Jørgen Eriksen

Individuals reporting long‐term pain in the 1994 and 2000 Danish Health and Morbidity Surveys, which included random samples of 6000 and 16,684 persons respectively, were investigated concerning their use of the health care systems. A considerably higher use was observed in the pain population in the primary as well as the secondary health care sector, compared with a no pain control group. In 1994, individuals reporting long‐term pain had on average 12.8 contacts per year to the primary health care sector compared with 7.3 for the control group. Use of secondary health care sector as estimated by hospital admission frequency and number of in‐hospital days was not only significantly higher for the pain group but showed also an increasing tendency during the periods investigated (1991–1997). Women used the health care system significantly more than men, whereas age did not seem to influence.In conclusion, individuals reporting long‐term/chronic pain have a significantly higher use of the health care system than individuals without long‐term/chronic pain complaints. Reasons may be ascribed to within‐patient factors, factors within the health care system (insufficient knowledge on chronic pain resulting in the seeking after a somatic diagnosis, and difficulties in recognizing the endpoint of reasonable treatment attempts), and societal factors (legislation on disability and compensation).

A 6-year follow-up study of a cross-section of the adult Danish population, based on data from the Danish Health and Morbidity Surveys in 1994 and 2000 is presented. The pain populations were identified through the pain intensity verbal rating scale (VRS) included in the Short Form 36. The 2000 survey also included a question on duration of pain (>6 months). Using this as the 'gold standard', a validation study was performed, which identified the highest accuracy (85%) at the VRS cut-off level: no pain, very mild, or mild pain (control group) versus moderate, severe, or very severe pain (pain group). The cohort comprised 2649 individuals, representative of the Danish population. Prevalence rates of pain in 1994 and 2000 were 13.5 and 15.7%, respectively. The cumulated 6-year incidence of pain development was 10.7%, and the cumulated incidence of pain recovery was 52.1%. During the investigated period, 9.2% of individuals moved from a 'no pain status' to a 'pain status', 7% moved from a 'pain status' to a 'no pain status', and 6.5% maintained their 'pain status'. Significant risk factors for pain development were female gender [odds ratio (OR) 1.5, 95% confidence interval (CI) 1.2-2.0], short education (OR 1.5, CI 1.0-2.2), poor self-rated health (OR 3.3, CI 2.4-4.7), and having at least one long-standing disease (OR 2.6, CI 2.0-3.4). Significant predictors for pain recovery were male gender, younger age, cohabitation status, good self-rated health, good mental health, having no long-standing disease, and having an annual income above 15,400 US dollars.

The present study investigated the ability of sociodemographic variables to predict the short-term effect of multidisciplinary pain treatment in 286 chronic non-malignant pain patients consecutively referred to a Danish multidisciplinary pain centre. At inclusion and 3 and 6 months later the patients' pain and health related quality of life (HRQL) was assessed using self-administered questionnaires. Sociodemographic variables measured were: age, gender, educational level, civil status, employment status and disability pension (DP) status. Intensity of pain was measured using a VAS scale. HRQL was evaluated using the Medical Outcome Study-Short Form (SF-36) and the Psychological General Well-Being Scale (PGWB). Drop out was 30% after 6 months, leaving 170 patients for the study of treatment effects. Among the sociodemographic variables evaluated only retirement pension (RP) and DP-status seemed to be significant outcome predictors: six months after inclusion, patients on RP (patients >68 years, n = 40) reported larger pain reduction (30 mm on the VAS scale) than patients < or =68 years (8 mm on the VAS scale)(P = 0.001). Patients applying for DP-pension (n = 26) did not improve. Patients on DP (n = 54) and patients not receiving DP (n = 50) obtained moderate improvements, but the improvements were significantly larger than the improvements observed in the ApplyDP-group (P = 0.05). The same pattern was seen for changes in psychological well-being (PGWB) and social functioning (SF36-SFA). No improvements were obtained in SF36-Physical functioning scores. DP-status predicted improvement in pain and social functioning even when controlling for the effect of other demographic variables, pain intensity and HRQL at referral. The present study indicates that the multidimensional problems experienced by patients applying for DP are dominated by socioeconomic factors. Focus on solving these socioeconomic problems is important if chronic pain patients are to benefit from multidisciplinary pain treatment.

Opioid effects may be classified as either desirable or undesirable. The undesirable effects, are in the classic sense, termed opioid toxicity or side effects. In the following review, current and new knowledge concerning mechanisms and clinical aspects of the side effects are described and classified. In particular, classification of side effects by their clinical significance in short-term treatment of the opioid-naive patient and long-term treatment of the chronic pain patient is described systematically. Furthermore, new experimental and clinical knowledge of morphine-induced hyperalgesia, allodynia and myoclonus are presented. Finally, the phenomena of tolerance and dependence are discussed.