Potential Risk Factors of Persistent Low Back Pain Developing from Mild Low Back Pain in Urban Japanese Workers

<div><p>Study Design</p><p>Two-year, prospective cohort data from the Japan epidemiological research of occupation-related back pain study in urban settings were used for this analysis.</p><p>Objective</p><p>To examine the association between aggravated low back pain and psychosocial factors among Japanese workers with mild low back pain.</p><p>Summary of Background Data</p><p>Although psychosocial factors are strongly indicated as yellow flags of low back pain (LBP) leading to disability, the association between aggravated LBP and psychosocial factors has not been well assessed in Japanese workers.</p><p>Methods</p><p>At baseline, 5,310 participants responded to a self-administered questionnaire including questions about individual characteristics, ergonomic work demands, and work-related psychosocial factors (response rate: 86.5%), with 3,811 respondents completing the 1-year follow-up questionnaire. The target outcome was aggravation of mild LBP into persistent LBP during the follow-up period. Incidence was calculated for the participants with mild LBP during the past year at baseline. Logistic regression was used to explore risk factors associated with persistent LBP.</p><p>Results</p><p>Of 1,675 participants who had mild LBP during the preceding year, 43 (2.6%) developed persistent LBP during the follow-up year. Multivariate analyses adjusted for individual factors and an ergonomic factor found statistically significant or almost significant associations of the following psychosocial factors with persistent LBP: interpersonal stress at work [adjusted odds ratio (OR): 1.96 and 95% confidence interval (95%CI): 1.00–3.82], job satisfaction (OR: 2.34, 95%CI: 1.21–4.54), depression (OR: 1.92, 95%CI: 1.00–3.69), somatic symptoms (OR: 2.78, 95%CI: 1.44–5.40), support from supervisors (OR: 2.01, 95%CI: 1.05–3.85), previous sick-leave due to LBP (OR: 1.94, 95%CI: 0.98–3.86) and family history of LBP with disability (OR: 1.98, 95%CI: 1.04–3.78).</p><p>Conclusions</p><p>Psychosocial factors are important risk factors for persistent LBP in urban Japanese workers. It may be necessary to take psychosocial factors into account, along with physical work demands, to reduce LBP related disability.</p></div

Adjusted odds ratios of the baseline factors for persistent low back pain (LBP) with work disability; factors with crude odds ratio P values<0.1.

<p>OR: odds ratio, CI: confidence interval, LBP: low back pain</p>a<p>Adjusted for age, gender, obesity, smoking habits, and education.</p>b<p>Adjusted for age, gender, obesity, smoking habits, education, and manual handling of materials at work.</p>c<p>Bending, twisting, lifting, and pushing: ≥ half of the day was considered frequent.</p>d<p>Hours of desk work: longer than 6 hours per day was considered to be static posture.</p>e<p>Work-related stress factors assessed with the brief job stress questionnaire: not feeling stressed, feeling stressed: the 5 original responses were reclassified into “not feeling stressed”, where low, slightly low and moderate were combined, and “feeling stressed”, where slightly high and high were combined.</p

Flow diagram of study selection.

<p>Flow diagram of study selection.</p

Categories of psychometric tests.

<p>Categories of psychometric tests.</p

Calculation of proportional impairment ratio for objective tests by dose.

<p>a: Number of tests showing ‘impairment’ with the named antihistamine (AH). b: Number of tests showing ‘no impairment’ with the named AH. c: Number of tests showing ‘impairment’ with all other AHs. d: Number of tests showing ‘no impairment’ with all other AHs. L: Lower limit. U: Upper limit. The vertical dotted line in the figure of PIRs shows a value of 1.</p

Calculation of proportional impairment ratio for subjective tests for the second-generation antihistamines in Japan.

<p>a: Number of tests showing ‘impairment’ with the named antihistamine (AH). b: Number of tests showing ‘no impairment’ with the named AH. c: Number of tests showing ‘impairment’ with all other AHs. d: Number of tests showing ‘no impairment’ with all other AHs. L: Lower limit. U: Upper limit. The vertical dotted line in the figure of PIRs shows a value of 1.</p

Calculation of proportional impairment ratio for objective tests for the second-generation antihistamines in Japan.

<p>a: Number of tests showing ‘impairment’ with the named antihistamine (AH). b: Number of tests showing ‘no impairment’ with the named AH. c: Number of tests showing ‘impairment’ with all other AHs. d: Number of tests showing ‘no impairment’ with all other AHs. L: Lower limit. U: Upper limit. The vertical dotted line in the figure of PIRs shows a value of 1.</p

Number of test results showing impairment and no impairment for each AH by dose.

<p>Number of test results showing impairment and no impairment for each AH by dose.</p

Proportional impairment ratio calculation formula for an antihistamine.

<p>a: Number of tests showing ‘impairment’ with the named antihistamine (AH). b: Number of tests showing ‘no impairment’ with the named AH. c: Number of tests showing ‘impairment’ with all other AHs. d: Number of tests showing ‘no impairment’ with all other AHs.</p