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Chronic pain

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Chronic pain affects about 30 per cent of the adult Norwegian population and is the most common reason for long-term sick leave and disability benefit.

Chronic pain affects about 30 per cent of the adult Norwegian population and is the most common reason for long-term sick leave and disability benefit.


illustrasjon pain
Pain in the muscles and joints is the most common type of chronic pain. Sleep problems, long-term sick leave and disability are associated with chronic pain. Copyright: Norwegian Institute of Public Health/fetetyper.no

Main points

  • About 30 percent of the Norwegian population report that they have chronic pain.
  • There has been a slight increase in the prevalence of chronic pain in recent years.
  • More women than men are affected.
  • Pain in the musculoskeletal system is the most common type of chronic pain.
  • Approximately 50 per cent of cases of disability benefits can be attributed to chronic pain, according to the health surveys in Trøndelag and Tromsø.
  • Many cases of long-term sick leave are due to chronic pain.

Definition

Chronic pain is defined as pain that persists for more than three months (Treede, 2015).

Data sources

The health survey in Nord-Trøndelag (HUNT), the Tromsø Study, and statistics from NAV (the Norwegian Labour and Welfare Administration) are sources for data on the prevalence of chronic pain in the population as well as consequences of chronic pain conditions.

The Norwegian Prescription Database is the source of data on drug use.

In addition, various research reports are used, see references in the text.

Prevalence of chronic pain in Norway

  • About 30 per cent of the adult population in Norway report that they have chronic pain (Breivik, 2006; Landmark, 2012; Rustoen, 2004). The percentage receiving treatment for their pain condition is unknown.

Prevalence estimates vary considerably nationally and internationally, probably as a result of differences in methodology and definitions (Steingrimsdottir, 2017).

  • Pain is probably the most common reason for patients visiting their general practitioner (GP).

In Sweden, 28 per cent of patients visiting their GP have one or more pain-related diagnoses (Hasselstrom, 2002). See Figure 1.

Corresponding figures are shown from Denmark (Eriksen, 2003), from Norway there are no data. In Denmark, patients suffering from chronic pain spend four to five times more days in hospitals compared to the rest of the population (Becker, 1997).

diagram

Figure 1. Prevalence of chronic pain in different age groups in the Tromsø survey 2007-2008 and 2015-2016. Source: The 6th and 7th Tromsø survey. Click to enlarge figure.

More women than men are affected

More women than men suffer from chronic pain (Fillingim, 2009; Steingrimsdottir, 2017). Gender differences are modest for pain in general, but significantly greater for pain that effects many parts of the body (Mansfield, 2016), see Figure 2.

These gender differences are reflected in the disability statistics, where more than twice as many women as men have muscular or skeletal disease as the main diagnosis (NAV.no). For such diseases, pain is usually the most important and sometimes the only symptom.

Gender differences are also found in laboratory experiments measuring pain sensitivity (Ostrom, 2017) and are seen in animals (Sorge, 2017). Increased pain sensitivity is believed to be an important risk factor for development of chronic pain (Greenspan, 2013).

Animal research suggests that differences for both acute and chronic pain depend on gender differences in the immune system (Sorge, 2011; Sorge, 2015).

diagram

Figur 2. Percentage of women and men with chronic pain. Bottom: pain sensitivity. Widespread chronic pain defined as pain that affects at least 5 of 15 body locations. Strong chronic pain defined as pain intensity of 6 or more on a scale of 0-10.
Pain sensitivity is measured by cold stimulation of the hand, where people who interrupted before 106 seconds are considered to have increased pain sensitivity.
Source: Tromsø survey (Tromsø 6, 2007-08).

Click to enlarge figure.

Prevalence in different age groups

The prevalence of many pain-related disorders, such as osteoarthritis, become more common with increasing age (Zhang, 2010). The use of analgesics also increases with age, with the greatest increase up to the age of 40-50 years, see Figure 3a-b. For some conditions, however, there is a decrease at higher age, for example the incidence of migraine in women which declines after the age of 50 (Buse, 2012; Pavlovic, 2017).

Overall, most health surveys show that the prevalence of chronic pain is stable in the higher age groups (Fillingim, 2017).

In the oldest and the youngest age groups, there is great uncertainty concerning the prevalence of chronic pain. This is due to low participation rates in health surveys among younger and older age groups. In hospitals and nursing homes drug use is not registered at the individual level.

The prevalence of chronic pain in people with dementia living in nursing homes is probably under-reported and may be misdiagnosed as anxiety and agitation (Husebo, 2011).

diagram
diagram

Figur 3a, 3b.  The percentage of men and women in different age groups who received prescription analgesics in 2016. Analgesics are often classified as non-opioids and opioids (morphine-like substances). Source: The Norwegian Prescription Registry. Click to enlarge figures.

Trends

Although effective treatments have been developed in recent decades for some pain conditions such as arthritis and migraine, there is no evidence that treatment has led to a lower prevalence of chronic pain in the population. On the contrary, data from the Tromsø survey indicate a slight increase in recent years (see figure 1).

Differences between Nordic countries

In a comparison of 15 European countries, Norway had the highest prevalence of chronic pain (Breivik, 2006). In this study the prevalence of moderate to strong chronic pain was around 30 per cent in Norway, while the corresponding figures in the other Scandinavian countries were 16-19 per cent, see figure 5. This study has methodological weaknesses, and the findings are uncertain.

Socioeconomic differences

  • There is a clear correlation between chronic pain and socioeconomic factors such as education, income, and occupational status, the prevalence of chronic pain is higher in low socioeconomic groups (Bonathan, 2013).
  • Regular use of strong analgesics (opioids) is seen more frequently in people with lower income and educational level (Svendsen, 2014).

Little is known about the factors contributing to the social differences. On the one hand, workload and lifestyle among those with low income and education can contribute to pain. For example, back pain is more common among people with heavy physical work, while neck pain is more common among people with sedentary work (Veiersted, 2017). On the other hand, chronic pain can lead to drop-out from education and work.

Burden of disease 

Burden of disease. Although the burden of disease for chronic pain has not been calculated, the data for different pain conditions show that pain conditions are the main cause of years lived with disability in Norway. Muscular and skeletal disorders and migraine account for more than a quarter of the loss of health (NIPH, 2017). Similar results have been found internationally (GBD 2015 Disease and Injury Incidence and Prevalence Collaborators, 2016).

Mortality. Chronic pain is associated with increased mortality. The evidence for this is particularly strong when it comes to chronic widespread pain. A meta-analysis of studies involving more than half a million individuals found about 2.5 times higher mortality in people with chronic widespread pain (Macfarlane, 2017).

In people with chronic widespread pain, mortality from cardiovascular and respiratory diseases is particularly pronounced, while the effect on cancer mortality is less clear. Part of the association can be explained by unhealthy lifestyle, but even when this is taken into account, mortality from cardiovascular and lung diseases is almost twice as high among people with widespread pain.

Suicide. Chronic pain is associated with significantly increased suicide risk and this increased risk occurs independently of mental health, socioeconomic factors and substance abuse (Racine, 2017).

Sick leave and disability

Muscular and skeletal disorders are the main diagnosis for 35-45 per cent of sick leave certified by doctors in Norway and are the registered diagnoses in 29 per cent of disability benefit cases (NAV.no). Figures for other pain conditions are not available.

Population surveys indicate that the above figures are too low. Both the Health Survey in Nord-Trøndelag and the Tromsø Survey show that around 50 per cent of the disability cases can be attributed to chronic pain (Landmark, 2013; Nielsen, 2013). In 2017, 325 900 received disability benefits (NAV.no).

Total social costs. Analysis of the societal cost of chronic pain has not been carried out in Norway. A thorough analysis in the USA concluded that chronic pain costs society at least 4.3 per cent of gross domestic product annually (IOM, 2011). In Norway this would correspond to at least NOK 135 billion annually (based on 2015 figures).

Causes and risk factors   

Genetic factors

The genetic contribution varies greatly and is highest for fibromyalgia and migraine where around 50-60 per cent of the risk can be attributed to genetic factors (Nielsen, 2012). Other conditions, such as irritable bowel syndrome, appear to be less dependent on genetic predisposition.

Pain sensitivity 

Chronic pain patients have increased pain sensitivity compared with the general population (Joharatnam, 2015; Plesner, 2018; Stabel, 2013). It is uncertain whether increased pain sensitivity is a cause or a consequence of chronic pain.

Side effects of treatment

For some surgical procedures, up to half of the patients develop chronic pain (Kehlet, 2006).

For some chemotherapeutic agents the majority of patients develop chronic neuropathic pain (Brozou, 2017). With increasing numbers of cancer survivors, this is a growing challenge for patients and health services.

Other factors:

  • Occupation: Lower back pain is more common in occupations involving heavy physical labour (Tynes, 2008).
  • Obesity increases the load on the skeleton and thus increases the risk of a number of pain conditions in the musculoskeletal system. There is also evidence that obesity affects pain through immunological mechanisms (Arranz, 2014).
  • Nicotine has a weak and short-term analgesic effect but daily smoking is likely to be associated with an increased risk of prolonged pain (Ditre, 2011).
  • Anxiety and depression: Twin studies indicate that common genetic risk explains the high comorbidity between chronic pain, anxiety and depression (Burri, 2015; Vassend, 2017).
  • Sleep problems are associated with increased prevalence of chronic pain and increased pain sensitivity (Sivertsen, 2015)
  • Immunological (inflammatory) mechanisms contribute to many pain conditions (Backryd, 2017; Linnman, 2011).

Challenges for public health

Chronic pain is the cause of many cases of disability benefits and long-term sick leave. We need more knowledge about causes and preventive measures.

 

References

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