Anticholinergic burden and bone health in rheumatoid arthritis

Rheumatoid arthritis is associated with osteoporosis and falls. While anticholinergic burden increases fracture risk in older adults, its contribution to bone health in rheumatoid arthritis is unclear. The aim of this study was to determine if anticholinergic burden is an independent risk factor for osteoporosis and fracture in rheumatoid arthritis.

This retrospective cohort study included 120 adults with rheumatoid arthritis. Cumulative anticholinergic burden was quantified using eight validated scales (anticholinergic burden, Anticholinergic Risk Scale, Anticholinergic Drug Scale, Clinician-rated Anticholinergic Scale, Anticholinergic Activity Scale, Anticholinergic Effect on Cognition Scale, Anticholinergic Loading Scale, and CRIDECO). Outcomes included lumbar spine and hip bone mineral density, Fracture Risk Assessment Tool 10-year fracture probabilities, and World Health Organization-defined osteoporosis. Fracture Risk Assessment Tool major and L1-L4 T-score models included age, body mass index, rheumatoid arthritis duration, anticholinergic burden Calc Score, and Anticholinergic Drug Scale Score, whereas the binary osteoporosis model included age, body mass index, comorbidity count, anticholinergic burden Calc Score, and Anticholinergic Drug Scale Score.

In unadjusted analyses, only Clinician-rated Anticholinergic Scale ≥1 was associated with osteoporosis (p=0.010), whereas the other thresholdbased scales were not. After adjustment for the covariates specified in each model, neither anticholinergic burden Calc Score nor Anticholinergic Drug Scale Score independently predicted Fracture Risk Assessment Tool major probability (p=0.415 and p=0.189), L1-L4 T-score (p=0.436 and p=0.291), or binary osteoporosis status (p=0.849 and p=0.653). Age remained the only independent predictor in the osteoporosis model (OR 1.083; 95%CI 1.019-1.151; p=0.010), whereas older age and lower body mass index predicted higher Fracture Risk Assessment Tool major probability.

In rheumatoid arthritis, the apparent relationship between anticholinergic burden and osteoporosis is largely explained by age, body composition, and comorbidity-related prescribing. Although anticholinergic burden was not an independent fracture risk factor after adjustment, higher anticholinergic burden may still reflect greater prescribing complexity and comorbidity burden in rheumatoid arthritis.