Several studies suggest that bone mineral density (BMD) is reduced in rheumatoid arthritis (RA). However, it is unclear whether this relationship holds in a representative community-based typical RA population. We examined the relationship between BMD and RA in a representative US population-based sample from the Third National Health and Nutrition Examination Survey (NHANES III: 1988-1994).
We selected subjects over age 60 with RA from NHANES III using previously described methods. Femoral neck BMD (FN-BMD) measured by dual-energy x-ray absorptiometry was compared for the RA (n = 106) and non-RA cohorts (n = 4,277). Multivariable linear regression models included known risk factors for osteoporosis. Further adjusted analyses compared the BMD among subgroups of patients with RA, such as those taking methotrexate (MTX), those with positive rheumatoid factor (RF), and those with elevated C-reactive protein (CRP).
Patients with RA more frequently reported poor health, a history of falling, cognitive impairment, early menopause, a history of chronic obstructive lung disease, higher total calcium intake, and thiazide use than the non-RA subjects (all p < 0.05). Adjusted FN-BMD was similar between the patients with RA (0.71 g/cm2) and non-RA subjects (0.72 g/cm2; p = 0.5). Among patients with RA, reduced BMD tended to be seen with MTX use (0.60 g/cm2, p = 0.07), CRP above 1 mg/dl (0.66 g/cm2, p = 0.09), and positive RF in female patients (0.68 g/cm2, p = 0.056). However, none of these findings reached statistical significance.
Among a US population-based representative sample, FN-BMD was similar in RA and non-RA patients. Several characteristics of patients with RA may be associated with reduced BMD.