Challenges of Measuring Self-Reported Exposure to Occupational Biomechanical Risk Factors Amongst People with Low Literacy Engaged in Manual Labour: Findings from a Cross-Cultural Adaptation and Psychometric Investigation in an African Population with Chronic Low Back Pain.

The cross-sectional design of the validity testing prevents causal conclusions; the negative associations between exposure and disability likely reflect the healthy worker effect rather than heavy work being protective. The questionnaire was interviewer-administered, which could introduce bias if interviewers inadvertently influenced responses, although training and fidelity checks were used. The study did not measure non-occupational biomechanical exposures (e.g., household chores), which are significant in this population and could confound self-perceptions of occupational load. The lack of data on work history (years of work, previous sick leave) makes it impossible to definitively confirm or rule out the healthy worker effect. Two specific items (operating powered hand tools and lifting 10–30 pounds) showed poor test-retest reliability, suggesting these activities may not be consistently performed or understood in this population.

The study was supported by the Schlumberger Foundation, Nature, and the Tertiary Education Trust Fund.

Do not interpret the finding that higher physical job exposure was associated with lower pain and disability as evidence that heavy manual labour is protective for low back pain. This result is likely an artefact of the study design and the 'healthy worker' effect, where those who are less disabled are the ones still able to perform heavy work.