Study design: A retrospective cohort study.
Objective: To describe the incidence and duration of low back pain in patients from the general working population in Norway who take at least 2 weeks of compensated absence from work.
Summary of background data: There is a growing concern about the proportion and socioeconomic consequences of work absence resulting from low back pain, and exact figures on incidence and duration of work incapacity from low back pain in the general working population are needed.
Methods: Cases were identified from files of the national medical insurance system, covering 90% of all employees in Norway. A total of 89,190 patients with low back pain were identified in 1995 and 1996, based on the International Classification of Primary Care (ICPC codes L02, L03, L84 and L86). Census data were used for the denominators.
Results: The estimated overall 1-year incidence was 2.27%. It was significantly higher for women (2.72%) than for men (1.91%). The incidence increased with increasing age. The median (25th-75th percentile) duration of absence for all claimants was 43 days (25th-75th percentile, 23-103). Approximately 35% of claimants returned to work after 1 month, 70% had returned after 3 months, and 85% had returned after 6 months. Thirty percent of all claimants had low back pain with radiation, and the median duration of absence for these was 59 days (25th-75th percentile, 28-152 days) versus 38 days (25th-75th percentile, 21-86 days) for claimants without radiating pain (P < 0.001).
Conclusion: The results of this study reaffirm the burden of low back pain to society. The data show that the prognosis for the majority of this group of patients with low back pain, even for those with radiating symptoms, is generally good. From 6 to 20 weeks after onset, however, the return-to-work curve declined steeply among the individuals studied. Approximately 42% of those still off work after 6 months had not returned to work after 12 months, and were switched to permanent disability pension or other compensation forms.