Body height, mobility, and risk of first and recurrent venous thrombosis

Proportion of venous thromboembolism attributed to recognized prothrombotic genotypes in men and women

Background

Data on the proportion of venous thromboembolism (VTE) risk attributed to prothrombotic genotypes in men and women are limited.

Objectives

We aimed to estimate the population attributable fraction (PAF) of VTE for recognized, common prothrombotic genotypes in men and women using a population-based case cohort.

Methods

Cases with incident VTE (n = 1493) and a randomly sampled subcohort (n = 13,069) were derived from the Tromsø study (1994-2012) and the Trøndelag Health Study (1995-2008) cohorts. DNA samples were genotyped for 17 single-nucleotide polymorphisms (SNPs) previously associated with VTE. PAFs with 95% bias-corrected CIs (based on 10,000 bootstrap samples) were estimated for SNPs significantly associated with VTE, and a 6-SNP cumulative model was constructed for both sexes.

Results

In women, the individual PAFs for SNPs included in the cumulative model were 16.9% for ABO (rs8176719), 17.6% for F11 (rs2036914), 15.1% for F11 (rs2289252), 8.7% for FVL (rs6025), 6.0% for FGG (rs2066865), and 0.2% for F2 (rs1799963). The cumulative PAF for this 6-SNP model was 37.8%. In men, the individual PAFs for SNPs included in the cumulative model were 21.3% for ABO, 12.2% for F11 (rs2036914), 10.4% for F11 (rs2289252), 7.5% for FVL, 7.8% for FGG, and 1.1% for F2. This resulted in a cumulative PAF in men of 51.9%.

Conclusion

Our findings in a Norwegian population suggest that 52% and 38% of the VTEs can be attributed to known prothrombotic genotypes in men and women, respectively.

Sex-specific aspects of venous thromboembolism: What is new and what is next?

Men seem to have a higher intrinsic risk of venous thromboembolism (VTE) than women, regardless of age. To date, this difference has not been explained. By integrating state-of-the-art research presented at the International Society on Thrombosis and Haemostasis Congress of 2021 with the available literature, we address potential explanations for this intriguing risk difference between men and women. We discuss the role of exogenous and endogenous sex hormones as the most important known sex-specific determinants of VTE risk. In addition, we highlight clues on the role of sex hormones and VTE risk from clinical scenarios such as pregnancy and the polycystic ovary syndrome. Furthermore, we address new potential sex-specific risk factors and unanswered research questions, which could provide more insight in the intrinsic risk difference between men and women, such as body height and differences in body fat distribution, leading to dysregulation of metabolism and inflammation.

Varicose Veins and Risk of Venous Thromboembolic Diseases: A Two-Sample-Based Mendelian Randomization Study

Background

Varicose veins are found to be associated with increased risk of venous thromboembolism (VTE) in many observational studies, but whether varicose veins are causally associated with VTE remains unclear. Therefore, we used a series of Mendelian randomization (MR) methods to investigate that association.

Methods

23 independent single-nucleotide polymorphisms (SNPs) for varicose veins were obtained from the Pan UK Biobank analysis. The outcomes datasets for deep vein thrombosis (DVT), pulmonary embolism (PE) and venous thromboembolism (VTE) were obtained from the FinnGen study. Before analysis, body mass index (BMI) and height were included as confounders in our MR model. Basic MR [inverse-variance weighted (IVW), weight-median, penalized weighted-median and MR-Egger methods] and MR-PRESSO were performed against each outcome using the whole SNPs and SNPs after excluding those associated with confounders. If causal associations were suggested for any outcome, a basic MR validation analysis, a multivariable MR analysis with BMI and height, a Causal Analysis Using Summary Effect estimates (CAUSE), and a two-step MR analysis with BMI and height, would follow.

Results

Using 21 qualified SNPs, the IVW method (OR: 1.173, 95% CI: 1.070-1.286, p < 0.001, FDR = 0.002), the weighted median method (OR: 1.255, 95% CI: 1.106-1.423, p < 0.001, FDR = 0.001), the penalized weighted median method (OR: 1.299, 95% CI: 1.128-1.495, p < 0.001, FDR = 0.001) and the MR-PRESSO (OR: 1.165, 95% CI: 1.067-1.273, p = 0.003, FDR = 0.009) suggested potential causal effect of varicose veins on DVT, but no cause effect was found for PE and VTE. Excluding SNPs associated with confounders yielded similar results. The causal association with DVT was validated using a self-reported DVT cohort (IVW, OR: 1.107, 95% CI: 1.041-1.178, p = 0.001). The causal association maintained after adjustment for height (OR = 1.105, 95% CI: 1.028-1.188, p = 0.007), BMI (OR = 1.148, 95% CI: 1.059-1.244, p < 0.001) and them both (OR = 1.104, 95% CI: 1.035-1.177, p = 0.003). The causal association also survived the strict CAUSE (p = 0.018). Finally, in two-step MR, height and BMI were found to have causal effects on both varicose veins and DVT.

Conclusion

Genetically predicted varicose veins may have a causal effect on DVT and may be one of the mediators of obesity and taller height that predispose to DVT.

Exploring Opportunities for Primary Prevention of Unprovoked Venous Thromboembolism: Ready for Prime Time?

Venous thromboembolism (VTE) is an important vascular disease and public health problem. Prevention of VTE has focused mainly on using thromboprophylaxis to avoid provoked VTE or recurrent VTE, with little attention paid to the possibility of preventing the one third to one half of VTEs that are unprovoked. We review growing research suggesting that unhealthy lifestyle risk factors may cause a considerable proportion of unprovoked VTE. Using epidemiologic data to calculate population attributable risks, we estimate that in the United States obesity may contribute to 30% of VTEs, physical inactivity to 4%, current smoking to 3%, and Western dietary pattern to 11%. We also review possibilities for VTE primary prevention either through a high-risk individual approach or a population-wide approach. Interventions for outpatients at high VTE risk but without VTE provoking factors have not been fully tested; yet, improving patient awareness of risk and symptoms, lifestyle counseling, and possibly statins or direct oral anticoagulants may prove useful in primary prevention of unprovoked VTE. A population approach to prevention would bolster awareness of VTE and aim to shift lifestyle risk factors downward in the whole population using education, environmental changes, and policy. Assuming the epidemiological associations are accurate, causal, and independent of each other, a reduction of obesity, physical inactivity, current smoking, and Western diet by 25% in the general population might reduce the incidence of unprovoked VTE by 12%. We urge further research and consideration that primary prevention of unprovoked VTE may be a worthwhile public health aim.

Physical activity and risk of recurrence and mortality after incident venous thromboembolism

BACKGROUND

Limited data exist on the relationship between physical activity and major complications after incident venous thromboembolism (VTE).

OBJECTIVES

To investigate whether physical activity was associated with risk of recurrence and mortality in patients with VTE recruited from the general population.

METHODS

Patients with incident VTE (n = 786) derived from the Tromsø Study surveys 4-6 (1994-1995, 2001-2002, and 2007-2008) were included, and data on physical activity were dichotomized according to the activity level reported in the survey preceding the incident VTE (inactive: <1 hour per week, active: ≥1 hour per week). Recurrent VTE and all-cause mortality were registered up to December 31, 2015. Hazard ratios (HRs) for recurrence and all-cause mortality were calculated using Cox regression models with the inactive group as reference.

RESULTS

There were 139 recurrences and 395 deaths during follow-up. Physical activity was not associated with the risk of recurrence in men (HR model 2: 1.48, 95% confidence interval [CI] 0.83-2.65) or in women (HR model 2: 0.95, 95% CI 0.52-1.74). In contrast, physical activity was associated with a 28% lower risk of mortality during 10 years of follow up (HR model 3: 0.72, 95% CI 0.57-0.91). The inverse association was stronger in patients with a first deep vein thrombosis ( HR model 2: 0.59, 95% CI 0.44-0.79) than a pulmonary embolism (HR model 3: 0.87, 95% CI 0.61-1.26).

CONCLUSION

Our results suggest that habitual physical activity prior to incident VTE does not influence the risk of recurrence. In contrast, active individuals were at lower risk of mortality, particularly following deep vein thrombosis.

Risk of Recurrent Venous Thromboembolism After an Initial Episode: Risk Stratification and Implications for Long-term Treatment

PURPOSE OF REVIEW

Venous thromboembolism (VTE) is a common condition with significant associated morbidity and mortality. Recurrent VTE after an initial episode is a preventable medical condition. The following review discusses data supporting recurrence risk estimates after an initial VTE episode as well as treatment strategies to mitigate risk of recurrent VTE.

RECENT FINDINGS

This review particularly highlights methods for stratifying the risk of recurrent VTE and recent studies that have evaluated direct oral anticoagulants for the prevention of recurrent VTE. Risk assessment for VTE recurrence should guide anticoagulation duration. In patients who present with unprovoked VTE events, there remains a high risk of recurrence that is significantly mitigated with extended duration anticoagulation with either a vitamin K antagonist or direct oral anticoagulant.

Adult height and risk of 50 diseases: a combined epidemiological and genetic analysis

BACKGROUND

Adult height is associated with risk of several diseases, but the breadth of such associations and whether these associations are primary or due to confounding are unclear. We examined the association of adult height with 50 diseases spanning multiple body systems using both epidemiological and genetic approaches, the latter to identify un-confounded associations and possible underlying mechanisms.

METHODS

We examined the associations for adult height (using logistic regression adjusted for potential confounders) and genetically determined height (using a two-sample Mendelian randomisation approach with height-associated genetic variants as instrumental variables) in 417,434 individuals of white ethnic background participating in the UK Biobank. We undertook pathway analysis of height-associated genes to identify biological processes that could link height and specific diseases.

RESULTS

Height was associated with 32 diseases and genetically determined height associated with 12 diseases. Of these, 11 diseases showed a concordant association in both analyses, with taller height associated with reduced risks of coronary artery disease (odds ratio per standard deviation (SD) increase in height OR_epi = 0.80, 95% CI 0.78-0.81; OR per SD increase in genetically determined height OR_gen = 0.86, 95% CI 0.82-0.90), hypertension (OR_epi = 0.83, 95% CI 0.82-0.84; OR_gen = 0.88, 95% CI 0.85-0.91), gastro-oesophageal reflux disease (OR_epi = 0.85, 95% CI 0.84-0.86; OR_gen = 0.94, 95% CI 0.92-0.97), diaphragmatic hernia (OR_epi = 0.81, 95% CI 0.79-0.82; OR_gen = 0.91, 95% CI 0.88-0.94), but increased risks of atrial fibrillation (OR_epi = 1.42, 95% CI 1.38-1.45; OR_gen = 1.33, 95% CI 1.26-1.40), venous thromboembolism (OR_epi = 1.18, 95% CI 1.16-1.21; OR_gen = 1.15, 95% CI 1.11-1.19), intervertebral disc disorder (OR_epi = 1.15, 95% CI 1.13-1.18; OR_gen = 1.14, 95% CI 1.09-1.20), hip fracture (OR_epi = 1.19, 95% CI 1.12-1.26; OR_gen = 1.27, 95% CI 1.17-1.39), vasculitis (OR_epi = 1.15, 95% CI 1.11-1.19; OR_gen = 1.20, 95% CI 1.14-1.28), cancer overall (OR_epi = 1.09, 95% CI 1.08-1.11; OR_gen = 1.06, 95% CI 1.04-1.08) and breast cancer (OR_epi = 1.08, 95% CI 1.06-1.10; OR_gen = 1.07, 95% CI 1.03-1.11). Pathway analysis showed multiple height-associated pathways associating with individual diseases.

CONCLUSIONS

Adult height is associated with risk of a range of diseases. We confirmed previously reported height associations for coronary artery disease, atrial fibrillation, venous thromboembolism, intervertebral disc disorder, hip fracture and cancer and identified potential novel associations for gastro-oesophageal reflux disease, diaphragmatic hernia and vasculitis. Multiple biological mechanisms affecting height may affect the risks of these diseases.

Body Height and Incident Risk of Venous Thromboembolism: A Cosibling Design

BACKGROUND

Body height has been associated with an increased risk of venous thromboembolism (VTE), but the association can be confounded with shared familial factors (genetic/environmental). A cosibling design is useful for deeper understanding about the relationship between VTE and height.

METHODS AND RESULTS

From Swedish national registry databases, we used a corelative design with full siblings alongside a general Swedish population sample. A cohort of male conscripts (n=1 610 870), born in 1951 to 1992 without previous VTE, was followed from enlistment (1969-2010) until 2012. Another cohort of first-time pregnant women (n=1 093 342) from the medical birth register, without previous VTE, was followed from first pregnancy (1982-2012) until 2012. Using the Multi-Generation Register, we identified all full-sibling pairs discordant for height. This cosibling design allowed for adjustment for familial factors (genetic/environmental). Compared with the tallest women (>185 cm) and men (>190 cm), there was a graded decreased risk by lower height for both men and women. The risk was lowest in women and men with the shortest stature (<155 and <160 cm, respectively): hazard ratios=0.31 (95% confidence interval, 0.22-0.42) and 0.35 (95% confidence interval, 0.22-0.55), respectively. There was a graded association also in the cosibling design comparing siblings with varying degree of discordance for height (reference was the taller sibling): ≥10 cm difference between brothers hazard ratios=0.69 (95% confidence interval, 0.61-0.78) and sisters hazard ratios=0.65 (95% confidence interval, 0.52-0.80), respectively.

CONCLUSIONS

Height is an independent predictor of VTE. The use of sibling pairs reduces the likelihood that familial confounding explains the results. The findings are important for the understanding of the pathogenesis of VTE.

TV viewing and incident venous thromboembolism: the Atherosclerotic Risk in Communities Study

TV viewing is associated with risk of arterial vascular diseases, but has not been evaluated in relation to venous thromboembolism (VTE) risk in Western populations. In 1987-1989, the Atherosclerosis Risk in Communities Study obtained information on the frequency of TV viewing in participants aged 45-64 and followed them prospectively. In individuals free of prebaseline VTE (n = 15, 158), we used a Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of incident VTE according to frequency of TV viewing ("Never or seldom", "Sometimes", "Often" or "Very often"). During the 299,767 person-years of follow-up, we identified 691 VTE events. In a multivariable-adjusted model, the frequency of TV viewing showed a positive dose-response relation with VTE incidence (P for trend = 0.036), in which "very often" viewing TV carried 1.71 (95% CI 1.26-2.32) times the risk of VTE compared with "never or seldom" viewing TV. This association to some degree was mediated by obesity (25% mediation, 95% CI 10.7-27.5). Even among individuals who met a recommended level of physical activity, viewing TV "very often" carried 1.80 (1.04-3.09) times the risk of VTE, compared to viewing TV "never or seldom". Greater frequency of TV viewing was independently associated with increased risk of VTE, partially mediated by obesity. Achieving a recommended physical activity level did not eliminate the increased VTE risk associated with frequent TV viewing. Avoiding frequent TV viewing as well as increasing physical activity and controlling body weight might be beneficial for VTE prevention.

Mild antithrombin deficiency and risk of recurrent venous thromboembolism: results from the MEGA follow-up study

Essentials Mild antithrombin deficiency may increase the risk of recurrent venous thromboembolism (VTE). In a cohort study, we stratified patients with VTE to various cut-off antithrombin levels. A 1.6-3.7-fold increased risk of recurrent VTE was observed in the lowest antithrombin categories. Mild antithrombin deficiency (activity < 5th percentile of normal) increases recurrent VTE risk.

SUMMARY

Background Mild antithrombin deficiency (previously defined as antithrombin activity below 70% or 80%) has been associated with a 2.4-3.5-fold increased risk of recurrent venous thromboembolism (VTE). This finding may have implications for duration of antithrombotic therapy in VTE patients with mild antithrombin deficiency. Objectives To externally validate whether mild antithrombin deficiency is a risk factor for recurrent VTE. Methods In a population-based cohort study, patients with a first VTE (n = 2357) were stratified according to percentile cut-off antithrombin levels (< 5th [< 87%], 5-10th [87-92%], > 10th percentile [> 92%]) and functional antithrombin levels (< 70%, 70-80%, > 80%). Results During a median follow-up of 7.4 years, 361 recurrent events occurred (incidence rate, 2.5/100 patient-years). We observed an increased risk of recurrent VTE in the lowest antithrombin activity category (< 5th percentile; < 87%) as compared with antithrombin activity that was > 10th percentile (> 92%), with an adjusted hazard ratio (HR) of 1.5 (95%CI, 1.0-2.3). When analyses were stratified to antithrombin cut-off criteria of< 70% vs. patients with antithrombin activity > 80%, the adjusted HR for venous recurrence was 3.7 (95% CI, 1.4-9.9). Mild antithrombin deficiency was able to predict recurrent VTE over at least 8 years of follow-up and the association remained present when the population was stratified to the presence or absence of thrombosis risk factors. Restriction analyses, where patients who used anticoagulation at time of blood draw and those who reported drinking ≥ 5 glasses alcohol daily were excluded, did not materially affect these outcomes. Conclusion This study confirms that mild antithrombin deficiency is a risk factor for recurrent VTE.

Joint effects of prothrombotic genotypes and body height on the risk of venous thromboembolism: the Tromsø study

Essentials Body height and prothrombotic genotypes are associated with risk of venous thromboembolism (VTE). The joint effect of prothrombotic genotypes and tall stature on VTE risk is scarcely investigated. We investigated the joint effect of prothrombotic genotypes and tall stature on VTE risk. Prothrombotic genotypes did not yield excess risk of VTE in subjects with a tall stature.

SUMMARY

Background Studies have reported synergistic effects of prothrombotic single-nucleotide polymorphisms (SNPs) and obesity on the risk of venous thromboembolism (VTE). Tall stature is associated with an increased VTE risk, but the joint effect of prothrombotic genotypes and tall stature on the VTE risk is unknown. Aims To investigate the joint effects of prothrombotic genotypes and tall stature on the VTE risk. Methods Cases with incident VTE (n = 676) and a randomly selected age-weighted subcohort (n = 1842) were sampled from the Tromsø study (cohort follow-up: 1994-2012). DNA was genotyped for rs6025 (factor V Leiden), rs1799963 (FII), rs8176719 (ABO blood group), rs2066865 (fibrinogen-γ), and rs2036914 (FIX). Age-adjusted and sex-adjusted hazard ratios (HRs) of VTE were calculated by categories of risk alleles (de Haan 5-SNP score: 0-1, 2-3, and ≥ 4) and body height (< 40th, 40th-80th and > 80th percentiles). Results The VTE risk increased by increasing category of body height, and subjects with height ≥ 178 cm had a two-fold higher VTE risk (HR 2.03; 95% confidence interval [CI] 1.51-2.73) than those with height ≤ 165 cm. The VTE risk also increased across categories of risk alleles. However, the combination of a tall stature and risk alleles, either individual SNPs or risk score, did not result in an excess VTE risk. Subjects with four or more risk alleles and height ≥ 178 cm had a two-fold (HR 2.08; 95% CI 1.24-3.52) higher VTE risk than subjects ≤ 165 cm with no risk allele or one risk allele. Conclusions In contrast to obesity, the presence of prothrombotic genotypes did not result in an excess VTE risk in subjects with a tall stature.

Taller height as a risk factor for venous thromboembolism: a Mendelian randomization meta-analysis

Essentials Observational data suggest taller people have a higher risk of venous thromboembolism (VTE). We used Mendelian randomization techniques to further explore this association in three studies. Risk of VTE increased by 30-40% for each 10 cm increment in height. Height was more strongly associated with deep vein thrombosis than with pulmonary embolism.

SUMMARY

Background Taller height is associated with a greater risk of venous thromboembolism (VTE). Objectives To use instrumental variable (IV) techniques (Mendelian randomization) to further explore this relationship. Methods Participants of European ancestry were included from two cohort studies (Atherosclerosis Risk in Communities [ARIC] study and Cardiovascular Health Study [CHS]) and one case-control study (Mayo Clinic VTE Study [Mayo]). We created two weighted genetic risk scores (GRSs) for height; the full GRS included 668 single-nucleotide polymorphisms (SNPs) from a previously published meta-analysis, and the restricted GRS included a subset of 362 SNPs not associated with weight independently of height. Standard logistic regression and IV models were used to estimate odds ratios (ORs) for VTE per 10-cm increment in height. ORs were pooled across the three studies by the use of inverse variance-weighted random effects meta-analysis. Results Among 9143 ARIC and 3180 CHS participants free of VTE at baseline, there were 367 and 109 incident VTE events. There were 1143 VTE cases and 1292 controls included from Mayo. The pooled ORs from non-IV models and models using the full and restricted GRSs as IVs were 1.27 (95% confidence interval [CI] 1.11-1.46), 1.34 (95% CI 1.04-1.73) and 1.45 (95% CI 1.04-2.01) per 10-cm greater height, respectively. Conclusions Taller height is associated with an increased risk of VTE in adults of European ancestry. Possible explanations for this association, including taller people having a greater venous surface area, a higher number of venous valves, or greater hydrostatic pressure, need to be explored further.

Thrombosis Related ABO, F5, MTHFR, and FGG Gene Polymorphisms in Morbidly Obese Patients

Objective. Obesity is a well-known risk factor for thrombotic complications. The aim of the present study was to determine the frequency of thrombosis related ABO, F5, MTHFR, and FGG gene polymorphisms in morbidly obese patients and compare them with the group of nonobese individuals. Methods. Gene polymorphisms were analyzed in 320 morbidly obese patients (BMI > 40 kg/m²) and 303 control individuals (BMI < 30 kg/m²) of European descent. ABO C>T (rs505922), F5 C>G (rs6427196), MTHFR C>T (rs1801133), and FGG C>T (rs6536024) SNPs were genotyped by RT-PCR. Results. We observed a tendency for MTHFR rs1801133 TT genotype to be linked with morbid obesity when compared to CC genotype; however, the difference did not reach the significant P value (OR 1.84, 95% CI 0.83–4.05, P = 0.129). Overall, the genotypes and alleles of rs505922, rs6427196, rs1801133, and rs6536024 SNPs had similar distribution between morbidly obese and nonobese control individuals. Distribution of height and weight means among individuals carrying different rs505922, rs6427196, rs1801133, and rs6536024 genotypes did not differ significantly. Conclusions. Gene polymorphisms ABO C>T (rs505922), F5 C>G (rs6427196), MTHFR C>T (rs1801133), and FGG C>T (rs6536024) were not associated with height, weight, or morbid obesity among European subjects.

Predictors of active cancer thromboembolic outcomes: validation of the Khorana score among patients with lung cancer

Essentials Venous thromboembolism (VTE) prevention strategies require effective risk assessment models. We sought to validate the Khorana Risk Score (KRS) in patients with lung cancer. A high KRS was not predictive of VTE but was independently associated with all-cause mortality. Our findings stress the need for a lung cancer-specific VTE risk assessment model.

SUMMARY

Objectives Lung cancer is strongly associated with venous thromboembolism (VTE), but primary prevention against VTE is not a validated management strategy. Risk assessment models will be necessary for efficient implementation of preventative strategies. Materials and methods Utilizing a prospectively collected lung cancer database, we aimed to validate the Khorana Risk Score (KRS) in the prediction of VTE among patients with lung cancer. VTE events were retrospectively identified by reviewers unaware of the clinical prediction score calculation. The association between KRS and the risk of VTE was examined using cumulative incidence function with competing risk models. Mortality prediction was evaluated as a secondary outcome. Results We included 719 patients in our review. The patients were predominantly older men with non-small cell lung cancer and 40% had metastatic disease at inception. The median follow-up was 15.2 months. There were 83 VTEs (11.5%) and 568 (78.8%) patients died. A high KRS (cumulative incidence, 12.4%; 95% confidence interval [CI], 6.4-20.5%) was not associated with VTE compared with an intermediate score (cumulative incidence, 12.1%; 95% confidence interval, 9.5-15.0%) in both univariate and multivariable analyses. However, a high KRS was a predictor of mortality (hazard ratio, 1.7; 95% CI, 1.4-2.2). Conclusions Among patients with lung cancer, the KRS did not stratify the patients at the highest risk of VTE. Improved risk stratification methods are needed for this group of patients prior to implementing a primary prevention strategy.

Sex difference in the risk of recurrent venous thrombosis: a detailed analysis in four European cohorts

BACKGROUND

Previous analyses reported a higher risk of recurrent venous thrombosis in men than women.

OBJECTIVES

We aimed to assess the risk of recurrence in men compared with women whilst taking female reproductive risk factors (oral contraception, postmenopausal hormone therapy and pregnancy) into account. In addition, we hypothesized that the sex difference in venous thrombosis was related to F9 Malmö, an X-linked prothrombotic factor.

METHODS

In four pooled European cohorts (CARROT study, Glasgow, UK; CVTE study, Cambridge, UK; AUREC study, Vienna, Austria; and LETS follow-up study, Leiden, the Netherlands), the risk of recurrent venous thrombosis was calculated in men, women with reproductive risk factors and women without reproductive risk factors at the time of their first venous thrombosis. F9 Malmö was genotyped and carriers and non-carriers contrasted.

RESULTS

In total, 2185 patients with a first venous thrombosis, 1043 men and 1142 women, were included. Overall, men had a 2.8-fold (95% confidence interval [CI], 2.2-3.4) higher risk of recurrent venous thrombosis than women. This risk was 5.2-fold (95% CI, 3.5-7.7) higher in men than in women with reproductive risk factors, and 2.3-fold (95% CI, 1.7-3.2) higher in men than in women without reproductive risk factors. No difference in risk of recurrence was found for carriers vs. non-carriers of F9 Malmö.

CONCLUSION

Men experienced a recurrent venous thrombosis twice as often as women without reproductive risk factors. These findings indicate that men have a higher intrinsic risk of venous thrombosis than women, which is partly masked by female reproductive risk factors. The sex difference cannot be explained by F9 Malmö.