Venous thromboembolism does not share strong familial susceptibility with ischemic stroke: a nationwide family study in Sweden

The risk for venous thromboembolism and cardiometabolic disorders in offspring from thrombosis-prone pedigrees

BACKGROUND

Most family studies on venous thromboembolism (VTE) have focused on first-degree relatives.

OBJECTIVES

We took a pedigree-based approach and examined the risk of VTE and cardiometabolic disorders in offspring from extended pedigrees according to the densities of VTE in pedigrees.

METHODS

From the Swedish population, we identified a total of 482 185 pedigrees containing a mean of 14.2 parents, aunts/uncles, grandparents, and cousins of a core full sibship that we termed the pedigree offspring (n = 751 060). We then derived 8 empirical classes of these pedigrees based on the density of cases of VTE. The risk was determined in offspring for VTE and cardiometabolic disorders as a function of VTE density in their pedigrees. Bonferroni correction for multiple comparisons was performed.

RESULTS

VTE was unevenly distributed in the population; the Gini coefficient was 0.59. Higher VTE density in pedigrees was associated in the offspring with a higher risk of different VTE manifestations (deep venous thrombosis, pulmonary embolism, pregnancy-related VTE, unusual thrombosis, and superficial thrombophlebitis), thrombophilia, and lower age of first VTE event. Moreover, VTE density in pedigrees was significantly associated in the offspring with obesity, diabetes, gout, varicose veins, and arterial embolism and thrombosis (excluding brain and heart). No significant associations were observed for retinal vein occlusion, hypercholesterolemia, hypertension, coronary heart disease, myocardial infarction, ischemic stroke, atrial fibrillation, heart failure, primary pulmonary hypertension, cerebral hemorrhage, aortic aneurysm, peripheral artery disease, and overall mortality.

CONCLUSION

Offspring of pedigrees with a high density of VTE are disadvantaged regarding VTE manifestations and certain cardiometabolic disorders.

Risk of Stroke in Patients With Atrial Fibrillation Is Associated With Stroke in Siblings: A Nationwide Study

Background

It remains unclear whether heritable factors can contribute to risk stratification for ischemic stroke in patients with atrial fibrillation (AF). We examined whether having a sibling with ischemic stroke was associated with increased risk of ischemic stroke and mortality in patients with AF.

Methods and Results

In this nationwide study of the Swedish population, patients with AF and their siblings were identified from the Swedish patient registers and the Swedish MGR (Multi‐Generation Register). Ischemic stroke events were retrieved from the Swedish patient registers and CDR (Cause of Death Register). Risk of ischemic stroke was compared between patients with AF with and without a sibling affected by ischemic stroke, AF, or both ischemic stroke and AF. The total study population comprised 113 988 subjects (mean age, 60±12 years) diagnosed with AF between 1989 and 2012. In total, 11 709 of them were diagnosed with a first ischemic stroke and 20 097 died during a mean follow‐up time of 5.5 years for ischemic stroke and 5.9 years for mortality. After adjustment for covariates having a sibling with ischemic stroke, or both ischemic stroke and AF, was associated with increased risk of ischemic stroke (hazard ratio, 1.31; 95% CI, 1.23–1.40 or hazard ratio, 1.36; 95% CI, 1.24–1.49, respectively). Furthermore, ischemic stroke in a sibling was associated with all‐cause mortality (hazard ratio, 1.09; 95% CI, 1.05–1.14). In contrast, the risk of stroke was only marginally increased for patients with AF with a spouse affected by ischemic stroke.

Conclusions

Having a sibling affected by ischemic stroke confers an increased risk of ischemic stroke and death independently of traditional risk factors in patients with AF.

Family history of venous thromboembolism as a risk factor and genetic research tool

Familial clustering of venous thromboembolism (VTE) was described as far back as 1905 by Briggs. Although Egeberg discovered inherited deficiency of antithrombin in 1965, it was not until Dahlback discovered resistance to activated protein C in 1993 that it became clear that genetic factors are common risk factors of VTE. Several genes have been linked to familial aggregation of VTE and genome-wide association studies have found several novel gene loci. Still, it has been estimated that much of the heritability for VTE remains to be discovered. Family history (FH) of VTE is therefore still important to determine whether a patient has an increased genetic risk of VTE. FH has the potential to represent the sum of effects and interactions between environmental and genetic factors. In this article the design, methodology, results, clinical and genetic implications of FH studies of VTE are reviewed. FH in first-degree relatives (siblings and/or parents) is associated with a 2–3 times increased familial relative risk (FRR). However, the FRR is dependent on age, number of affected relatives, and presentation of VTE (provoked/unprovoked). Especially high familial risks are observed in individuals with two or more affected siblings (FFR> 50). However, the familial risk for recurrent VTE is much lower or non-significant. Moreover, FH of VTE appears mainly to be important for venous diseases (i. e. VTE and varicose veins). The familial associations with other diseases are weaker. In conclusion, FH of VTE is an important research tool and a clinically potential useful risk factor for VTE.

Venous thromboembolism and varicose veins share familial susceptibility: a nationwide family study in Sweden

Background

Varicose veins (VVs) have been associated with venous thromboembolism (VTE), but whether these diseases share familial susceptibility has not been determined. This nationwide study aimed to determine whether VTE shares familial susceptibility with VVs.

Methods and Results

Swedish Multigeneration Register data for persons aged 0 to 76 years during the period 1964–2008 were linked to the Swedish Inpatient and Outpatient Registers. Familial risks (standardized incidence ratios [SIRs]) of VTE and VVs were examined in 2 ways (ie, bidirectionally): risk of VTE in subjects whose siblings had been diagnosed with VVs and risk of VVs in persons whose siblings had been diagnosed with VTE. The analyses were repeated for spouses to determine the importance of shared adult family environment. In total, 96 810 siblings had VVs and 87 564 had VTE. An increased risk of VTE was observed in persons whose siblings had VVs (SIR 1.30, 95% CI 1.26 to 1.33), whereas persons whose siblings had VTE had an increased risk of VVs (SIR 1.30, 95% CI 1.27 to 1.34). If 2 or more siblings were affected by VTE, the risk for VVs was 1.70 (95% CI 1.53 to 1.88). Conversely, if 2 or more siblings were affected by VVs, the risk for VTE was 1.52 (95% CI 1.38 to 1.67). In spouses of VTE patients, a minor increased risk of VVs was observed (SIR 1.05 for husbands, SIR 1.06 for wives). The risk of VTE in spouses of VV patients was similarly small (SIR 1.01 for husbands, SIR 1.05 for wives).

Conclusions

VVs and VTE share familial susceptibility. This novel finding suggests the existence of shared familial and possibly genetic factors.

High familial risk of atrial fibrillation/atrial flutter in multiplex families: a nationwide family study in Sweden

BACKGROUND

Although the heritability of atrial fibrillation/atrial flutter (AF/AFl) has been determined, the familial risk in multiplex families is unclear. The main aim of this nationwide study was to determine the familial risk of AF/AFl in multiplex families.

METHODS AND RESULTS

We examined the familial risk of AF/AFl in the entire Swedish population. We linked Multigeneration Register data on individuals aged 0 to 76 years with Hospital Discharge Register data for 1987-2008 and Outpatient Register data for 2001-2008 to compare AF/AFl risk among relatives of all 300 586 individuals with AF/AFl with that among relatives of unaffected individuals. We used conditional logistic regression to investigate differences in exposure between cases and controls. Parents (odds ratio [OR] 1.95 [95% CI 1.89 to 2.00]) and siblings (OR=3.08 [3.00 to 3.16]) of cases had higher odds of AF/AFl than did parents and siblings of controls. AF/AFl ORs were increased in both sexes. For 2% of cases, both parents had AF/AFl, compared with only 0.7% of controls (OR=3.60 [3.30 to 3.92]). Moreover, 3% of cases had ≥2 siblings with AF/AFl, compared with 1% of controls (OR=5.72 [5.28 to 6.19]). In premature cases (diagnosed at age <50 years), the ORs were 5.04 (4.36 to 5.82) and 8.51 (6.49 to 11.15) for AF/AFl in both parents and AF/AFl in ≥2 siblings, respectively. The overall spouse OR was 1.16 (1.13 to 1.19).

CONCLUSIONS

Family history of AF/AFl increases the odds of AF/AFl in first-degree relatives. High familial risks were observed in multiplex families.

Family history as a risk factor for recurrent hospitalization for lone atrial fibrillation: a nationwide family study in Sweden

BACKGROUND

Although the heritability of atrial fibrillation (AF) has been determined, the relevance of family history of AF for the likelihood of recurrent hospitalization for AF is unknown. The aim of this nationwide study was to determine whether family history of AF is a risk factor of recurrent hospitalization for lone AF (LAF), i.e., AF with unknown etiology. The familial risk for first time LAF hospitalization was also determined and compared to the risk of recurrent hospitalization for LAF.

METHODS

We examined whether family history of AF is a risk factor for recurrent hospitalization for LAF in the whole Swedish population. We linked Multigeneration Register data on individuals aged 0-60 years to Hospital Discharge Register data for the period 1987-2009 to compare LAF recurrent hospitalization risk among individuals with and without parental or sibling history of AF. We calculated hazard ratios (HRs) to determine the familial HR of recurrent hospitalization for LAF. Odds ratios (OR) were calculated for familial risk of first time LAF hospitalization.

RESULTS

The risk of recurrent LAF hospitalization was 1.23 (95% CI 1.17-1.30) for individuals with affected parents compared to 1.30 (95% CI 1.22-1.38) for those with affected siblings. After 10 years of follow up 50% of those without and 60% of those with family history had recurrent hospitalization for LAF. The risk of recurrent LAF hospitalization in individuals with two affected parents was 1.65 (95% CI 1.44-1.90). There was an interaction between age and family history, with family history having a weaker effect on LAF hospitalization risk in older age groups. The OR for first time LAF hospitalization was 2.08 (95% CI 2.02-2.15) for offspring with affected parents and 3.23 (95% CI 3.08-3.39) for individuals with affected siblings.

CONCLUSIONS

Family history of AF is a novel risk factor for recurrent LAF hospitalization. The higher recurrence hospitalization risk in multiplex families and younger individuals suggests a genetic contribution. However, the familial risk for recurrent LAF hospitalization was much lower than the risk for first time LAF hospitalization, suggesting that familial and possibly genetic factors are more important for first time LAF hospitalization than recurrent LAF hospitalization.