***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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    ***EXAMPLES*** 
    Input: Aims Atrial fibrillation ( AF ) is associated with adverse outcome . Whether recently discovered genetic risk markers improve AF risk prediction is unknown . Methods and results We derived and vali date d a novel AF risk prediction model from 32 possible predictors in the Women 's Health Study ( WHS ) , a cohort of 20 822 women without cardiovascular disease ( CVD ) at baseline followed prospect ively for incident AF ( median : 14.5 years ) . We then created a genetic risk score ( GRS ) comprised of 12 risk alleles in nine loci and assessed model performance in the validation cohort with and without the GRS . The newly derived WHS AF risk algorithm included terms for age , weight , height , systolic blood pressure , alcohol use , and smoking ( current and past ) . In the validation cohort , this model was well calibrated with good discrimination [ C-index ( 95 % CI ) = 0.718 ( 0.684–0.753 ) ] and improved all reclassification indices when compared with age alone . The addition of the genetic score to the WHS AF risk algorithm model improved the C-index [ 0.741 ( 0.709–0.774 ) ; P = 0.001 ] , the category-less net reclassification [ 0.490 ( 0.301–0.670 ) ; P < 0.0001 ] , and the integrated discrimination improvement [ 0.00526 ( 0.0033–0.0076 ) ; P < 0.0001 ] . However , there was no improvement in net reclassification into 10-year risk categories of < 1 , 1–5 , and 5+% [ 0.041 ( −0.044–0.12 ) ; P = 0.33 ] . Conclusion Among women without CVD , a simple risk prediction model utilizing readily available risk markers identified women at higher risk for AF . The addition of genetic information result ed in modest improvements in predictive accuracy that did not translate into improved reclassification into discrete AF risk categories BACKGROUND Cigarette smoking increases the risk of coronary heart disease , but whether smoking increases atrial fibrillation ( AF ) is uncertain . OBJECTIVE The purpose of this study was to determine the association of cigarette smoking with incident AF in a population -based cohort of blacks and whites . METHODS We determined the risk of incident AF through December 2002 in relation to baseline ( 1987 - 1989 ) smoking status and cigarette-years of smoking in over 15,000 participants of the prospect i ve Atherosclerosis Risk in Communities ( ARIC ) study . RESULTS Over a mean follow-up of 13.1 years , 876 incident AF events were identified . Compared to never smokers , the multivariable-adjusted hazard ratios ( HRs ) for AF were 1.32 ( 95 % confidence interval [ CI ] 1.10 - 1.57 ) in former smokers , 2.05 ( 95 % CI 1.71 - 2.47 ) in current smokers , and 1.58 ( 95 % CI 1.35 - 1.85 ) in ever smokers . In the highest tertile of accumulated smoking amount ( > 675 cigarette-years ) , the incidence of AF was 2.10 times greater ( 95 % CI 1.74 - 2.53 ) than in those who never smoked . Associations were similar by gender , race , type of event ( AF and atrial flutter ) , and when only AF events identified by study exam ECGs were included . Finally , individuals who quit smoking exhibited a trend indicating a slightly lower risk of developing AF ( HR 0.88 , 95 % CI 0.65 - 1.17 ) compared to those who continued to smoke . CONCLUSION Smoking was associated with the incidence of AF , with more than a two-fold increased risk of AF attributed to current smoking . In addition , a trend toward a lower incidence of AF appeared among smokers who quit compared to continued smokers BACKGROUND Cigarette smoking is a known risk factor for cardiovascular disease ( CVD ) , but its relationship to the development of hypertension is unclear . Previous epidemiological studies have shown inconsistent results , having demonstrated inverse and positive associations between cigarette smoking and the development of hypertension . METHODS We analyzed 13,529 male participants from the Physicians ' Health Study free of baseline hypertension and CVD who provided information about smoking status . Smoking status was categorized as never , past , or current < 20 cigarettes/day , or current > or = 20 cigarettes/day .  Incident hypertension was defined as either the initiation of antihypertensive treatment , self-reported systolic blood pressure ( BP ) > or = 140 mm Hg , or diastolic BP > or = 90 mm Hg . RESULTS Over a median follow-up of 14.5 years , 4,904 men developed hypertension .  We modeled the risk of developing hypertension by baseline smoking status adjusting for known risk factors for hypertension or CVD . In a fully adjusted Cox proportional hazards model , we found that compared with never smokers , past smokers and current smokers had corresponding relative risks ( RRs ) of 1.08 and 1.15 of developing hypertension . The risk for smokers did not appear to differ based on number of cigarettes smoked daily . Further , the RR of hypertension was higher for men with normal vs. prehypertensive levels of systolic ( SBP ) or diastolic BP ( DBP ) . CONCLUSIONS This prospect i ve cohort data suggests that cigarette smoking may be a modest but important risk factor for the development of hypertension The validity of atrial fibrillation ( AF ) diagnoses in national registers for use as endpoints in prospect i ve studies has not been evaluated . We studied the validity of AF diagnoses in Swedish national hospital discharge and cause of death registers and the occurrence of and risk factors for AF in a middle-aged Swedish population using these registers . Our study included the 30,447 individuals ( age 44–73 ) who attended baseline visits in 1991–1996 of the Malmö Diet and Cancer study . Individuals with a first AF diagnosis were identified by record linkage with national registers . A subset of cases was r and omly selected for validation by examination of electrocardiograms and patient records . Electrocardiograms were available in 98 % of the validation sample ( 95 % definitive AF , 3 % no AF ) . The 2 % with ECGs unavailable had probable AF . Baseline AF prevalence was 1.3 % , higher in men and increased with age . During 11.2 years of follow-up 1430 first AF diagnoses occurred . Risk factors were age , hypertension , BMI , diabetes , history of heart failure , history of myocardial infa rct ion and , in men but not women , current smoking . The strongest risk factors were history of heart failure ( hazard ratio men 4.5 , women 8.7 ) and myocardial infa rct ion ( hazard ratio men 2.0 , women 1.8 ) . The largest population attributable risks were observed for hypertension ( men 38 % , women 34 % ) and obesity ( men 11 % , women 10 % ) . In conclusion , case misclassification of AF in national registers is small , indicating feasibility of use in prospect i ve studies . Hypertension and obesity account for large portions of population risk in middle-aged individuals with low prevalence of manifest cardiac disease Atrial fibrillation ( AF ) is the most frequently encountered cardiac arrhythmia . It is a risk factor for stroke and premature death . We studied the temporal changes in the prevalence of  AF  from 1976 to 1994 in a r and om population aged 50 to 89 years . The prevalence of AF , diagnosed from electrocardiograms ( ECGs ) , was determined in 8,606 patients examined in 1976 to 1978 , in 8,943 patients examined in 1981 to 1983 , and in 6,733 subjects examined in 1991 to 1994 . Changes in prevalence of AF were estimated by logistic regression analysis . In men , the age-st and ardized prevalence of AF increased from 1.4 % in 1976 to 1978 ( odds ratio [ OR ] 1.0 , reference ) to 1.9 % in 1981 to 1983 ( OR 1.6 , 95 % confidence interval [ CI ] 1.1 to 2.1 ) , and to 3.3 % in 1991 to 1994 ( OR 2.3 , 95 % CI 1.6 to 3.4 , p<0.001 , adjusted for age ) . In women , the prevalence of AF decreased from 1.5 % in 1976 to 1978 ( OR 1.0 , reference ) to 1.0 % in 1981 to 1983 ( OR 0.7 , 95 % CI 0.5 to 1.0 ) , and to 1.1 % in 1991 to 1994 ( OR 0.7 , 95 % CI 0.5 to 1.0 ) , although the overall decrease was not significant ( p=0.11 , adjusted for age ) . After adjusting for changes in comorbidity , body weight , and height , the increase in the prevalence of AF in men from 1976 to 1978 and from 1991 to 1994 remained significant ( OR 1.9 , 95 % CI 1.3 to 2.8 , p=0.002 ) . Although unchanged in women , the prevalence of AF in men more than doubled from the 1970s to the 1990s . The factors responsible for this gender-specific increase in the prevalence of this common arrhythmia have yet to be identified BACKGROUND An atrial fibrillation ( AF ) risk score for a non-Western general population has not been established . Methods and Results : A total of 6,898 participants ( 30 - 79 years old ) initially free of AF have been prospect ively followed for incident AF since 1989 . AF was diagnosed when AF or atrial flutter was present on ECG at a biannual health examination ; was indicated as a current illness ; or was in the medical records during follow-up . Cox proportional hazard ratios were analyzed after adjusting for cardiovascular risk factors at baseline . During the 95,180 person-years of follow-up , 311 incident AF events occurred . We developed a scoring system for each risk factor as follows : 0/-5 , 3/0 , 7/5 , and 9/9 points for men/women in their 30 s-40 s , 50 s , 60 s , and 70 s , respectively ; 2 points for systolic hypertension , overweight , excessive drinking , or coronary artery disease ; 1 point for current smoking ; -1 point for moderate non-high-density lipoprotein-cholesterol ; 4 points for arrhythmia ; and 8 , 6 , and 2 points for subjects with cardiac murmur in their 30 s-40 s , 50 s , and 60 s , respectively ( C-statistic 0.749 ; 95 % confidence interval , 0.724 - 0.774 ) . Individuals with score ≤2 , 10 - 11 , or ≥16 points had , respectively , ≤1 % , 9 % , and 27 % observed probability of developing AF in 10 years . CONCLUSIONS We developed a 10-year risk score for incident AF using traditional risk factors that are easily obtained in routine outpatient clinics/health examinations without ECG Background Identification of individuals at risk for developing atrial fibrillation ( AF ) will help to target screening and preventive interventions . We aim ed to vali date the CHARGE-AF model ( including variables age , race , height , weight , blood pressure , smoking , antihypertensive medication , diabetes , myocardial infa rct ion and heart failure ) for prediction of five-year incident AF in a representative European population with a wide age range . Methods and results The CHARGE-AF model was calculated in 24,020 participants of the population -based EPIC Norfolk study with 236 cases of hospitalization with diagnosis of AF within five years . The model showed good discrimination ( c-statistic 0.81 , 95 % confidence interval ( CI ) 0.75–0.85 ) , but weak calibration ( Chi2-statistic 142 ) with an almost two-fold overestimation of AF incidence . A recalibration to characteristics of the European Prospect i ve Investigation into Cancer and Nutrition ( EPIC ) Norfolk cohort improved calibration considerably ( Chi2-statistic 13.3 ) , with acceptable discrimination in participants both > 65 and ≤65 years of age ( c-statistics 0.70 , 95 % CI 0.61–0.77 and 0.83 , 95 % CI 0.74–0.88 ) . The recalibrated model also showed good discrimination in participants free of cardiovascular disease ( c-statistics 0.80 , 95 % CI 0.75–0.84 ) . Categories of predicted risk ( < 2.5 % , 2.5–5 % or > 5 % ) showed good concordance with observed five-year AF incidence of 0.62 % , 3.49 % and 8.74 % ( log rank test p < 0.001 ) , respectively . Conclusion A recalibration of the CHARGE-AF model is 
    Output:
    
Conclusions The current meta- analysis suggests that smoking is associated with an increased risk of atrial fibrillation in a dose-dependent matter , but the association is weaker among former smokers compared to current smokers