Prevalence and risk factors of low bone mineral density in Chinese patients with systemic sclerosis: a case-control study

Objective. To study the prevalence and risk factors of low BMD in patients with SSc. Methods. Consecutive patients with SSc and an equal number of age-and gender-matched healthy subjects were screened for BMD, fat and lean mass by DXA scan. BMD, body composition and osteoporosis risk factors were compared between patients and controls. Associated factors for low BMD in SSc patients were studied by linear regression. Results. A total of 84 patients with SSc were studied [89% women; age 49.4 (11.3) years; 21% diffuse subtype; disease duration 7.8 (6.4) years]. Except for significantly lower BMI (P = 0.001), fat mass (P = 0.02) and lean body mass (P = 0.006) observed in SSc patients, the prevalence of other osteoporosis risk factors was similar to controls. Fourteen (17%) and five (6%) SSc patients had low BMD expected for age (z-score <-2.0) at the lumbar spine and hip, respectively. BMD of the lumbar spine, hip, femoral neck and whole body was significantly lower in SSc patients than controls, adjusted for age, sex, menopause and BMI (P<0.05 in all; effect size 0.44-0.54). Linear regression revealed increasing age, menopause and low BMI were independently associated with low BMD at the spine or hip in SSc patients. However, BMD did not correlate with the severity of involvement of the skin and other systems. Conclusion. BMD of the spine and hip is significantly lower in patients with SSc than in healthy subjects, which is independent of age, sex, menopause, low BMI and altered body composition.