***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: Background — Evidence about the effect of smoking on venous thromboembolism risk , generally and in the postoperative period , is limited and inconsistent . We examined the incidence of venous thromboembolism in relation to smoking habits , both in the absence of surgery and in the first 12 postoperative weeks , in a large prospect i ve study of women in the United Kingdom . Methods and Results — During 6 years ’ follow-up of 1 162 718 women ( mean age 56 years ) , 4630 were admitted to hospital for or died of venous thromboembolism . In the absence of surgery , current smokers had a significantly increased incidence of venous thromboembolism compared with never-smokers ( adjusted relative risk 1.38 , 95 % confidence interval 1.28–1.48 ) , with significantly greater risks in heavier than lighter smokers ( relative risks 1.47 [ 95 % confidence interval 1.34–1.62 ] and 1.29 [ 95 % confidence interval 1.17–1.42 ] for ≥15 versus < 15 cigarettes per day ) . Current smokers were also more likely to have surgery than never-smokers ( relative risk 1.12 , 95 % confidence interval 1.12–1.13 ) . Among women who had surgery , the incidence of venous thromboembolism in the first 12 postoperative weeks was significantly greater in current than never-smokers ( relative risk 1.16 , 95 % confidence interval 1.02–1.30 ) . Conclusions — Venous thromboembolism incidence was increased in current smokers , both in the absence of surgery and in the 12 weeks after surgery . Smoking is another factor to consider in the assessment of venous thromboembolism risk in patients undergoing surgery Emotional states of depression and loneliness are reported to be associated with higher risk and optimism with lower risk of arterial cardiovascular disease ( CVD ) and death . The relation between emotional states and risk of venous thromboembolism ( VTE ) has not been explored previously . We aim ed to investigate the associations between self-reported emotional states and risk of incident VTE in a population -based , prospect i ve study . The frequency of feeling depressed , lonely and happy/optimistic were registered by self-administered question naires , along with major co-morbidities and lifestyle habits , in 25,964 subjects aged 25 - 96 years , enrolled in the Tromsø Study in 1994 - 1995 .  Incident VTE-events were registered from the date of inclusion until September 1 , 2007 . There were 440 incident VTE-events during a median of 12.4 years of follow-up . Subjects who often felt depressed had 1.6-fold ( 95 % CI:1.02 - 2.50 ) higher risk of VTE compared to those not depressed in analyses adjusted for other risk factors ( age , sex , body mass index , oestrogens ) , lifestyle ( smoking , alcohol consumption , educational level ) and co-morbidities ( diabetes , CVD , and cancer ) . Often feeling lonely was not associated with VTE . However , the incidence rate of VTE in subjects who concurrently felt often lonely and depressed was higher than for depression alone ( age- and sex-adjusted incidence rate : 3.27 vs. 2.21 ) . Oppositely , subjects who often felt happy/optimistic had 40 % reduced risk of VTE ( HR 0.60 , 95 % CI : 0.41 - 0.87 ) . Our findings suggest that self-reported emotional states are associated with risk of VTE . Depressive feelings were associated with increased risk , while happiness/optimism was associated with reduced risk of VTE The objective of this study was to assess the influence of oral contraceptives ( OCs ) on the risk of venous thromboembolism ( VTE ) in young women . A 5-year case-control study including all Danish hospitals was conducted . All women 15 - 44 years old , suffering a first ever deep venous thrombosis or a first pulmonary embolism ( PE ) during the period January 1 , 1994 , to December 30 , 1998 , were included . Controls were selected annually , 600 per year in 1994 - 1995 and 1200 per year 1996 - 1998 . Response rates for cases and controls were 87.2 % and 89.7 % , respectively . After exclusion of nonvalid diagnoses , pregnant women , and women with previous thrombotic disease , 987 cases and 4054 controls were available for analysis . A multivariate , matched analysis was performed . Controls were matched to cases within 1-year age b and s. Adjustment was made for confounding influence ( if any ) from the following variables : age , year , body mass index , length of OC use , family history of VTE , cerebral thrombosis or myocardial infa rct ion , coagulopathies , diabetes , years of schooling , and previous birth . The risk of VTE among current users of OCs was primarily influenced by duration of use , with significantly decreasing odds ratios ( OR ) over time : < 1 year , 7.0 ( 5.1 - 9.6 ) ; 1 - 5 years , 3.6 ( 2.7 - 4.8 ) ; and > 5 years , 3.1 ( 2.5 - 3.8 ) , all compared with nonusers of OCs . After adjustment for confounders , current use of OCs with second- ( levonorgestrel or norgestimate ) and third- ( desogestrel or gestodene ) generation progestins when compared with nonuse result ed in ORs for VTE of 2.9 ( 2.2 - 3.8 ) and 4.0 ( 3.2 - 4.9 ) , respectively . After adjusting for progestin types and length of use , the risk decreased significantly with decreasing estrogen dose . With 30 - 40 microg as reference , 20 and 50 microg products implied ORs of 0.6 ( 0.4 - 0.9 ) and 1.6 ( 0.9 - 2.8 ) , respectively ( p(trend ) = 0.02 ) . After correction for duration of use and differences in estrogen dose , the third/second-generation risk ratio was 1.3 ( 1.0 - 1.8 ; p < 0.05 ) . In conclusion , use of OCs was associated significantly to the risk of VTE . The risk among current users was reduced by more than 50 % during the first years of use . The risk increased more than 100 % with increasing estrogen dose , and the difference in risk between users of third- and second-generation OCs , after correction for length of use and estrogen dose , was 33 % Background — Studies have suggested a link between risk factors for atherosclerotic disease and venous thromboembolism ( VTE ) , but results are heterogeneous . We sought to identify risk factors for VTE with a focus on risk factors for atherosclerotic disease . Methods and Results — Data were taken from the Copenhagen City Heart Study , a prospect i ve cohort study of a r and om , age-stratified sample of people living in a defined area in Copenhagen , Denmark , started in 1976 with follow-up until 2007 . First VTE ( deep vein thrombosis and pulmonary embolism ) diagnosis was retrieved from electronic national registries from study baseline to 2007 . Of 18 954 subjects ( median follow-up , 19.5 years ) representing 360 399 person-years of follow-up , 969 subjects experienced at least 1 VTE , corresponding to a crude incidence rate of 2.69 ( 95 % confidence interval [ CI ] , 2.52 to 2.86 ) per 1000 person-years . The variables found to be significantly associated with VTE in a multivariable model adjusted for age and calendar time were as follows : body mass index ( hazard ratio [ HR ] for ≥35 versus < 20=2.10 [ 95 % CI , 1.39 to 3.16 ] ) ; smoking ( HR for ≥25 g tobacco per day versus never smoker=1.52 [ 95 % CI , 1.15 to 2.01 ] ) ; gender ( HR for men versus women=1.24 [ 95 % CI , 1.08 to 1.42 ] ) ; household income ( HR for medium versus low=0.82 [ 95 % CI , 0.70 to 0.95 ] ) ; and diastolic blood pressure ( HR for > 100 versus < 80 mm Hg=1.34 [ 95 % CI , 1.08 to 1.66 ] ) . Other cardiovascular risk factors including total/high-density lipoprotein/low-density lipoprotein cholesterol levels , triglyceride levels , and diabetes mellitus were not associated with VTE . Conclusions — Obesity and smoking were both found to be important risk factors for VTE whereas total/high-density lipoprotein/low-density lipoprotein cholesterol levels , triglyceride levels , and diabetes mellitus were not The results of studies investigating the relationship of smoking with venous thrombosis are inconsistent . Therefore , in the MEGA study , a large population ‐based case – control study , we evaluated smoking as a risk factor for venous thrombosis and the joint effect with oral contraceptive use and the factor V Leiden mutation . Consecutive patients with a first venous thrombosis were included from six anticoagulation clinics . Partners of patients were asked to participate and additional controls were recruited using a r and om digit dialing method . Participants completed a st and ardized question naire . Individuals with known malignancies were excluded from the analyses , leaving a total of 3,989 patients and 4,900 controls . Current and former smoking result ed in a moderately increased risk of venous thrombosis ( odds ratio (OR)current 1.43 , 95 % confidence interval ( CI95 ) 1.28–1.60 , ORformer 1.23 , CI95 1.09–1.38 ) compared with nonsmoking . Adjustment for fibrinogen levels did not substantially change these risk estimates . A high number of pack‐years result ed in the highest risk among young current smokers ( OR≥20 pack‐years 4.30 , CI95 2.59–7.14 ) compared with young nonsmokers . Women who were current smokers and used oral contraceptives had an 8.8‐fold higher risk ( OR 8.79 , CI95 5.73–13.49 ) than nonsmoking women who did not use oral contraceptives . Relative to nonsmoking noncarriers , the joint effect of factor V Leiden and current smoking led to a 5.0‐fold increased risk ; for the prothrombin 20210A mutation this was a 6.0‐fold increased risk . In conclusion , smoking appears to be a risk factor for venous thrombosis with the greatest relative effect among young women using oral contraceptives . Am . J. Hematol . , 2008 . © 2007 Wiley‐Liss , OBJECTIVE To assess the relationship between  venous thromboembolic disease ( VTE )  and use of low-estrogen dose ( < 50 microg ) combined estrogen-progestin oral contraceptives ( OC ) and three thrombosis-related gene mutations in a United States population . DESIGN This case-control study was conducted in 1998 - 2000 among women ages 15 - 44 years who were members of the Kaiser Permanente Medical Care Program [ KPMCP ] ( Northern and Southern California ) . Cases were women with incident VTE ; about three times as many women frequency matched for age were r and omly selected as controls from the KPMCP membership in the same years . Data were collected in a 1 h face-to-face interview ; blood was drawn to extract DNA to test for gene polymorphisms . The analysis data set comprised 196 cases ( mean age 35.3 years ) and 746 controls ( mean age 36.2 years ) . RESULTS The adjusted odds ratio ( OR ) for VTE associated with current OC use was 4.07 ( 95 % confidence interval [ CI ] : 2.77 - 6.00 ) . The OR associated with OC use was higher for women who were obese than in the nonobese ( p = 0.01 for likelihood test for interaction ) and in women without predisposing medical conditions ( p = 0.02 for interaction ) . The adjusted OR for VTE was 7.10 ( 95 % CI : 2.33 - 21.61 ) in women with factor V Leiden ( G1691A ) mutation , 2.83 ( 95 % CI : 0.70 - 11.63 ) in women with prothrombin G20210A mutation and 0.26 ( 95 % CI : 0.10 - 0.65 ) in women with the MTHFR C677 T mutation . The OR for VTE in OC users with factor V Leiden mutation ( 11.32 ) was elevated more than in OC users without the mutation ( 3.20 ) and women with the mutation who were non-OC users ( 8.42 ) , but confidence intervals overlapped . CONCLUSIONS The risk of VTE is increased in users of  low-estrogen OC formulations . Obese women appear to be at greater risk of VTE when 
    Output:
    
Our findings show smoking is a risk factor for VTE with a dose-response relationship