Biologics control RA but do not stop bone loss: treat osteoporosis on its own terms

Design

Multicentre observational cohort, up to 5 years

Population

797 patients with active RA on b/tsDMARDs (152 also on osteoporosis treatment)

Primary outcome

Change in bone mineral density T score

Effect

No osteoporosis treatment: T score change -0.11 to -0.33 (P<0.001); 58% lost BMD overall

This multicentre Japanese cohort, published in April, followed 797 patients with active rheumatoid arthritis on biologic or targeted synthetic DMARDs for up to five years (median 3.1), measuring bone density. Of these, 152 were also on osteoporosis treatment and 645 were not.

Disease activity improved substantially in both groups, with the clinical disease activity index falling from about 25 to under 7. Yet T scores at the femoral neck and radius fell significantly in patients without osteoporosis treatment, while they did not change significantly in those on it. Overall, 58% lost bone density. Longer osteoporosis treatment was associated with gains; neither the duration of advanced therapy nor disease activity during follow-up predicted bone preservation.

This is observational, and patients chosen for osteoporosis treatment may differ. But the direction is consistent with the authors' earlier one-year data.

The practical message is that good disease control is not bone protection. Bone health in RA needs its own assessment and, where indicated, its own treatment, rather than being assumed to follow inflammatory remission.

• Assess fracture risk and bone density in RA patients on advanced therapy, even in remission.
• Do not assume that controlling inflammation will protect bone.
• Start osteoporosis treatment where fracture risk warrants it, alongside DMARDs.
• Minimise glucocorticoid exposure and review calcium and vitamin D intake.
• Repeat bone density measurement at appropriate intervals.

Why it matters

Osteoporosis treatment rates in RA are low, partly because clinicians assume remission protects bone.

Don't overread it

This observational cohort cannot prove that osteoporosis treatment caused the difference in bone density.

The statistics, in plain English

Mean T-score falls of 0.11 to 0.33 over about three years are modest for an individual but meaningful across a population at high fracture risk. The comparison with treated patients is not randomised.

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