***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: 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 % Objective To examine the risk of non-fatal idiopathic venous thromboembolism in current users of a combined oral contraceptive containing drospirenone  , relative to current users of preparations containing levonorgestrel .  Design Nested case-control study . Setting UK General Practice Research Data base . Participants Women aged 15 - 44 years without major risk factors for venous thromboembolism who started a new episode of use of an oral contraceptive containing 30 µg oestrogen in combination with either drospirenone or levonorgestrel between May 2002 and September 2009 . Cases were women with a first diagnosis of venous thromboembolism ; up to four controls , matched by age , duration of recorded information , and general practice , were r and omly selected for each case . Main outcome measures Odds ratios and 95 % confidence intervals estimated with conditional logistic regression ; age adjusted incidence rate ratio estimated with Poisson regression . Results 61 cases of idiopathic venous thromboembolism and 215 matched controls were identified . In the case-control analysis , current use of the drospirenone contraceptive was associated with a threefold higher risk of non-fatal idiopathic venous thromboembolism compared with levonorgestrel use ; the odds ratio adjusted for body mass index was 3.3 ( 95 % confidence interval 1.4 to 7.6 ) . Subanalyses suggested that referral , diagnostic , first time user , duration of use , and switching biases were unlikely explanations for this finding . The crude incidence rate was 23.0 ( 95 % confidence interval 13.4 to 36.9 ) per 100 000 woman years in current users of drospirenone and 9.1 ( 6.6 to 12.2 ) per 100 000 woman years in current users of levonorgestrel oral contraceptives . The age adjusted incidence rate ratio was 2.7 ( 1.5 to 4.7 ) . Conclusions These findings contribute to emerging evidence that the combined oral contraceptive containing drospirenone carries a higher risk of venous thromboembolism than do formulations containing levonorgestrel OBJECTIVES The " Long-term Active Surveillance Study for Oral Contraceptives " investigated the risks of long-term use of a 21-day regimen of drospirenone and ethinylestradiol ( DRSP ) compared to established oral contraceptives ( OCs ) in a routine clinical setting . STUDY DESIGN Prospect i ve , controlled , non-interventional cohort study conducted in seven European countries with three main exposure groups : new users of DRSP , levonorgestrel-containing OCs ( LNG ) , and OCs containing other progestogens ( Other OCs ) .  All self-reported clinical outcomes of interest ( OoI ) were vali date d via attending physicians and relevant source documents . Main OoI were serious clinical outcomes , in particular cardiovascular events . Comprehensive follow-up procedures were implemented . Statistical analyses were based on Cox regression models . RESULTS A total of 1,113 study centers enrolled 59,510 women . Overall 28 % , 26 % and 45 % of these women used DRSP , LNG and Other OCs , respectively . Study participants were followed for up to ten years ( mean value , 5.4years ) , which generated 318,784 woman-years ( WY ) of observation . Low loss to follow-up and drop-out rates of 2.9 % and 16.8 % were achieved . DRSP , LNG , and Other OCs showed similar incidence rates of venous thromboembolism . Corresponding hazard ratios ( HRs ) were close to unity . For arterial thromboembolic events ( ATE ) and initiation of antihypertensive treatment statistically significant lower risks were found for DRSP compared to LNG and Other OCs . CONCLUSION DRSP use was associated with similar general health risks and a low risk of ATE compared to OCs containing other progestogens . IMPLICATION STATEMENT The 21-day regimen of drospirenone-containing combined oral contraceptives is associated with similar risk of VTE compared to other combined oral contraceptives as well as potentially with a lower risk of ATE Abstract Objective : To test whether use of combined oral contraceptives containing third generation progestogens is associated with altered risk of venous thromboembolism .  Design : Matched case-control study . Setting : 10 centres in Germany and United Kingdom . Subjects : Cases were 471 women aged 16 - 44 who had a venous thromboembolism . Controls were 1772 women ( at least 3 controls per case ) unaffected by venous thromboembolism who were matched with corresponding case for age and for hospital or community setting . Main outcome measures : Odds ratios derived with stratified analyses and unconditional logistic regression to adjust for potential confounding variables . Results : Odds ratios ( 95 % confidence intervals ) for venous thromboembolism were : for any oral contraceptives versus no use , 4.0 ( 3.1 to 5.3 ) ; for second generation products ( low dose ethinyloestradiol , no gestodene or desogestrel ) versus no use , 3.2 ( 2.3 to 4.3 ) ; for third generation products ( low dose ethinyloestradiol , gestodene or desogestrel ) versus no use , 4.8 ( 3.4 to 6.7 ) ; for third generation products versus second generation products , 1.5 ( 1.1 to 2.1 ) ; for products containing gestodene versus second generation products , 1.5 ( 1.0 to 2.2 ) ; and for products containing desogestrel versus second generation products , 1.5 ( 1.1 to 2.2 ) . Probability of death due to venous thromboembolism for women using third generation products is about 20 per million users per year , for women using second generation products it is about 14 per million users per year , and for non-users it is five per million per year . Conclusions : Risk of venous thromboembolism was slightly increased in users of third generation oral contraceptives  compared with users of  second  generation products  . Key messages Key messages This case-control study examined risk of venous thromboembolism associated with different types of oral contraceptive Overall , there was a fourfold higher relative risk of thromboembolism associated with current use of any oral contraceptive versus no current use The risk of thromboembolism was 1.5 times higher for third generation contraceptives compared with second generation products Our data indicate the need for clinical prudence but allow doctors and women seeking contraception to exercise informed OBJECTIVES The study was conducted to compare risks of adverse cardiovascular and other events associated with the use of drospirenone (DRSP)-containing oral contraceptives ( OCs ) and other OCs .  METHODS AND MATERIAL S The European Active Surveillance study ( EURAS ) was a multinational , prospect i ve , noninterventional cohort study of new users of DRSP , levonorgestrel ( LNG ) and other progestin-containing OCs .  Semiannual follow-up was based on mailed question naires , with additional follow-up procedures when needed . RESULTS Overall , 58,674 women were followed for 142,475 women-years of observation . Loss to follow-up was 2.4 % . Serious adverse and fatal events were rare , and rate ratios were close to unity ( 1.0 ) . Cox regression analysis of cardiovascular outcomes yielded hazard ratios for DRSP-containing vs. LNG-containing and other OCs of 1.0 and 0.8 ( upper 95 % confidence limits , 1.8 and 1.3 ) for venous , and 0.3 and 0.3 ( upper 95 % confidence limits , 1.2 and 1.5 ) for arterial thromboembolism , respectively . CONCLUSIONS Risks of adverse cardiovascular and other serious events in users of a  DRSP-containing OC  are similar to those associated with the use of other OCs AIMS In October 1995 in response to the results of three studies , the Committee on the Safety of Medicines advised doctors and pharmacists that oral contraceptives containing desogestrel ( DSG ) and gestodene ( GST ) were associated with around a two-fold increase in the risk of thromboembolism compared with those containing other progestogens . The objective of this study was to estimate the risk of idiopathic venous thromboembolic disease ( VTE ) in users of combined oral contraceptives ( COCs )  , to compare the risk between formulations and to examine the effect of using age b and ing as opposed to matching by exact year of birth . METHODS A nested case control study was conducted using the General Practice Research Data base . Women with a VTE event recorded between 1992 and 1997 , who were treated with an anticoagulant , from consideration of their prescription records were likely to have been using a COC prescription on the day of the event and also had no exclusion factors , were deemed cases . For comparison with the previous studies , two nested case control studies were undertaken . Study 1 used controls matched by practice and year of birth . Study 2 used controls matched by practice and within 5 years age b and s. RESULTS We found an incidence of  idiopathic VTE amongst users of combined oral contraceptives of 3.8 per 10 000 exposed women years .  Incidence rates increased markedly after 35 years of age . The nested case-control study using controls matched by year of birth showed no significant difference in risk between the major COC formulations . With levonorgestrel ( LNG ) 150 microgram and ethinyloestradiol ( EE ) 30 microgram as the reference , the adjusted ORs for GST 75 microgram and EE 30 microgram was 1.3 ( 95 % CI 0.8 , 2.1 ) , for DSG 150 microgram and EE 30 microgram it was 1.0 ( 95 % CI 0.7 , 1.7 ) and for DSG 150 microgram and EE 20 microgram it was 0.8 ( 95 % CI 0.4 , 1.6 ) . Using less rigorous matching criteria , matching controls to cases within 5 years age b and s , the ORs increased . When a mixed group of COCs , characterized by having LNG as the progestogen component was used as the reference category , there was an elevation in the ORs for the newer products . We found a significant association between idiopathic VTE and current smoking ( OR 2.0 
    Output:
    
Compared with the use of levonorgestrel-containing COCs , the use of COCs containing other progestogens could be associated with a small increase in risk for VTE