Psoriatic Arthritis May Be a Risk Factor for Low BMD, But Association Not Genetically Determined

While patients with psoriatic arthritis (PsA) may be at increased risk for osteopenia and osteoporosis, this association is not causal but secondary to other factors, such as treatment with methotrexate or ciclosporin, according to study results published in Annals of the Rheumatic Diseases.

Previous studies have reported inconsistent findings of the association between psoriasis and PsA and osteoporosis and fractures. The objective of the current study was to investigate the association of psoriasis and PsA with bone mineral density (BMD), by a population-based observational study and a weighted Genetic Risk Score (wGRS).

Using the United Kingdom Biobank dataset, the researchers performed a cross-sectional study to examine the association between psoriasis or PsA and BMD, osteopenia, and osteoporosis. Furthermore, they used the wGRS method to estimate the effect of psoriasis/PsA single-nucleotide variations (formerly single-nucleotide polymorphisms) on estimated BMD and psoriasis. Potential confounders were categorized in 3 ways, including model 0 (age, height, weight, smoking, and drinking habits), model 1 (model 0 + regular physical activity), and model 2 (model 1 + medication treatments).

The data suggest an association between PsA with low estimated BMD in model 0 (β-coefficient=-0.014; P =.0006). This association became less significant after adjusting for regular physical exercise (β-coefficient=-0.013; P =.002), and disappeared when treatment with methotrexate or ciclosporin was included in the model (β-coefficient=-0.005; P =.28). Mediation analysis showed that 63% of the intermediary effect on estimated BMD was mediated by the medication treatment.

There was no association between psoriasis and estimated BMD, as psoriasis without arthritis was not a risk factor for low BMD and osteoporosis and the estimated BMD was not different in these patients compared with control participants. While the risk for osteopenia was increased in patients with PsA (odds ratio, 1.27; 95% CI, 1.09-1.47; P =.002), it was most likely secondary, as further investigation showed that the effect of PsA was partially intermediate by treatment with methotrexate or ciclosporin. The association between PsA and BMD, osteoporosis, or fracture was not genetically determined according to Mendelian randomization or the wGRS analysis.

“These results suggested that, in clinical practice, patients [with PsA] should be screened for osteopenia and osteoporosis and proper management should be provided to reduce the fracture risk, especially for those who received treatment with methotrexate or ciclosporin,” the researchers concluded.

Reference

Xia J, Xie SY, Liu KQ, et al. Systemic evaluation of the relationship between psoriasis, psoriatic arthritis and osteoporosis: observational and Mendelian randomisation study. Ann Rheum Dis. Published online July 31, 2020. doi:10.1136/annrheumdis-2020-217892