POPULATION-BASED STUDY OF SPINAL ANATOMY, LOAD-CARRYING PRACTICES, AND CHRONIC BACK DISORDERS IN INFORMAL WORKERS: STUDY OF SELECTED NIGERIAN CITIES

Abstract

Chronic back disorders are a leading cause of disability among informal workers in low- and middle-income countries, yet population-based evidence linking spinal anatomy to occupational load-carrying practices remains limited in Nigeria. This study examined the relationship between vertebral structure, habitual load carrying, and chronic back disorders among 1,200 informal workers across Lagos, Onitsha/Aba, and Kano. Participants included traders, farmers, and manual laborers aged 18–60 years who routinely carried loads for at least three years. Data collection combined structured questionnaires, direct observation of load-carrying practices, and spinal assessments using digital radiography and ultrasound imaging. Biomechanical stress scores were calculated based on load weight, duration, and posture, while chronic back disorders were assessed through self-reported pain scales and clinical examinations. Results indicated that 50.4% of participants reported chronic back disorders, with highest prevalence among manual laborers (60%) and farmers (51.4%). Head-loading practices, most common among traders, produced the highest biomechanical stress scores (7.8 ± 1.2) and were significantly associated with increased risk of chronic back disorders (OR=1.92; 95% CI: 1.48–2.49; p<0.001). Imaging revealed reduced lumbar disc thickness and increased paraspinal muscle thickness in participants with higher biomechanical stress, suggesting cumulative structural adaptations to repetitive loading. Age and duration in occupation moderated these associations, highlighting the impact of long-term exposure. The findings underscore the anatomical basis of occupational musculoskeletal risk in informal work settings and demonstrate the need for targeted interventions. Recommendations include ergonomic education, community-based occupational health screening, infrastructure support to reduce manual load carrying, and public health campaigns tailored to informal workers. Integrating spinal anatomy assessments with occupational exposure provides critical insights for prevention, early diagnosis, and policy strategies aimed at mitigating chronic back disorders in Nigeria’s informal workforce.