Comorbidity with low back pain - A cross-sectional population-based survey of 12-to 22-year-olds

Study Design. Cross-sectional, population-based survey. Objectives. To investigate the pattern of comorbidity with low back pain in adolescents. Summary of Background Data. Low back pain is usually dealt with as a specific and independent entity. However, the existing literature shows comorbidity to be common with low back pain, suggesting that low back pain may be part of a broader pattern of general health. The present knowledge is based on studies of adult populations; therefore, associations could be explained by work and lifestyle factors. Information in this area is lacking regarding subjects still unaffected by such factors. Methods. A questionnaire-survey about general health, including low back pain, was carried out among twins registered in the population-based Danish Twin Registry. Associations between disorders were calculated and patterns of comorbidity investigated, by means of logistic regression and a finite mixture model. Finally a twin-control study was conducted. Results. A total of 9,567 individuals, 12 to 22 years of age, responded to the questionnaire. Positive associations between low back pain and asthma and headache/ migraine were demonstrated, mainly because of study participants with several disorders. No association between low back pain and atopic dermatitis/hay fever was found. The presence of two other disorders increased the probability of low back pain considerably more than the presence of only one other disorder. The finite mixture model indicated that the probability of belonging to a frail subgroup decreased from 60% at age 13 to 25% at age 21, and in the frail subgroups nearly all report low back pain and headache in the older ages. Furthermore, increasing duration of low back pain increased the likelihood of having other disorders. Results from the twin-control study were similar. Conclusion. Young people are more likely to suffer from asthma and headache, but not from atopic dermatitis/ hay fever, if they have low back pain. All of the investigated disorders cluster in some individuals. A model of common origin for these seemingly independent disorders should be considered.