Background: Loss of muscle mass and central obesity progress with aging, but the effect of muscle loss on chronic low back pain has not been precisely evaluated.
Methods: Three hundred thirty Japanese persons aged 45 to 69 years, with a complaint of low back pain for longer than 3 months (n = 203) and age- and sex-matched healthy control subjects (n = 127), were enrolled in this study. Participants with chronic low back pain were classified into the following groups: (1) women with a positive straight leg raise test result, (2) women with a negative straight leg raise test result, (3) men with a positive straight leg raise test result, and (4) men with a negative straight leg raise test result. Controls were classified by sex into a female and a male group. Anthropometric data, consisting of body mass index, percentage body fat, waist-hip ratio, and lean body mass of the upper extremities, trunk, and lower extremities divided by body weight, were measured in participants with low back pain, and the results were compared with those of controls.
Results: The waist-hip ratio in women with a negative straight leg raise test result was significantly higher than those in the female control group (P<.001) and in the women with a positive straight leg raise test result (P =.04). The lean body mass of the trunk and lower extremities divided by body weight of women with a negative straight leg raise test result was significantly lower than that of female controls (P =.03 for the trunk and P<.001 for the lower extremities). However, no significant differences were detected between the female negative straight leg raise test result group and the female control group for lean body mass of the upper extremities divided by body weight or body mass index. There were no significant differences in anthropometric data between the male test and control groups or between the female positive straight leg raise test result group and the female control group.
Conclusion: Trunk and lower extremity loss of muscle mass and central obesity may be risk factors for chronic low back pain without a positive straight leg raise test result in women aged 45 to 69 years. Arch Intern Med. 2000;160:3265-3269.