The Course of Low Back Pain From Adolescence to Adulthood

Eight-Year Follow-up of 9600 Twins

Lise Hestbaek, DC, PhD; Charlotte Leboeuf-Yde, DC, MPH, PhD; Kirsten Ohm Kyvik, MD, PhD; Claus Manniche, Dr. Med Sci

Disclosures

Spine. 2006;31(4):468-472. 

In This Article

Discussion

The pattern demonstrated in this study is similar to that demonstrated in adults,[1,2,3] with one exception. There are, despite a large number remaining in the group with more than 30 days of LBP, 33% with persistent LBP at baseline who are symptom-free at follow-up, compared with only 9% found in an adult population.[2] This might reflect a specific subgroup of LBP that is active in early years but nonsymptomatic in adults. Previous population-based MRI studies of 13- and 40-year-olds showed that endplate defects are associated with pain in children but not in adults.[25,26] We therefore speculate that this could represent one etiologic explanation of the relatively large group of children, who recover from persistent LBP.

In accordance with previous studies,[11,12,13] we also found LBP at baseline to be a significant predictor for LBP at follow-up. We further demonstrated a dose-response association between number of days with LBP at baseline and the occurrence of LBP at follow-up, i.e., the more days with LBP at baseline, the higher the risk of future LBP. To our knowledge, this has not been shown before.

Our cohort has two major strengths: its large sample size and the fact that it covers the transition from childhood into adulthood. It could be argued that the spread in age of the cohort represents a problem, i.e., the development from 12 to 20 years of age is significantly different from that of 22 to 30. However, when results are stratified for age, there is no difference between groups; therefore, we do not consider this to devaluate our results. The response rate of our study is not completely satisfying, but the fact that 96% of responders answered the LBP-questions diminishes the risk of disease-specific bias. With regard to representativeness, the overrepresentation of people with LBP-year at baseline must be considered, when comparing the 1-year prevalence in 1994 with that from 2002. This could lead to an inflated estimate for 2002 compared with the target population. Fortunately, the equal distribution of persistent LBP among responders and nonresponders lend credibility to our results relating to this variable. Likewise, the transition in LBP status is equal for males and females; thus, the female overrepresentation is unlikely to influence our results.

Finally, we found long-term recall to be of limited value. Researchers should take the large number of forgotten episodes of LBP (at least 35%) into account in future studies. These findings are in line with other studies, where lifetime history of LBP has proven unreliable. Burton et al reported that 60% of adolescents forgot previous episodes of pain;[27] and in a study by Szpalski et al,[10] 50 of 51 children reporting LBP within the past 2 years also reported having had LBP the day before examination. As it is highly unlikely that 98% of all LBP cases during the previous 2 years involved the same day, such a pattern of reporting must indicate severe recall bias. Therefore, we feel confident that the problem is related to long-term recall, rather than to the quality of the used questionnaire. Therefore, the poor validity of the variable does not affect the validity of our study, since the lifetime prevalence variable was used only for validation purposes in our analyses.

Our results leave no doubt that LBP, and especially persistent LBP, at an early age is a strong predictor of persistent LBP later in life with odds ratios as high as 4, and that the importance of early LBP as a risk factor is independent of both age and gender. This indicates that our findings are not specifically linked to adolescence but can be applied to all incidence cases of LBP regardless of age, bearing in mind that the majority of incidence cases occur before the age of 20 years. In clinical practice, this line of thought could lead to more attention to first-time cases of LBP, regardless of severity, to prevent later chronicity. It might be counterproductive to postpone treatment/prevention until the problems become more severe and chronic.

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