Elsevier

The Lancet

Volume 379, Issue 9812, 21–27 January 2012, Pages 244-249
The Lancet

Articles
Risk of pulmonary embolism in patients with autoimmune disorders: a nationwide follow-up study from Sweden

https://doi.org/10.1016/S0140-6736(11)61306-8Get rights and content

Summary

Background

Some autoimmune disorders have been linked to venous thromboembolism. We examined whether there is an association between autoimmune disorders and risk of pulmonary embolism.

Methods

We followed up all individuals in Sweden without previous hospital admission for venous thromboembolism and with a primary or secondary diagnosis of an autoimmune disorder between Jan 1, 1964, and Dec 31, 2008, for hospital admission for pulmonary embolism. We obtained data from the MigMed2 database, which has individual-level information about all registered residents of Sweden. The reference population was the total population of Sweden. We calculated standardised incidence ratios (SIRs) for pulmonary embolism, adjusted for individual variables, including age and sex.

Findings

535 538 individuals were admitted to hospital because of an autoimmune disorder. Overall risk of pulmonary embolism during the first year after admission for an autoimmune disorder was 6·38 (95% CI 6·19–6·57). All the 33 autoimmune disorders were associated with a significantly increased risk of pulmonary embolism during the first year after admission. However, some had a particularly high risk—eg, immune thrombocytopenic purpura (10·79, 95% CI 7·98–14·28), polyarteritis nodosa (13·26, 9·33–18·29), polymyositis or dermatomyositis (16·44, 11·57–22·69), and systemic lupus erythematosus (10·23, 8·31–12·45). Overall risk decreased over time, from 1·53 (1·48–1·57) at 1–5 years, to 1·15 (1·11–1·20) at 5–10 years, and 1·04 (1·00–1·07) at 10 years and later. The risk was increased for both sexes and all age groups.

Interpretation

Autoimmune disorders are associated with a high risk of pulmonary embolism in the first year after hospital admission. Our findings suggest that these disorders in general should be regarded as hypercoagulable disorders.

Funding

Swedish Research Council, Swedish Council for Working Life and Social Research, Swedish Research Council Formas, Region Skåne.

Introduction

Venous thromboembolism is a major health problem,1 for which pulmonary embolism is a potentially lethal complication. Pulmonary embolism is a common cardiovascular and cardiopulmonary illness with a yearly incidence in the USA of more than one case per 1000 people and a mortality rate of more than 15% in the first 3 months after diagnosis,2 which is similar to that for acute myocardial infarction.3 Inflammation and venous thromboembolism are linked,4 with inflammation driving venous thrombosis. Inflammation modulates thrombotic responses by upregulating procoagulants, downregulating anticoagulants, and suppressing fibrinolysis.4 Therefore, autoimmune disorders such as inflammatory bowel disease,5, 6, 7, 8 Behçet's syndrome,9 rheumatoid arthritis,10 celiac disease,11 type-1 diabetes mellitus,12 systemic lupus erythematosus,13 hyperthyroidism,14 and Wegener's granulomatosis15 have been associated with an increased risk of venous thromboembolism. Autoimmune disorders are additional risk factors for venous thromboembolism in patients admitted to hospital;16 however, rheumatic disorders were not significant risk factors in the Medinox study.17

Previous studies of the association between venous thromboembolism and autoimmune diseases have often been small and done mostly in individual autoimmune diseases. We postulated that the inflammation associated with autoimmune disorders could affect the risk of pulmonary embolism in 33 autoimmmune diseases. We evaluated the risk of hospital admission with pulmonary embolism in all patients previously admitted with an autoimmune disorder in Sweden.

Section snippets

Data sources

We retrieved data from the MigMed2 database. This database contains information about all registered residents of Sweden for age, sex, occupation, region of residence, hospital diagnoses, dates of hospital admissions in Sweden (1964–2008), country of birth, parents’ country of birth, date of emigration, and date and cause of death. The database was constructed with several national Swedish data registers,18 including, but not limited to, the Swedish National Population and Housing Census

Results

Table 1 shows the number of patients in Sweden who were admitted to hospital with any of the 33 most common autoimmune disorders during the study period. 535 538 patients were admitted with an autoimmune disorder (table 1). The three most common autoimmune disorders were rheumatoid arthritis, Hashimoto's thyroiditis, and Graves’ disease (table 1). For the calculations of SIRs, we exluded 20 401 autoimmune patients because of previous admission for venous thromboembolism or coexisting venous

Discussion

Our results show that autoimmune disorders affect the risk of hospital admission for pulmonary embolism in men and women of all ages. The risk of pulmonary embolism during the first year after admission with an autoimmune disorder was high, and although it decreased over time, the overall risk remained for up to 10 years. Our results are consistent with previous findings linking inflammatory bowel disease,5, 6, 7, 8 Behçet's disease,9 rheumatoid arthritis,10 coeliac disease,11 type-1 diabetes

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