***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 purpose of this study was to compare circadian blood pressure and heart rate patterns and other cardiovascular effects of nicotine delivered rapidly ( via nasal spray , NNS ) , slowly ( transdermal nicotine , TDN ) , by cigarette smoking ( rapid delivery of nicotine plus other smoke toxins ) , and placebo NNS .  Twelve healthy cigarette smokers were studied on a research ward when they smoked cigarettes ( 16 per day ) or used TDN ( 15 mg/16 h ) , NNS ( 24 1-mg doses per day ) , or placebo NNS , each for 5 days . There were no significant differences in systolic blood pressure , but diastolic blood pressure was slightly increased during cigarette smoking . Plasma epinephrine , & bgr;-thromboglobulin , and fibrinogen levels were higher during cigarette smoking than with TDN . For most measurements , NNS values were intermediate between and not significantly different from those of cigarette smoking and TDN . We conclude that , at recommended doses , TDN and NNS have fewer effects on biomarkers of cardiovascular risk than does cigarette smoking INTRODUCTION Tobacco smoking leads to changes in hemodynamic parameters such as heart rate and systolic or diastolic blood pressure . It has a direct influence on the elasticity of blood vessels and increases arterial stiffness , which can result in development of atherosclerosis . Data show that the nicotine in tobacco smoke probably is responsible for these changes . Electronic cigarettes ( e-cigarettes ) were supposedly a healthier alternative to combustible cigarettes because they imitate a process of cigarettes smoking but generate nicotine aerosol without the toxic substances from tobacco combustion . However , the use of e-cigarettes is still controversial because their toxicity , safety and long term use health impact have not been sufficiently studied . AIM The aim of this study was to evaluate changes in arterial stiffness parameters after smoking a cigarette or e-cigarette use . METHODS Fifteen healthy women , aged 19 - 25 years old , smoking ≥5 cigarettes per day for at least two years participated in the study . A non-invasive measurement of arterial stiffness parameters - Stiffness Index ( SI ) and Reflection Index ( RI ) - was conducted and systolic and diastolic blood pressure and heart rate were measured before and after smoking a conventional cigarette as well as use of an e-cigarette . RESULTS Statistically significant changes in the SI and RI were observed before and after smoking of a conventional cigarette [ SI : 6.75 m/s ( 6.66 - 6.85 , 95 % CI ) vs 6.56 m/s ( 6.46 - 6.65 . 95 % CI ) , p=0.0056 ; RI : 54.0 % ( 51.5 - 56.7 , 95 % CI ) vs 49.6 % ( 47.5 - 51.8 , 95 % CI ) , p=0.010 ] . The use of e-cigarettes result ed in no statistically significant changes in the SI and RI . After both product use systolic and diastolic blood pressure and heart rate increased but the changes were not statistically significant . CONCLUSIONS In contrast to conventional cigarette use , the use of electronic cigarettes causes no changes in arterial stiffness . This may indicate lower bioavailability of nicotine from the e-cigarette or an additional effect of other substances present in cigarette smoke but absent in an e-cigarette aerosol Background Electronic cigarettes ( e-cigarettes ) are becoming increasingly popular with smokers worldwide . Users report buying them to help quit smoking , to reduce cigarette consumption , to relieve tobacco withdrawal symptoms , and to continue having a ‘ smoking ’ experience , but with reduced health risks . Research on e-cigarettes is urgently needed in order to ensure that the decisions of regulators , healthcare providers and consumers are based on science . Methods ECLAT is a prospect i ve 12-month r and omized , controlled trial that evaluates  smoking reduction/abstinence  in 300 smokers not intending to quit experimenting two different nicotine strengths of a popular e-cigarette model ( ‘ Categoria ’ ; Arbi Group Srl , Italy ) compared to its non-nicotine choice . GroupA ( n = 100 ) received 7.2 mg nicotine cartridges for 12 weeks ; GroupB ( n = 100 ) , a 6-week 7.2 mg nicotine cartridges followed by a further 6-week 5.4 mg nicotine cartridges ; GroupC ( n = 100 ) received no-nicotine cartridges for 12 weeks . The study consisted of nine visits during which cig/day use and exhaled carbon monoxide ( eCO ) levels were measured . Smoking reduction and abstinence rates were calculated . Adverse events and product preferences were also review ed . Results Declines in cig/day use and eCO levels were observed at each study visits in all three study groups ( p<0.001 vs baseline ) , with no consistent differences among study groups . Smoking reduction was documented in 22.3 % and 10.3 % at week-12 and week-52 respectively . Complete abstinence from tobacco smoking was documented in 10.7 % and 8.7 % at week-12 and week-52 respectively . A substantial decrease in adverse events from baseline was observed and withdrawal symptoms were infrequently reported during the study . Participants ’ perception and acceptance of the product under investigation was satisfactory . Conclusion In smokers not intending to quit , the use of e-cigarettes , with or without nicotine , decreased cigarette consumption and elicited enduring tobacco abstinence without causing significant side effects . Trial Registration Clinical Trials.gov NCT01164072 Objective . To examine the effects of maternal prenatal smokeless tobacco use on infant birth size .  Design . A retrospective medical record review of 502 r and omly selected deliveries . Population and Setting . Singleton deliveries to Alaska Native women residing in a defined geographical region in western Alaska , 1997–2005 . Methods . A regional medical center 's electronic records were used to identify singleton deliveries . Data on maternal tobacco exposure and pregnancy outcomes were abstract ed from medical records . Logistic models were used to estimate adjusted mean birthweight , length and head circumference for deliveries to women who used no tobacco ( n=121 ) , used smokeless tobacco ( n=237 ) or smoked cigarettes ( n=59 ) . Differences in mean birthweight , length and head circumference , 95 % confidence intervals and p‐values were calculated using non‐users as the reference group . Main Outcome Measures . Infant birthweight , crown – heel length and head circumference . Results . After adjustment for gestational age and other potential confounders , the mean birthweight of infants of smokeless tobacco users was reduced by 78 g compared with that of infants of non‐users ( p=0.18 ) and by 331 g in infants of smokers ( p<0.01 ) . No association was found between maternal smokeless tobacco use and infant length or infant head circumference . Conclusions . We found a modest but non‐significant reduction in the birthweight of infants of smokeless tobacco users compared with infants of tobacco non‐users . Because smokeless tobacco contains many toxic compounds that could affect other pregnancy outcomes , results of this study should not be construed to mean that smokeless tobacco use is safe during pregnancy Objective To evaluate the safety and efficacy as a tool of smoking cessation of electronic cigarettes ( e-cigarettes ) , directly comparing users of e-cigarettes only , smokers of tobacco cigarettes only , and smokers of both . Design Prospect i ve cohort study . Final results are expected in 2019 , but given the urgency of data to support policies on electronic smoking , we report the results of the 12-month follow-up . Data Sources Direct contact and structured question naires by phone or via internet . Methods Adults ( 30–75 years ) were included if they were smokers of ≥1 tobacco cigarette/day ( tobacco smokers ) , users of any type of e-cigarettes , inhaling ≥50 puffs weekly ( e-smokers ) , or smokers of both tobacco and e-cigarettes ( dual smokers ) .  Carbon monoxide levels were tested in a sample of those declaring tobacco smoking abstinence . Main Outcome Measures Sustained smoking abstinence from tobacco smoking at 12 months , reduction in the number of tobacco cigarettes smoked daily . Data Synthesis We used linear and logistic regression , with region as cluster unit . Results Follow-up data were available for 236 e-smokers , 491 tobacco smokers , and 232 dual smokers ( overall response rate 70.8 % ) . All e-smokers were tobacco ex-smokers . At 12 months , 61.9 % of the e-smokers were still abstinent from tobacco smoking ; 20.6 % of the tobacco smokers and 22.0 % of the dual smokers achieved tobacco abstinence . Adjusting for potential confounders , tobacco smoking abstinence or cessation remained significantly more likely among e-smokers ( adjusted OR 5.19 ; 95 % CI : 3.35–8.02 ) , whereas adding e-cigarettes to tobacco smoking did not enhance the likelihood of quitting tobacco and did not reduce tobacco cigarette consumption . E-smokers showed a minimal but significantly higher increase in self-rated health than other smokers . Non significant differences were found in self-reported serious adverse events ( eleven overall ) . Conclusions Adding e-cigarettes to tobacco smoking did not facilitate smoking cessation or reduction . If e-cigarette safety will be confirmed , however , the use of e-cigarettes alone may facilitate quitters remaining so . Registration Number NCT01785537 We conducted a case-control study to test the hypothesis that women smokers who use oral contraceptives  have an increased risk of developing venous thrombosis .  Patients and controls were drawn from two sets of hospital patients already included in the Boston Collaborative Drug Surveillance Programme . Sixty patients with uncomplicated thromboembolism were matched with 180 controls with other diagnoses ; all were premenopausal women taking oral contraceptives . Patients with conditions that might predispose to thromboembolism or be related to smoking were excluded . We found no association between smoking habits and thromboembolism . Similarly , we found no association between thromboembolism , smoking , and duration of oral contraceptive use . Thus we conclude that differences in fibrinolytic activity between smokers and non-smokers are not major factors in the aetiology of uncomplicated thromboembolism in women using oral contraceptives Background Electronic cigarettes have been developed and marketed in recent years as smoking substitutes . However , no studies have evaluated their effects on the cardiovascular system . The purpose of this study was to examine the immediate effects of electronic cigarette use on left ventricular ( LV ) function , compared to the well-documented acute adverse effects of smoking . Methods Echocardiographic examinations were performed in 36 healthy heavy smokers ( SM , age 36 ± 5 years ) before and after smoking 1 cigarette and in 40 electronic cigarette users ( ECIG , age 35 ± 5 years ) before and after using the device with “ medium-strength ” nicotine concentration ( 11 mg/ml ) for 7 minutes . Mitral flow diastolic velocities ( E , A ) , their ratio ( E/A ) , deceleration time ( DT ) , isovolumetric relaxation time ( IVRT ) and corrected-to-heart rate IVRT ( IVRTc ) were measured . Mitral annulus systolic ( Sm ) , and diastolic ( Em , Am ) velocities were estimated . Myocardial performance index was calculated from Doppler flow ( MPI ) and tissue Doppler ( MPIt ) . Longitudinal deformation measurements of global strain ( GS ) , systolic ( SRs ) and diastolic ( SRe , SRa ) strain rate were also performed . Results Baseline measurements were similar in both groups . In SM , IVRT and IVRTc were prolonged , Em and SRe were decreased , and both MPI and MPIt were elevated after smoking . In ECIG , no differences were observed after device use . Comparing after-use measurements , ECIG had higher Em ( P = 0.032 ) and SRe ( P = 0.022 ) , and lower IVRTc ( P = 0.011 ) , MPI ( P = 0.001 ) and MPIt ( P = 0.019 ) . The observed differences were significant even after adjusting for changes in heart rate and blood pressure . Conclusions Although acute smoking causes a delay in myocardial relaxation , electronic cigarette use has no immediate effects . Electronic cigarettes ’ role in tobacco harm reduction should be studied intensively in order to determine whether switching to electronic cigarette use may have long-term beneficial effects on smokers ’ health . Trial registration Current Controlled Trials IS RCT OBJECTIVE We examined screening practice s and attitudes of obstetricians-gynecologists toward the use of noncombustible tobacco products ( chewing tobacco , snuff/snus , electronic cigarettes , and dissolvables )  during pregnancy . STUDY DESIGN The authors mailed a  survey in 2 
    Output:
    
We identified no evidence on CV outcomes among e-cigarette users using HC .
Limited data reporting mostly acute outcomes suggested that CV events are rare among e-cigarette users in the general population and that e-cigarettes may affect heart rate and blood pressure less than conventional cigarettes .