Background To study the effect of osteoporosis on MACEs in a longitudinal cohort of patients with SLE.

Methods Patients who fulfilled ≥4 ACR criteria for SLE and had a DEXA scan performed were followed longitudinally. The incidence of MACEs documented by imaging studies was evaluated. Osteoporosis/fracture at baseline was defined as a T score of <-2.5 or Z score <-2.0 at the hip/femoral neck/spine, or old fragility fractures. The effect of osteoporosis on incident MACEs was studied by Cox regression, adjusted for confounders.

Results 383 SLE patients were studied (age 40.5±13 years; 94% women). Osteoporosis/fractures was present in 113 patients at baseline. Over 153±41 months, 44 MACEs (acute coronary syndrome [n=19]; ischemic stroke [n=19]; peripheral vascular disease with digital gangrene [n=6]) developed in 42 patients. The incidence of MACEs was significantly higher in patients with osteoporosis/fracture than those without (1.59 vs 0.63/100 patient-years; p=0.001). The cumulative risk of MACEs by KM plot was significantly higher in the osteoporosis than non-osteoporosis groups (p=0.002). Cox regression revealed osteoporosis/fracture was an independent risk factor for MACEs after adjustment for age, sex, vascular risk factors, past MACE, aPL antibodies, and the use of immunosuppressive drugs, aspirin/warfarin, statins, vitamin D and bisphosphonates (HR 2.41[1.25–4.67];p=0.009). 62(16%) patients succumbed and osteoporosis/fracture at baseline was associated with vascular mortality (HR 11.1[1.02–120]; p=0.048) but not with all-cause mortality after adjustment for the same confounders.

Conclusions Osteoporosis increases the risk of MACEs and vascular mortality in patients with SLE, which is not accounted by traditional vascular risk factors.