Background In the general population associations between low bone mineral density (BMD) and severity of carotid atherosclerosis as well as cardiovascular disease (CVD) have been reported.
Objectives We aimed here to examine the relationship between bone mass and carotid measurements in patients with systemic lupus erythematosus (SLE) and controls.
Methods In all, 111 patients with SLE and 111 age- and sex-matched controls were enrolled, mean age 48.7 (12.9) years, 89% were women (51% postmenopausal). Carotid intima media thickness (cIMT), carotid plaque and echogenicity were determined by B-mode ultrasound and BMD by dual-energy X-ray absorptiometry. Low BMD was defined as a T-score less than -1.0 SD.
Results Distribution of women in post-menopause, BMI, smoking habits, hypercholesterolemia and diabetes was similar between the groups. Patients had hypertension and history of CVD more often than controls. The majority of the patients had a long-standing disease (median 9.0 (5-17) years), low disease activity and severity. 60% of the patients were receiving oral prednisolone. Two-thirds of the patients and about one tenth of the controls were prescribed medication for osteoporosis. Compared with controls, patients had lower mean BMD measurements in total hip and femoral neck. Mean cIMT did not differ between the groups, but carotid plaque was more prevalent in patients.
BMD and cIMT were inversely associated both in patients and controls. The patients, but not the controls, with carotid plaque had higher cIMT at low BMD than at normal BMD, p=0.010. Logistic regression indicated more than doubled odds ratio (OR) of carotid plaque in patient than in controls in relation to all BMD measurements. For low BMD at hip, increased OR for echolucent plaque was shown for patients compared with controls, adjusted OR 2.19 (95%CI 1.05-4.55), p=0.036. Across all BMD measures, approximately 4-fold higher ORs for echogenic plaque were also found for patients compared with controls.
In the patients, significant impact of age, BMI, smoking, systolic blood pressure, blood lipids, diabetes mellitus, impaired renal function, low levels of complement C3 and C4, history of nephritis, SLICC and ever use of antimalarial was found for the association between cIMT measures and BMD. Multivariate regression analysis showed that low C4 was an independent contributor to the association between total BMD and the upper cIMT tertile, estimated OR of 3.2 (1.03-10.01), and also bilateral carotid plaque, OR of 4.8 (1.03-22.66). BMD, low C4, age, blood lipids and history of CVD together explained about 85% of the variance in cIMT measurements and presence of bilateral carotid plaque.
Conclusions Inverse association between BMD and carotid measurements was found both in SLE-patients and controls. SLE-patients may suffer higher burden of subclinical atherosclerotic disease, such as presence of both echolucent and echogenic plaque, than controls with the same bone mineral status. Disease factors appear to contribute to the enhanced association between low bone mass and carotid atherosclerosis in SLE-patients.
Disclosure of Interest None declared