Objective Plasma C reactive protein (CRP) is a marker of inflammation, and increased plasma CRP is reported in many diseases, including cardiovascular disease, diabetes, metabolic syndrome, arthritis and malignancies. The aim of the study was to evaluate the association between plasma CRP levels and cardiovascular disease, metabolic syndrome, malignancies and other comorbidities. Design A retrospective, cross-sectional survey study. Setting Large population survey in Korea. Methods A total of 5887 (weighted n=40 251 868) participants aged 19 years or older from the 2016 Korea National Health and Nutrition Examination Survey were included for analysis. Weighted prevalence and OR of comorbidities were analysed according to the continuous variable of log plasma high-sensitivity CRP levels. Results The mean age was 46.7±0.37 years and the median plasma CRP was 0.58 mg/L (IQR 0.36–1.09). The mean plasma CRP levels were higher in participants with cardiovascular diseases and cardiovascular risk factors, osteoarthritis, rheumatoid arthritis, pulmonary tuberculosis, and several cancers, including gastric, colon, breast and cervix, than in the general population. In the multivariable analysis, plasma CRP concentration was associated with increased prevalence of hypertriglyceridaemia (OR 1.157, 95% CI 1.040 to 1.287, p=0.007), diabetes (OR 1.204, 95% CI 1.058 to 1.371, p=0.005) and metabolic syndrome (OR 1.228, 95% CI 1.112 to 1.357, p<0.001) after adjustment for socioeconomic and lifestyle characteristics. There was no significant association between plasma CRP level and cancers. Conclusion Plasma CRP was associated with an increased risk of dyslipidaemia, diabetes and metabolic syndrome in the general population.

Hyperuricemia is an emerging potential biomarker for metabolic syndrome (MetS) and its complications. This study aimed to investigate the risk factors of hyperuricemia, particularly, the association of hyperuricemia with MetS and general obesity according to sex. We performed multivariate logistic regression analyses using the 2016 Korean National Health and Nutrition Examination Survey data. Hyperuricemia was defined by a serum uric acid level ≥7.0 mg/dL for men and ≥6.0 mg/dL for women. General obesity was based on a body mass index (BMI) ≥25 kg/m². Among a total of 5591 Korean adult participants, 685 (12.3%) individuals had hyperuricemia. Hyperuricemia was significantly associated with MetS in men (odds ratio (OR): 2.38, 95% CI: 1.84–3.08) and in women (OR: 4.15, 95% CI: 2.75–6.28) after adjustments. General obesity was also independently related to hyperuricemia in both sexes (OR: 2.17, 95% CI: 1.76–2.68 in men, OR: 3.80, 95% CI: 2.82–5.12 in women). In subgroup analyses, the presence of concomitant MetS and general obesity posed a strikingly higher risk for hyperuricemia among women (OR: 7.24, 95% CI: 4.56–11.50) when compared to men (OR: 2.90, 95% CI: 2.12–3.96). More attention should be paid to the increased risk of hyperuricemia for females with both MetS and general obesity.

Background: Previous studies have shown that the incidence and risk factors of gout differs according to sex. However, little research has been done on the association between reproductive factors and gout. We conducted an analysis of a large nationwide population-based cohort of postmenopausal women to determine whether there is an association between reproductive factors and the incidence of gout. Methods: A total of 1,076,378 postmenopausal women aged 40–69 years who participated in national health screenings in 2009 were included in the study. The outcome was the occurrence of incident gout, which was defined using the ICD-10 code of gout (M10) in the claim database. Cox proportional hazard models were used for the analyses and stratified analyses according to body mass index (BMI) and the presence/absence of chronic kidney disease (CKD) were performed. Results: The mean follow-up duration was 8.1 years, and incident cases of gout were 64,052 (incidence rate 7.31 per 1000 person-years). Later menarche, earlier menopause, and a shorter reproductive span were associated with a high risk of gout. No association between parity and gout incidence was observed. Use of oral contraceptives (OC) and hormone replacement therapy (HRT) were associated with an increased risk of gout. The association between reproductive factors and gout was not statistical significant in the high BMI group. The effects of OC and HRT usage on gout were not significant in the CKD group. Conclusion: Shorter exposure to endogenous estrogen was associated with a high risk of gout. Conversely, exposure to exogenous estrogen such as OC and HRT was associated with an increased risk of gout.

Importance: Although it has been postulated that chronic inflammation caused by rheumatoid arthritis (RA) contributes to the development of Parkinson disease (PD), the association between these 2 conditions has yet to be determined.Objective: To evaluate the association between RA and subsequent PD risk.Design, Setting, and Participants: This retrospective cohort study used the Korean National Health Insurance Service database to collect population-based, nationally representative data on patients with RA enrolled from 2010 to 2017 and followed up until 2019 (median follow-up, 4.3 [IQR, 2.6-6.4] years after a 1-year lag). A total of 119 788 patients who were first diagnosed with RA (83 064 with seropositive RA [SPRA], 36 724 with seronegative RA [SNRA]) were identified during the study period and included those who underwent a national health checkup within 2 years before the RA diagnosis date (64 457 patients). After applying exclusion criteria (eg, age <40 years, other rheumatic diseases, previous PD), 54 680 patients (39 010 with SPRA, 15 670 with SNRA) were included. A 1:5 age- and sex-matched control group of patients without RA was also included for a total control population of 273 400.Exposures: Rheumatoid arthritis as defined using International Classification of Diseases, Tenth Revision codes M05 for SPRA and M06 (except M06.1 and M06.4) for SNRA; prescription of any disease-modifying antirheumatic drug; and enrollment in the Korean Rare and Intractable Diseases program.Main Outcomes and Measures: The main outcome was newly diagnosed PD. Data were analyzed from May 10 through August 1, 2022, using Cox proportional hazards regression analyses.Results: From the 328 080 individuals analyzed (mean [SD] age, 58.6 [10.1] years; 74.9% female and 25.1% male), 1093 developed PD (803 controls and 290 with RA). Participants with RA had a 1.74-fold higher risk of PD vs controls (95% CI, 1.52-1.99). An increased risk of PD was found in patients with SPRA (adjusted hazard ratio [aHR], 1.95; 95% CI, 1.68-2.26) but not in patients with SNRA (aHR, 1.20; 95% CI, 0.91-1.57). Compared with the SNRA group, those with SPRA had a higher risk of PD (aHR, 1.61; 95% CI, 1.20-2.16). There was no significant interaction between covariates on risk of PD.Conclusions and Relevance: In this study, RA was associated with an increased risk of PD, and seropositivity of RA conferred an augmented risk of PD. The findings suggest that physicians should be aware of the elevated risk of PD in patients with RA and promptly refer patients to a neurologist at onset of early motor symptoms of PD without synovitis.

Importance: Depression is among the most common comorbidities in rheumatoid arthritis (RA). There is a lack of data regarding the association of RA seropositivity and biologic agents with depression risk among individuals with RA.Objective: To investigate the risk of depression following RA diagnosis among patients in South Korea.Design, Setting, and Participants: This retrospective cohort study included 38 487 patients with RA and a comparison group of 192 435 individuals matched 1:5 for age, sex, and index date. Data were from the Korean National Health Insurance Service database. Participants were enrolled from 2010 to 2017 and were followed up until 2019. Participants who had previously been diagnosed with depression or were diagnosed with depression within 1 year after the index date were excluded. Statistical analysis was performed in May 2023.Exposures: Seropositive RA (SPRA) was defined with the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes M05 and enrollment in the Korean Rare and Intractable Diseases program. Seronegative RA (SNRA) was defined with ICD-10 codes M06 (excluding M06.1 and M06.4) and a prescription of any disease-modifying antirheumatic drugs (DMARDs) for 270 days or more.Main Outcomes and Measures: Newly diagnosed depression (ICD-10 codes F32 or F33).Results: The mean (SD) age of the total study population was 54.6 (12.1) years, and 163 926 individuals (71.0%) were female. During a median (IQR) follow-up of 4.1 (2.4-6.2) years, 27 063 participants (20 641 controls and 6422 with RA) developed depression. Participants with RA had a 1.66-fold higher risk of depression compared with controls (adjusted hazard ratio [aHR], 1.66 [95% CI, 1.61-1.71]). The SPRA group (aHR, 1.64 [95% CI, 1.58-1.69]) and the SNRA group (aHR, 1.73 [95% CI, 1.65-1.81]) were associated with an increased risk of depression compared with controls. Patients with RA who used biologic or targeted synthetic DMARDs (aHR, 1.33 [95% CI, 1.20-1.47]) had a lower risk of depression compared with patients with RA who did not use these medications (aHR, 1.69 [95% CI, 1.64-1.74]).Conclusions and Relevance: This nationwide cohort study found that both SPRA and SNRA were associated with a significantly higher risk of depression. These results suggest the importance of early screening and intervention for mental health in patients with RA.