Abstract
It has been reported that some risk factors smoking, deduced or limited physical activity, lumber disc degeneration, and trunk muscle weakness associated with higher incidences of low back pain. However, not enough research has been to determine which risk factor is the most predictive for developing low back pain. A five-year prospective study was conducted to determine the strength of association between these possible risk factors in asymptomatic subjects. Method; Our study group consisted of 63 volumteers (33 male and 30 female) who denied LBP at the time and who said that they had never suffered LBP. Sports activity was assessed according to the definition of Japan Welfare Ministry: 2 points-more than 30 min. of any kind of sport activities, more than twice a week and for more than one year; 1 point-irregularlyengaged in sports activities; 0 point-no sports activities. A smoking index was determined multiplying the number of cigarettes smoked by the number of years a person smoked. The degree of disc degeneration was assessed by sagittal MRI on a five-point scale applied to each disc level (L2/3, L3/4 and L5/S) according to Gibson (change in the signal from nucleus pulposus) and Tate (degree of disc protrusion). Trunk muscle strength was measured isokinetically (60 deg/sec) using Trunk Extension/ Flexion units. The ratio of peak torque in extension to flexion was calculated as E/F ratio. They were then followed prospectively for 5 years to determine the incidence of LBP and compared the correlation coefficient of each risk factor by multiple regression analysis. Result; The incidence of LBP during the 5 years was 39% in males and 63% in females. For men, the correlation coefficients were -0.40 for EiF ratio, -0.35 for body weight, 0.31 for the degree of disc protrusion, 0.19 for signal change of disc, -0.18 for height, 0.15 for smoking index, -0.08 for ports activity, and 0.04 for age. For women -0.46 for E/F ratio, 0.39 for the degree of disc protrusion, 0.28 for height, 0.26 for smoking index, 0.17 for body weight, 0.16 for signal change of disc, 0.13 for age, and 0.01 for sports activity. Stepwise regression analysis revealed that the E/F ratio was the most predictive risk factor in both male and female ceses. Conclusion; According to our study, the imbalance of trunk muscle strength, is the most critical risk factor in the development of LBP in both men and women.
