High incidence of clinical fragility fractures in postmenopausal women with rheumatoid arthritis. A case-control study

Application of two-sample Mendelian randomization method to assess the causal relationship between rheumatoid arthritis and osteoporotic fracture

Background

The association between rheumatoid arthritis (RA) and osteoporotic fracture has garnered considerable attention; however, the causal relationships between diseases remain uncertain. Therefore, this study employed Mendelian randomization (MR) analysis to investigate the causal effects of RA on osteoporotic fracture.

Methods

The summary data for RA and osteoporotic fracture were extracted from the genome-wide association studies (GWAS) catalog and the Finn Biobank database. The database provides information about diseased and health control subjects. We searched the database for the following conditions: RA, osteoporosis (OP), and osteoporotic fractures. Entries were published by investigating centers, which had established definitions and diagnostic criteria. We downloaded and processed the data to obtain the single-nucleotide polymorphisms (SNPs) strongly associated with RA, OP, and osteoporotic fracture. RA genetic associations were obtained from the GWAS catalog, including 1961 cases and 454,387 controls. The osteoporosis of the GWAS catalog involved 991 cases and 455,357 controls, and the data of the Finn Biobank involved 8,017 cases and 391,037 controls. Genetic associations for osteoporotic fracture were taken from the Finn Biobank of 1822 cases and 311,210 controls. Independent SNPs that are significantly associated with meeting the criteria of p < 5 × 10-8, r2 < 0.001, and kb = 10,000 were selected for MR analysis. The inverse variance-weighted (IVW) method along with other MR methods was employed for analysis, while sensitivity analyses were conducted to assess reliability and stability.

Results

The results provided strong evidence that RA was causally and positively associated with osteoporosis from the GWAS catalog (OR = 1.16590; 95% CI: 1.04067-1.30619; p = 0.00811) and the Finn Biobank database (OR = 1.07314; 95% CI: 1.03455-1.11317; p = 0.00016). Moreover, a positive causal relationship was detected between RA and osteoporotic fracture (OR = 1.10132; 95% CI: 1.00506-1.20680; p = 0.03863). The results were robust according to sensitivity tests.

Conclusion

This study showed positive causal relationships between RA and osteoporotic fracture. These results should be considered in further studies and public health measures on osteoporosis prevention strategies.

The Heterogeneity of Post-Menopausal Disease Risk: Could the Basis for Why Only Subsets of Females Are Affected Be Due to a Reversible Epigenetic Modification System Associated with Puberty, Menstrual Cycles, Pregnancy and Lactation, and, Ultimately, Menopause?

For much of human evolution, the average lifespan was <40 years, due in part to disease, infant mortality, predators, food insecurity, and, for females, complications of childbirth. Thus, for much of evolution, many females did not reach the age of menopause (45-50 years of age) and it is mainly in the past several hundred years that the lifespan has been extended to >75 years, primarily due to public health advances, medical interventions, antibiotics, and nutrition. Therefore, the underlying biological mechanisms responsible for disease risk following menopause must have evolved during the complex processes leading to Homo sapiens to serve functions in the pre-menopausal state. Furthermore, as a primary function for the survival of the species is effective reproduction, it is likely that most of the advantages of having such post-menopausal risks relate to reproduction and the ability to address environmental stresses. This opinion/perspective will be discussed in the context of how such post-menopausal risks could enhance reproduction, with improved survival of offspring, and perhaps why such risks are preserved. Not all post-menopausal females exhibit risk for this set of diseases, and those who do develop such diseases do not have all of the conditions. The diseases of the post-menopausal state do not operate as a unified complex, but as independent variables, with the potential for some overlap. The how and why there would be such heterogeneity if the risk factors serve essential functions during the reproductive years is also discussed and the concept of sets of reversible epigenetic changes associated with puberty, pregnancy, and lactation is offered to explain the observations regarding the distribution of post-menopausal conditions and their potential roles in reproduction. While the involvement of an epigenetic system with a dynamic "modification-demodification-remodification" paradigm contributing to disease risk is a hypothesis at this point, validation of it could lead to a better understanding of post-menopausal disease risk in the context of reproduction with commonalities may also lead to future improved interventions to control such risk after menopause.

Analysis of the Relationship between Rheumatoid Arthritis and Osteoporosis Based on Mendelian Randomization

BACKGROUND

As the global population ages, the World Health Organization has found a yearly increase in the incidence of rheumatoid arthritis and osteoporosis. This trend poses a challenge to public health and healthcare and calls for the implementation of more preventive and treatment measures to address these health issues.

OBJECTIVE

This study aims to investigate the causal relationship between rheumatoid arthritis (RA) and osteoporosis (OP) using the Mendelian randomization (MR) method.

METHODS

OP diagnosis was based on the gold standard of bone mineral density (BMD). Single nucleotide polymorphisms (SNPs) were identified from the genome-wide association research database formed by RA and BMD, with a parameter setting of P < 5×10-8, chain imbalance r2<0.01, and kb = 10,000. Five complementary MR methods, including inverse variance weighted (IVW), MR-Egger regression, weighted median, simple mode estimation based on mode, and weighted estimation based on mode, were used to evaluate the causal relationship between RA and OP/BMD using odds ratio (OR) values and 95% confidence intervals (CI). Sensitivity analyses were performed using heterogeneity tests, horizontal pleiotropy, and individual rejection tests.

RESULTS

A total of 78 instrumental variables were identified that were closely related to both RA and BMD in mixed populations, while 14 instrumental variables were identified in the European population and 38 instrumental variables were identified in the Asian population. Using IVW as the main analysis method, the MR analysis results of RA and BMD showed the following: mixed population OR = 0.96, 95%CI: 0.93-1.00; European population OR = 0.55, 95%CI: 0.27-1.12; and Asian population OR = 0.95, 95%CI: 0.90-1.01. Sensitivity analyses showed that the MR results were robust.

CONCLUSION

The study found insufficient evidence of a causal relationship between RA and OP/BMD, suggesting that RA may not have a direct effect on OP/BMD.

Whole-hand and regional bone mineral density involvement in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by symmetric polyarthritis that can lead to joint deformity, disability, and osteoporosis. We aimed to evaluate whole hand and regional BMD in RA patients compared to controls. In addition, we evaluated the BMD of dominant versus non-dominant hands in healthy subjects. We included adult female and male RA patients and control subjects matched by age, sex, and BMI. BMD (g/cm2) was measured by DXA in lumbar spine (LS), whole hand, and three regions of interest: carpus, metacarpal bones, and phalanges. Results: 44 control subjects (49.5±11.8 y) and 60 with RA (52.7±12.7 y) were included. Significant lower BMD in RA patients was found in LS (-8.7%), dominant whole hand (-9.5%), carpus, metacarpal bones, and phalanges, and non-dominant whole hand (-8.7%), metacarpal bones, and phalanges compared to controls. A significant positive correlation was found between LS and whole-hand BMD (dominant r=.63, non-dominant r=.67). Finally, the whole hand, metacarpal bones, and carpus BMD measurements were significantly higher in the dominant hand compared to the non-dominant hand without differences in the phalangeal ROI. In conclusion, hand BMD was significantly lower in RA patients compared to control subjects and there was a significant correlation with LS BMD. We demonstrated that BMD measurements of the whole-hand, and different ROI (carpus, metacarpal bones, and phalanges) by DXA would be an easily reproducible technique to evaluate bone loss. In addition, the whole hand, metacarpal bones and carpus BMD measurements were significantly higher in the dominant hand compared to the non-dominant hand without differences in the phalanges.