, 2013)
• poor academic performance (Hysing, 2016a; Sivertsen, 2015a)

Amongst adults, sleep problems impact on health in many areas (Sivertsen, 2015e; 2014b):

• Insomnia increases the risk of lower pain tolerance (Sivertsen, 2015e).  
• Insomnia is associated with reduced work capacity, and doubles the risk of sick leave and permanent work disability (Sivertsen, 2006; Sivertsen, 2009b).
• Insomnia also increases the risk of accidents and mortality (Leger, 2010).

Many people do not seek help

Almost 60 per cent of those suffering from insomnia never seek help for their problems and thus remain untreated (Morin, 2006). This is of particular concern given that we know that 70 per cent of people with insomnia still meet the criteria for diagnosis one year later and 50 per cent after three years (Morin, 2009).

Socioeconomic consequences

In the USA, the economic costs associated with insomnia are estimated to amount to over USD 90 billion a year. This includes both direct medical costs, and indirect costs such as sleep-related accidents and lost work capacity (Kessler, 2011). No corresponding estimates are available for Norway.

Treating sleep problems

Drug therapy is still the most frequently used form of treatment for insomnia (Sivertsen, 2010). This is despite the fact that non-pharmacological  interventions such as cognitive-behavioural therapy (CBT) have better and longer-lasting effects (Morin, 1994; Pallesen, 1998). According to the American College of Physicians, CBT should be the first choice for the treatment of insomnia (Qaseem, 2016).

CBT involves the provision of training about how sleep is influenced by lifestyle factors such as physical exercise, food intake and alcohol, and why various environmental factors such as light, noise and temperature are important. Sleep restriction, stimulus control and relaxation techniques are also important elements of CBT for insomnia. The techniques are relatively simple and can in principle be used by most healthcare professionals.

Access to such treatment is limited by capacity. Recent surveys suggest that self-help programmes, either in the form of a book (Bjorvatn, 2011) or online (Hagatun, 2017) can have a good effect. International literature summaries also conclude that online self-help CBT is effective (Zachariae, 2015). 

In Norway, a number of medications are prescribed for the treatment of insomnia. Although many sleep medications (hypnotics) have a well-documented short-term effect and can be useful for treating acute insomnia, none of them solves the underlying cause of the sleep problem. We also know that many people with insomnia are unaware of the available treatment options and many use alcohol, alternative therapies and undocumented health food products in an attempt to improve their sleep (Morin, 2006).