Objectives Epidemiologic evidence supporting optimal seating is limited and inconsistent. This cross-sectional study was conducted to examine the association between seat inclination, use of lumbar support, and the prevalence of clinically significant low-back pain among taxi drivers.

Methods A digital inclinometer was used to measure inclinations of seat surfaces (θ_seat) and backrests (θ_back), and calculate the back-to-thigh angle (θ_back-thigh). Structured interviews were conducted to gather information on the use of lumbar support and the prevalence of low-back pain that had led to medical attention or absence from driving in the past month. A multiple logistic regression analysis was used to estimate the prevalence odds ratio (OR) with adjustment for age, body mass index, professional seniority, monthly driving hours, and the intensity of exposure to whole-body vibration.

Results Among 224 drivers, the mean θ_seat and θ_backrest were 14.5 (SD 9.6) and 95.1 (SD 2.7) degrees, respectively, resulting in θ_back-thigh of 80.6 (SD 9.3) degrees. Fifty-five percent used a lumbar support regularly, but 25% reportedly had significant low-back pain. The prevalence of low-back pain was 23% among those with θ_back-thigh 91 degrees. The adjusted OR comparing those with a θ_back-thigh of ≤91 degrees to those with a θ_back-thigh of >91 degrees was 5.11 [95% confidence interval (95% CI) 1.07~24.4]. For regularly using drivers versus those not using lumbar support, the prevalence of low-back pain was 18% versus 34%, with an adjusted OR of 0.33 (95% CI 0.16~0.68). Neither θ_seat nor θ_backrest alone was significantly associated with low-back pain.

Conclusions The epidemiologic observation of this study was consistent with the results of prior biomechanical studies on appropriate seat inclinations and the use of lumbar support. Prospective studies are needed to confirm the true beneficial effects of these seating parameters.

Key terms automobile driving; epidemiology; low-back pain; lumbar support; occupational exposure; seat inclination; sitting posture; taxi driver