To determine if agricultural work is related to radiological flattening of lumbar lordosis, and to identify the relationship between of back pain and flat back in selected Korean farmers.

Between June 2006 and July 2008, 414 farmers, 155 (37.4%) males and 259 (62.6%) females participated in this study. We collected data on hazardous agricultural work postures and other factors from interviews, surveys, and x-ray views of lateral lumbar. The operational definition of a flat back was below -1 SD of lordotic angle, with a normal distribution between L1 and S1 level. Logistic regression analysis was conducted to evaluate the relationship between flat back and hazardous working posture ratio, sex, the severity of back pain.

Mean lordotic angle was 42.9±15.7°. Flat back had a higher prevalence in the females (24.7%) than the males (5.8%). The odds ratio of flat back risk is 3.30 (95% CI: 1.46~7.46) in the females compared to the males, 1.31 (95% CI: 0.61~2.79), 4.11 (95% CI: 1.77~9.55) in the group of hazardous working posture ratio compared to the low risk group, 2.78 (95% CI: 1.27~6.07), 5.74 (95% CI: 2.27~14.49) in the group of L4-L5 disc space narrowing compared to normal group, 3.06 (95% CI: 1.27~7.31), 5.45 (95% CI: 1.70~17.46) in the group of lumbar spine compression fracture compared to no fracture. Odds ratio of severe back pain is 2.29 (95% CI: 1.12~4.72) in the group of flat back compared to normal group.

Hazardous agricultural working postures, such as 'low- lifting, pulling, pushing work and high- squatting posture work' are associated with flat back. Low back pain is significantly associated with flat back group in female farmers.