In a prospective cohort study of 537 male professional drivers, the occurrence of sciatic pain showed stronger associations with measures of internal lumbar load expressed in terms of daily compressive dose Sed (MPa) and risk factor R (non-dimensional) according to ISO/WD 2631-5 (2013), than with measures of daily vibration exposure calculated as either 8-h energy-equivalent frequency-weighted acceleration (ms-2 r.m.s.) or Vibration Dose Value (ms-1.75) according to the EU Directive on mechanical vibration (2002). Herniated lumbar disc, previous lumbar trauma, and physical work load were also powerful predictors of the occurrence of sciatic pain over time. Psychosocial work environment was poorly associated with sciatic pain. The boundary values of risk factor R for low and high probabilities of adverse health effects on the lumbar spine, as proposed by international standard ISO/WD 2631-5 (2013), tend to underestimate the health risk in professional drivers.
