Michele C. Battié

A prospective study of work perceptions and psychosocial factors affecting the report of back injury

A longitudinal, prospective study was conducted on 3,020 aircraft employees to identify risk factors for reporting acute back pain at work. The premorbid data included individual physical, psychosocial, and workplace factors. During slightly more than 4 years of follow-up, 279 subjects reported back problems. Other than a history of current or recent back problems, the factors found to be most predictive of subsequent reports in a multivariate model were work perceptions and certain psychosocial responses identified on the Minnesota Multiphasic Personality Inventory (MMPI). Subjects who stated that they “hardly ever” enjoyed their job tasks were 2.5 times more likely to report a back injury (P = 0.0001) than subjects who “almost always” enjoyed their job tasks. The quintile of subjects scoring highest on Scale-3 (Hy) of the MMPI were 2.0 times more likely to report a back injury (P = 0.0001) than subjects with the lowest scores. The multivariate model, including job task enjoyment, MMPI Scale-3, and history of back treatment, revealed that subjects in the highest risk group had 3.3 times the number of reports in the lowest risk group. These findings emphasize the importance of adopting a broader approach to the multifaceted problem of back complaints in industry and help explain why past prevention efforts focusing on purely physical factors have been unsuccessful.

A Comparison of Physical Therapy, Chiropractic Manipulation, and Provision of an Educational Booklet for the Treatment of Patients with Low Back Pain

BACKGROUND AND METHODS There are few data on the relative effectiveness and costs of treatments for low back pain. We randomly assigned 321 adults with low back pain that persisted for seven days after a primary care visit to the McKenzie method of physical therapy, chiropractic manipulation, or a minimal intervention (provision of an educational booklet). Patients with sciatica were excluded. Physical therapy or chiropractic manipulation was provided for one month (the number of visits was determined by the practitioner but was limited to a maximum of nine); patients were followed for a total of two years. The bothersomeness of symptoms was measured on an 11-point scale, and the level of dysfunction was measured on the 24-point Roland Disability Scale. RESULTS After adjustment for base-line differences, the chiropractic group had less severe symptoms than the booklet group at four weeks (P=0.02), and there was a trend toward less severe symptoms in the physical therapy group (P=0.06). However, these differences were small and not significant after transformations of the data to adjust for their non-normal distribution. Differences in the extent of dysfunction among the groups were small and approached significance only at one year, with greater dysfunction in the booklet group than in the other two groups (P=0.05). For all outcomes, there were no significant differences between the physical-therapy and chiropractic groups and no significant differences among the groups in the numbers of days of reduced activity or missed work or in recurrences of back pain. About 75 percent of the subjects in the therapy groups rated their care as very good or excellent, as compared with about 30 percent of the subjects in the booklet group (P<0.001). Over a two-year period, the mean costs of care were

Determinants of Lumbar Disc Degeneration: A Study Relating Lifetime Exposures and Magnetic Resonance Imaging Findings in Identical Twins

437 for the physical-therapy group,

Lumbar disc degeneration: epidemiology and genetic influences.

429 for the chiropractic group, and

1991 volvo award in clinical sciences : smoking and lumbar intervertebral disc degeneration : an MRI study of identical twins

153 for the booklet group. CONCLUSIONS For patients with low back pain, the McKenzie method of physical therapy and chiropractic manipulation had similar effects and costs, and patients receiving these treatments had only marginally better outcomes than those receiving the minimal intervention of an educational booklet. Whether the limited benefits of these treatments are worth the additional costs is open to question.

Intragenic polymorphisms of the vitamin D receptor gene associated with intervertebral disc degeneration.

Study Design Retrospective cohort. Objectives To investigate the effects of lifetime exposure to commonly suspected risk factors on disc degeneration using magnetic resonance imaging, and to estimate the effects of these suspected risk factors relative to age and familial aggregation, reflecting genetic and shared environmental influences. Summary of Background Data Structural and biochemical changes associated with disc degeneration are suspected as the underlying conditions of many back-related symptoms. Little is known about the determinants of disc degeneration. Methods Based on lifetime discordance in suspected environmental risk factors for disc degeneration, 115 male identical twin pairs were selected. An indepth interview was conducted of occupational and leisure time physical loading, driving, and smoking. Disc degeneration was evaluated using observational and digital magnetic resonance imaging assessment methods. Results Heavier lifetime occupational and leisure physical loading was associated with greater disc degeneration in the upper lumbar levels (P = 0.055− 0.001), whereas sedentary work was associated with lesser degeneration (P = 0.006). These univariate associations did not reasch statistical significance in the lower lumbar region. In multivariate analyses of the upper lumbar levels, the mean job code explained 7% of the variability in observational disc degeneration scores; the addition of age explained 16%, and familial aggregation improved the model such that 77% of the variability was explained. In the lower lumbar levels, leisure time physical loading entered the multivariate model, explaining 2% of the variability. Adding age explained 9%, and familial aggregation raised the variability in disc degeneration scores explained to 43%. Conclusion The present study findings suggest that disc degeneration may be explained primarily by genetic influences and by unidentified factors, which may include complex, unpredictable interactions. The particular environmental factors studied, which have been among those most widely suspected of accelerating disc degeneration, had very modest effects.

The Long-term Effects of Physical Loading and Exercise Lifestyles on Back-related Symptoms, Disability, and Spinal Pathology Among Men

Study Design. A literature review. Objective. To synthesize the scientific literature on the prevalence of lumbar disc degeneration and factors associated with its occurrence, including genetic influences. Methods. A literature review was conducted of the prevalence of disc degeneration. Studies of the etiology of disc degeneration were summarized, with particular attention given to studies of genetic influences. Results and Conclusions. There are extreme variations in the reported prevalence of specific degenerative findings of the lumbar spine among studies, which cannot be explained entirely by age or other identifiable risk factors (e.g., prevalence figures for disc narrowing varied from 3% to 56%). It is likely that these variations are due, in great part, to inconsistencies in case definitions and measurements, which are impeding epidemiologic research on disc degeneration. Research conducted over the past decade has led to a dramatic shift in the understanding of disc degeneration and its etiology. Previously, heavy physical loading was the main suspected risk factor for disc degeneration. However, results of exposure-discordant monozygotic and classic twin studies suggest that physical loading specific to occupation and sport has a relatively minor role in disc degeneration, beyond that of upright postures and routine activities of daily living. Recent research indicates that heredity has a dominant role in disc degeneration, explaining 74% of the variance in adult populations studied to date. Since 1998, genetic influences have been confirmed by the identification of several gene forms associated with disc degeneration.

Lumbar disc degeneration: epidemiology and genetics.

The primary objective of this study was to determine whether disc degeneration, as assessed through magnetic resonance imaging, is greater in smokers than in nonsmokers. To control for the maximum number of potentially confounding variables, pairs of identical twins highly discordant for cigarette smoking were selected as study subjects. Data analyses revealed 18% greater mean disc degeneration scores in the lumbar spines of smokers as compared with nonsmokers. The effect was present across the entire lumbar spine, implicating a mechanism acting systemically. This investigation demonstrates the efficiency of using carefully selected controls in studying conditions of multifactorial etiology, such as disc degeneration.

Heritability of low back pain and the role of disc degeneration.

Study Design. A study in genetic epidemiology of disc degeneration, based on lifetime exposure data, findings on magnetic resonance imaging, and genotyping of intragenic markers. Objectives. To pursue the potential correlation between common allelic variations in the vitamin D receptor locus and degeneration of the intervertebral disc. Summary of Background Data. Familial aggregation has been observed in intervertebral disc degeneration, but the relative significance of the genetic component and shared environmental influences is unknown. The identification of relevant candidate genes associated with disc degeneration would specify a genetic component and increase our understanding of the etiopathogenesis of disc degeneration. Methods. From the population‐based Finnish Twin cohort, 85 pairs of male monozygotic twins were selected based on exposure to suspected risk factors for disc degeneration. Interview data were gathered on relevant lifetime exposures, and thoracic and lumbar disc degeneration was determined through quantitative and qualitative assessments of signal intensity on magnetic resonance imaging, and qualitative assessments of disc bulging and disc height narrowing. Possible associations were examined between disc degeneration measures and two polymorphisms of the coding region of the vitamin D receptor locus. Results. Two intragenic polymorphisms of the vitamin D receptor gene revealed an association with disc degeneration. Quantitatively assessed signal intensities of thoracic and lumbar (T6‐S1) discs were 12.9% worse in men with the TaqI tt genotype and 4.5% worse in men with the Tt genotype, compared with signal intensity in men with the TT genotype (age‐adjusted P = 0.003). A similar pattern was found between disc signal intensity and FokI genotypes; men with the ff and Ff genotypes had mean signal intensities that were 9.3% and 4.3% lower, respectively, than those in men with FF genotypes (age‐adjusted P = 0.006). The summary scores of qualitatively assessed signal intensity, bulging, and disc height were 4.0% and 6.9% worse in men with Ff and ff genotypes, respectively, when compared with those in men with the FF genotype (age‐adjusted P = 0.029). Conclusion. Specific vitamin D receptor alleles were associated with intervertebral disc degeneration as measured by T2‐weighted signal intensity, demonstrating for the first time the existence of genetic susceptibility to this progressive, age‐related degenerative process.

Associations between back pain history and lumbar MRI findings.

Study Design Historical cohort, including selected subgroups. Objectives To understand the long-term effects of exercise on back-related outcomes, back pain, sciatica, back-related hospitalizations, pensions, and magnetic resonance imaging findings were studied among former elite athletes. Summary of Background Data Exercise and sports participation have become increasingly popular, as have recommendations of exercises for back problems, but little is known about their long-term effects. Methods Questionnaires were returned by 937 former elite athletes and 620 control subjects (83% response rate). Identification codes allowed record linkage to hospital discharge and pension registers. Magnetic resonance images were obtained of selected subgroups with contrasting physical loading patterns. Results Odds ratios for back pain were lower among athletes than among control subjects, with significant differences in endurance, sprinting and game sports, and wrestling and boxing. No differences in the occurrence of sciatica or in back-related pensions and hospitalizations were seen. When comparing lumbar magnetic resonance images of 24 runners, 26 soccer players, 19 weight lifters, and 25 shooters, disc degeneration and bulging were most common among weight lifters; soccer players had similar changes in the L4-S1 discs. No significant differences were seen in the magnetic resonance images of runners and shooters. Conclusions Maximal weight lifting was associated with greater degeneration throughout the entire lumbar spine, and soccer with degeneration in the lower lumbar region. No signs of accelerated disc degeneration were found in competitive runners. However, back pain was less common among athletes than control subjects and there were no significant differences in hospitalizations or pensions. No benefits were shown for vigorous exercise compared with lighter exercise with respect to back findings.