Risk of Serious Infection With Low-dose Glucocorticoids in Patients With Rheumatoid Arthritis: An Instrumental Variable Analysis

Using Instrumental Variables to Measure Causation over Time in Cross-Lagged Panel Models

Cross-lagged panel models (CLPMs) are commonly used to estimate causal influences between two variables with repeated assessments. The lagged effects in a CLPM depend on the time interval between assessments, eventually becoming undetectable at longer intervals. To address this limitation, we incorporate instrumental variables (IVs) into the CLPM with two study waves and two variables. Doing so enables estimation of both the lagged (i.e., "distal") effects and the bidirectional cross-sectional (i.e., "proximal") effects at each wave. The distal effects reflect Granger-causal influences across time, which decay with increasing time intervals. The proximal effects capture causal influences that accrue over time and can help infer causality when the distal effects become undetectable at longer intervals. Significant proximal effects, with a negligible distal effect, would imply that the time interval is too long to estimate a lagged effect at that time interval using the standard CLPM. Through simulations and an empirical application, we demonstrate the impact of time intervals on causal inference in the CLPM and present modeling strategies to detect causal influences regardless of the time interval in a study. Furthermore, to motivate empirical applications of the proposed model, we highlight the utility and limitations of using genetic variables as IVs in large-scale panel studies.

Glucocorticoid use in rheumatoid arthritis patients and the onset of pneumonia: a systematic review and meta-analysis

CONTEXT

Rheumatoid arthritis (RA) is a systemic autoimmune disease that commonly affects joints. Although many treatment options exist, the most common, disease-modifying antirheumatic drugs (DMARDs), have been associated with pulmonary infections. These types of infections (specifically pneumonia) can be detrimental to RA patients. This leads providers to utilize other treatment modalities such as glucocorticoids (GCs). GCs are commonly utilized to treat RA; however, the role of GCs in the onset of pneumonia in RA patients is not fully understood.

OBJECTIVES

The goal of this study was to systematically review and statistically analyze pooled data documenting pneumonia as an adverse event in RA patients on DMARDs as a monotherapy vs RA patients on DMARDs and GCs as combination therapy utilizing the Population, Intervention, Comparison, and Outcomes (PICO) framework.

METHODS

On August 1, 2021, a search was conducted and completed on six databases: Embase, MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, International Pharmaceutical Abstracts (IPA), and ClinicalTrials.gov. A total of 12 researchers were involved with the search and screening of articles (K.E., P.R.; V.A., D.P.C.; C.B., D.C.; T.A., E.S.; S.H., L.B.; K.S., C.S.). Search terms were identified utilizing Medical Subject Headings (MeSH) and Emtree and included "glucocorticoids," "rheumatoid arthritis," "pneumonia," and "respiratory tract infections," Inclusion criteria included human subjects over the age of 18 with seropositive RA, on a combination of GC (prednisone, methylprednisolone, or prednisolone) with DMARD (methotrexate [MTX], hydroxychloroquine [HCQ], or sulfasalazine [SSZ]) and developed pneumonia of bacterial, viral, or fungal origin. The control groups were on a DMARD monotherapy regimen. Articles were excluded if they were not in English, had less than 20 participants, were case reports or literature reviews, included animal subjects, and did not adhere to the established PICO framework. Five teams of two researchers individually sorted through abstracts of articles based on the inclusion and exclusion criteria. The same teams individually sorted through full-text articles of selected abstracts based on the same criteria. Conflicts between each team were resolved by a separate researcher. Odds ratios were utilized to quantify the effect sizes of combined studies from a random effects model. Chi-square tests and I2 statistics were utilized to analyze heterogeneity.

RESULTS

A total of 3360 articles were identified from all databases, and 416 duplicate articles were removed. Thus, a total of 2944 articles abstracts were screened, of which 2819 articles either did not meet the inclusion criteria or did meet the exclusion criteria. A total of 125 articles were retrieved and assessed for full-text eligibility, of which only three observational articles were included for meta-analysis. Statistical results revealed that patients treated with DMARDs monotherapy are 95% (95% CI: 0.65-0.99) less likely to develop pneumonia compared to patients treated with a DMARD and GCs (p=0.002).

CONCLUSIONS

Our data suggest that RA patients have a higher probability of developing pneumonia on combination therapy with GCs, compared to monotherapy with DMARDs. To our knowledge, our findings are the first to systematically review and statistically evaluate the relationship between the use of GCs and show an increased chance of developing pneumonia.

Respiratory tract infections and risk factors for infection in a cohort of 330 patients with axial spondyloarthritis or psoriatic arthritis

Respiratory tract infections (RTIs) are the most common infections in patients with rheumatic diseases under immunosuppressive treatment and may contribute to morbidity and mortality as well as increased healthcare costs. However, to date only limited data on infection risk in spondyloarthritis (SpA) patients are available. In this study we assessed the occurrence of respiratory tract infections in a monocentric real-world cohort consisting of 330 patients (168 psoriatic arthritis and 162 axial spondyloarthritis patients) and determined factors associated with increased infection risk. Out of 330 SpA patients, 89.3% had suffered from ≥ 1 upper respiratory tract infection (URTI) and 31.1% from ≥ 1 lower respiratory tract infection (LRTI) within the last two years. The most common URTIs were rhinitis and laryngitis/pharyngitis with 87.3% and 36.1%, respectively. Bronchitis constituted the most common LRTI, reported in 29.7% of patients. In a multivariate binomial logistic regression model occurrence of LRTI was associated with chronic lung disease (OR 17.44, p=0.006), glucocorticoid therapy (OR 9.24, p=0.012), previous history of severe airway infections (OR 6.82, p=0.013), and number of previous biological therapies (OR 1.72, p=0.017), whereas HLA B27 positivity was negatively associated (OR 0.29, p=0.025). Female patients reported significantly more LRTIs than male patients (p=0.006) and had a higher rate of antibiotic therapy (p=0.009). There were no significant differences between axSpA and PsA patients regarding infection frequency or antibiotic use. 45.4% of patients had required antibiotics for respiratory tract infections. Antibiotic therapy was associated with smoking (OR 3.40, p=0.008), biological therapy (OR 3.38, p=0.004), sleep quality (OR 1.13, p<0.001) and age (OR 0.96, p=0.030). Hypogammaglobulinemia (IgG<7g/l) was rare (3.4%) in this SpA cohort despite continuous immunomodulatory treatment. Awareness of these risk factors will assist physicians to identify patients with an increased infection risk, who will benefit from additional preventive measures, such as vaccination and smoking cessation or adjustment of DMARD therapy.

Self-reported and genetically predicted effects of coffee intake on rheumatoid arthritis: Epidemiological studies and Mendelian randomization analysis

Background and aims

Causal research concerning coffee intake and rheumatoid arthritis (RA) risk is controversial. The objective of this study was to further explore the causal relationship between coffee intake and RA risk.

Methods

The 4,310 participants from NHANES 2003–2006 were included in an epidemiological study to assess the association between coffee intake and RA by weighted multivariate logistic regression. The inverse variance weighted (IVW) method of two-sample Mendelian randomization (MR), employing genetic data from UK Biobank (428,860 cases) of coffee intake and MR-Base platform (14,361 cases and 43,923 controls) of RA, was performed to estimate the causal relationship between coffee intake and RA.

Results

Weighted multivariate logistic regression suggested no significant correlation between coffee intake and RA. Compared to the no-coffee group, the odds ratio for RA in the <1, 1–3, ≥4 cups/day group were 1.297, 1.378, and 1.125 (P = 0.204, 0.098, and 0.698, respectively). In the IVW of MR analysis, there was no causal relationship between coffee intake and RA (OR = 1.47, P = 0.218).

Conclusion

Our study did not support a causal association between coffee intake and RA risk. However, it is necessary to consider valid information on coffee intake, including brewing method, type of coffee, and quantity, in further analysis of coffee intake and RA.