Chronic pain: One year prevalence and associated characteristics (the HUNT pain study)
Authors: Landmark Tormod , Romundstad Pål , Dale Ola , Borchgrevink Petter C. , Vatten Lars , Kaasa Stein 
Published: August 2013

Abstract

Background
The reported prevalence of chronic pain ranges from 11% to 64%, and although consistently high, the calculated economic burden estimates also vary widely between studies. There is no standard way of classifying chronic pain. We have repeated measurements of pain in a longitudinal population study to improve validity ofthe case ascertainment. In this paper, associations between chronic pain and demographic characteristics, self reported health and functioning, work Incapacity and health care use were investigated in a sample from the general Norwegian population.

Methods
A random sample of 6419 participants from a population study (the HUNT 3 Study) was invited to report pain every three months during a 12 month period. Chronic pain was defined as moderate pain or more (on the SF-8 verbal rating scale) in at least three out of five consecutive measurements. Self reported health and functioning was measured by seven of the eight subscales on the SF-8 health survey (bodily pain was excluded). Health care utilisation during the past 12 months was measured by self report, and included seeing a general practitioner, seeing a medical specialist and seeing other therapists. The survey data was combined with information on income, education, disability pension awards and unemployment by Statistics Norway, which provided data from the National Education database (NUDB) and the Norwegian Labour and Welfare Administration (NAV).

Results
The total prevalence of chronic pain was 36% (95% CI34-38) among women and 25% (95% CI 22–26) among men. The prevalence increased with age, was higher among people with high BMI, and in people with low income and low educational level. Smoking was also associated with a higher prevalence of chronic pain. Subjects in the chronic pain group had a self-reported health and functioning in the range of 1–2.5 standard deviations below that of those without chronic pain. Among the chronic pain group 52% (95% CI 49–55), of participants reported having seen a medical specialist during the 12 month study period and 49%(95% CI 46–52) had seen other health professionals. The corresponding proportions for the group without chronic pain were 32% (95% CI 29–34) and 22% (95% CI 20–25), respectively. Work incapacity was strongly associated with chronic pain: compared with those not having chronic pain, the probability of being a receiver of disability pension was four times higher for those with chronic pain and the probability of being unemployed was twice has high for those with chronic pain. The population attributable fraction (PAF) suggested that 49% (95% CI 42–54) of the disability pension awards and 20% (13–27) of the unemployment were attributable to chronic pain.

Conclusion and implications
Chronic pain is a major challenge for authorities and health care providers both on a national, regional and local level and it is an open question how the problem can best be dealt with. However, a better integration of the various treatments and an adequate availability of multidisciplinary treatment seem to be important.