Familial autoimmunity in patients with idiopathic inflammatory myopathies

BACKGROUND

Familial associations can be indicators of shared genetic susceptibility between two diseases. Previous data on familial autoimmunity in patients with idiopathic inflammatory myopathies (IIM) are scarce and inconsistent.

OBJECTIVES

To investigate which autoimmune diseases (ADs) may share genetic susceptibility with IIM, we examined the familial associations between IIM and different ADs.

METHODS

In this Swedish population-based family study, we assembled 7615 first-degree relatives (FDRs) of 1620 patients with IIM and 37,309 relatives of 7797 matched individuals without IIM. Via register linkages, we ascertained rheumatoid arthritis, other rheumatic inflammatory diseases (RIDs), multiple sclerosis, inflammatory bowel diseases (IBD), type 1 diabetes mellitus, autoimmune thyroid diseases (AITD), coeliac disease (CeD) and myasthenia gravis among the FDRs. We estimated the familial association between IIM and each AD using conditional logistic regression and performed subgroup analyses by kinship.

RESULTS

Patients with IIM had significantly higher odds of having ≥1 FDR affected by other RIDs (adjusted odds ratio [aOR] = 1.40, 95% confidence interval [CI] 1.11-1.78) and greater odds of having ≥2 FDRs affected by CeD (aOR = 3.57, 95% CI 1.28-9.92) compared to the individuals without IIM. In the analyses of any FDR pairs, we observed familial associations for other RIDs (aOR = 1.34, 95% CI 1.14-1.56), IBD (aOR = 1.20, 95% CI 1.02-1.41), AITD (aOR = 1.10, 95% CI 1.02-1.19) and CeD (aOR = 1.37, 95% CI 1.08-1.74) while associations for other ADs were not statistically significant.

CONCLUSION

The observed familial associations may suggest that IIM shares genetic susceptibility with various ADs, information that may be useful for clinical counselling and guiding future genetic studies of IIM.

Risk of diabetes mellitus associated with disease-modifying antirheumatic drugs and statins in rheumatoid arthritis

OBJECTIVE

To investigate the rate of incident diabetes mellitus (DM) in patients with rheumatoid arthritis (RA) and the impact of disease-modifying antirheumatic drug (DMARD) and statin treatments.

METHODS

We studied patients with RA and ≥1 year participation in the National Data Bank for Rheumatic Diseases without baseline DM from 2000 through 2014. DM was determined by self-report or initiating DM medication. DMARDs were categorised into four mutually exclusive groups: (1) methotrexate monotherapy (reference); (2) any abatacept with or without synthetic DMARDs (3) any other DMARDs with methotrexate; (4) all other DMARDs without methotrexate; along with separate statin, glucocorticoid and hydroxychloroquine (yes/no) variables. Time-varying Cox proportional hazard models were used to adjust for age, sex, socioeconomic status, comorbidities, body mass index and RA severity measures.

RESULTS

During a median (IQR) 4.6 (2.5-8.8) years of follow-up in 13 669 patients with RA, 1139 incident DM cases were observed. The standardised incidence ratio (95% CI) of DM in patients with RA (1.37, (1.29 to 1.45)) was increased compared with US adult population. Adjusted HR (95% CI) for DM were 0.67 (0.57 to 0.80) for hydroxychloroquine, 0.52 (0.31 to 0.89) for abatacept (compared with methotrexate monotherapy), 1.31 (1.15 to 1.49) for glucocorticoids and 1.56 (1.36 to 1.78) for statins. Other synthetic/biological DMARDs were not associated with any risk change. Concomitant use of glucocorticoids did not alter DM risk reduction with hydroxychloroquine (HR 0.69 (0.51 to 0.93)).

CONCLUSIONS

In RA, incidence of DM is increased. Hydroxychloroquine and abatacept were associated with decreased risk of DM, and glucocorticoids and statins with increased risk.

Risk of venous thromboembolism in patients with rheumatoid arthritis and association with disease duration and hospitalization

CONTEXT

Recent reports suggest that rheumatoid arthritis (RA) may be a risk factor for venous thromboembolism (VTE), particularly in conjunction with hospitalization. Using hospitalization data to identify RA and VTE may identify patients when they are at elevated risk for other reasons, obscuring the incompletely understood underlying association between RA and VTE and leading to inappropriate institution or timing of interventions.

OBJECTIVE

To estimate risks for VTE in patients with RA, including the relation of these risks to disease duration and hospitalization.

DESIGN, SETTING, AND PATIENTS

Prospective, population-based cohort study of 1 prevalent RA cohort (n = 37,856), 1 incident RA cohort (n = 7904), and matched general population comparison cohorts, all from Sweden, with follow-up from 1997 through 2010.

MAIN OUTCOME MEASURE

First-time VTE.

RESULTS

Patients with prevalent RA were at greater risk of VTE than the general population (rate, 5.9 [95% CI, 5.1-6.6] vs 2.8 [95% CI, 2.6-3.1] per 1000 person-years (adjusted hazard ratio [HR], 2.0 [95% CI, 1.9-2.2]; P < .001). By the time of RA symptom onset, there was no statistically significant association between a history of VTE and RA (odds ratio, 1.2 [95% CI, 1.0-1.4]; P = .08; 150 events in the RA cohort vs 587 in the comparison cohort). Counting from RA diagnosis, an increased rate in the RA cohort vs the comparison cohort (3.8 [95% CI, 2.5-5.2] vs 2.4 [95% CI, 1.9-2.9] per 1000 person-years; HR, 1.6 [95% CI, 1.1-2.5]; P = .02) was detected within the first year and did not increase further during the first decade. Although rates for VTE following hospitalization were higher, the 1-year rate of VTE per 1000 person-years was not higher in the RA cohort than in the comparison cohort after hospital discharge (11.8 [95% CI, 8.6-15.1] vs 13.1 [11.3-14.8]; HR, 1.0 [95% CI, 0.7-1.4]; P = .90). The rates of VTE increased with age but were largely similar across sex and rheumatoid factor status, as were the HRs for VTE across age, sex, and rheumatoid factor status.

CONCLUSIONS

Compared with the general population, Swedish patients with RA had an elevated risk for VTE that was stable over the first 10 years after diagnosis. Although hospitalization was a risk factor for VTE the first year after discharge, the excess risk was not greater in patients with RA than in the general population.

Rapid increase in myocardial infarction risk following diagnosis of rheumatoid arthritis amongst patients diagnosed between 1995 and 2006

The risk of ischaemic heart disease (IHD), and in particular myocardial infarction (MI), is increased amongst patients with established rheumatoid arthritis (RA). Few studies have included contemporary patients with RA. We recently reported that the risk of IHD is not elevated before the onset of RA symptoms. However, when, in relation to RA diagnosis, the risk is increased is unknown.

OBJECTIVE

To assess the risk of MI and other IHD events amongst patients diagnosed with RA during the last decade and within 18 months following RA symptom onset, compared to the general population, by time since RA diagnosis, year of RA diagnosis and by rheumatoid factor (RF) status.

METHODS AND PATIENTS

A Swedish inception cohort of RA (n = 7469) diagnosed between 1995 and 2006 and a matched general population comparator cohort (n = 37,024), was identified and linked to national registers of morbidity and mortality from IHD. Relative risks (RRs) of MI and other IHD events were estimated using Cox regression.

RESULTS

During follow-up, 233 patients with RA and 701 controls developed a first MI, corresponding to an overall RR of MI of 1.6 (95% confidence interval 1.4, 1.9). Increased risks of MI were already detected within 1-4 years following RA diagnosis, as well as in patients diagnosed with RA during the last 5 years, in RF-negative patients and for transmural as well as nontransmural MIs.

CONCLUSIONS

MI risk increases rapidly following RA diagnosis, suggesting the importance of additional mechanisms other than atherosclerosis. The elevated short-term risk is present amongst patients diagnosed in recent years, underscoring the importance of MI prevention from the time of RA diagnosis.

No increased occurrence of ischemic heart disease prior to the onset of rheumatoid arthritis: results from two Swedish population-based rheumatoid arthritis cohorts

OBJECTIVE

To investigate the relative importance of shared etiologies for rheumatoid arthritis (RA) and ischemic heart disease (IHD) in terms of the well-known increased risk of IHD in patients with RA, by assessing the occurrence of IHD up until the time of the onset of the first symptoms of RA.

METHODS

We assessed the prevalence of a history of IHD, myocardial infarction (MI), and angina pectoris before the onset of RA symptoms in 2 large population-based case-control studies. Patients with newly diagnosed RA according to the criteria of the American College of Rheumatology were included as cases. We used data from the Swedish Early Arthritis Register study and the Swedish Epidemiologic Investigation of Rheumatoid Arthritis case-control study and from general population controls. Information on IHD, MI, and angina pectoris was obtained from the nationwide Hospital Discharge Register and from self reports. We calculated odds ratios (ORs) and 95% confidence intervals (95% CIs) to compare the prevalence of a history of IHD/MI/angina pectoris among patients with RA with that among population controls.

RESULTS

We could not detect any increased occurrence of IHD, MI, or angina pectoris before the onset of symptoms of RA, regardless of whether data on IHD were obtained from the Hospital Discharge Register or were self reported. As detected in the Hospital Discharge Register, the OR for IHD overall was 1.0 (95% CI 0.9-1.1), the OR for MI was 1.0 (95% CI 0.9-1.1), and the OR for angina pectoris was 1.0 (95% CI 0.9-1.2).

CONCLUSION

Shared risk factors or susceptibilities for RA and IHD are likely to contribute less than RA-related factors to the increased occurrence of IHD in patients with manifest RA. Nonetheless, the existence of shared factors associated with longer latency until the occurrence of IHD cannot be excluded.