***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: BACKGROUND Older age is a risk factor for higher mortality after acute myocardial infa rct ion ( AMI ) , but the association with health status outcomes is largely unexplored . METHODS In a prospect i ve cohort of 2498 patients in the PREMIER study , we compared health-related quality of life ( HRQL ) and burden of angina symptoms among survivors of AMI by age strata ( age groups > or = 75 , 65 - 74 , 50 - 64 , and 19 - 49 years ) using the Seattle Angina Question naire . Multivariable analyses assessed the relationship between age and 1-year HRQL and angina burden , adjusting for differences in clinical characteristics , treatment , and baseline health status . RESULTS Older patients comprised a majority : 20.1 % were > or = 75 years of age , 41.7 % were 65 to 74 years of age , 20.7 % were 50 to 64 years of age , and 17.4 % were < 50 years of age . At 12 months , older patients had higher mortality ( 17.0 % vs 8.7 % vs 6.1 % vs 3.2 % for age groups > or = 75 , 65 - 74 , 50 - 64 , 19 - 49 ; P < .001 ) . Among survivors of AMI , increasing age was associated with less angina and better HRQL . By 12 months , older patients reported less angina ( 10.9 % vs 12.7 % vs 19.3 % vs 23.4 % for age groups > or = 75 , 65 - 74 , 50 - 64 , 19 - 49 ; P < .0001 ) and better HRQL ( scores 89.1 vs 88.1 vs 82.5 vs 80.0 , respectively ; P < .0001 ) , which persisted after adjustment for baseline angina , HRQL , and other demographic , clinical , disease severity , and treatment differences . CONCLUSIONS Although older patients have higher mortality after AMI , those who survive experience fewer symptoms and better HRQL at 1 year than younger patients . Angina remains present in a number of patients across the spectrum of age , supporting strategies to systematic ally assess and treat symptoms after AMI Background — Although numerous studies have reported that cardiac rehabilitation ( CR ) is associated with reduced mortality after myocardial infa rct ion , less is known about its association with mortality after percutaneous coronary intervention . Methods and Results — We performed a retrospective analysis of data from a prospect ively collected registry of 2395 consecutive patients who underwent percutaneous coronary intervention in Olmsted County , Minnesota , from 1994 to 2008 . The association of CR with all-cause mortality , cardiac mortality , myocardial infa rct ion , or revascularization was assessed with 3 statistical techniques : propensity score – matched analysis ( n=1438 ) , propensity score stratification ( n=2351 ) , and regression adjustment with propensity score in a 3-month l and mark analysis ( n=2009 ) . During a median follow-up of 6.3 years , 503 deaths ( 199 cardiac ) , 394 myocardial infa rct ions , and 755 revascularization procedures occurred in the study subjects . Participation in CR , noted in 40 % ( 964 of 2395 ) of the cohort , was associated with a significant decrease in all-cause mortality by all 3 statistical techniques ( hazard ratio , 0.53 to 0.55 ; P<0.001 ) . A trend toward decreased cardiac mortality was also observed in CR participants ; however , no effect was observed for subsequent myocardial infa rct ion or revascularization . The association between CR participation and reduced mortality rates was similar for men and women , for older and younger patients , and for patients undergoing elective or nonelective percutaneous coronary intervention . Conclusions — We found that CR participation after percutaneous coronary intervention was associated with a significant reduction in mortality rates . These findings add support to published clinical practice guidelines , performance measures , and insurance coverage policies that recommend CR for patients after percutaneous coronary intervention AIMS We investigated the net benefit in the outcome of reducing treatment delay through field triage and emergency department ( ED ) bypass in patients with ST-elevation myocardial infa rct ion ( STEMI ) treated with primary angioplasty .  METHODS AND RESULTS In a prospect i ve registry study , consecutive patients with suspected STEMI were assigned to : ( i ) pre-hospital ECG and triage or ( ii ) ECG and triage at the closest ED , solely based on ambulance availability . Four district hospitals and one regional heart centre serviced the 890,000 population metropolitan area and primary angioplasty was the only reperfusion strategy employed . Baseline characteristics were similar in STEMI patients triaged in the field ( 108 ) and the EDs ( 193 ) . Symptom onset to balloon times : 154 [ inter-quartile range ( IQR ) 120 - 233 ) vs. 249 ( IQR 184 - 405 ) min ( P<0.001 ) and peak creatine kinase in early presenters ( < 2 h ) : 1435 ( 95 % CI : 904 - 1966 ) U/L vs. 2320 ( 95 % CI : 1881 - 2762 ) U/L ( P=0.009 ) were lower in field- than in ED-triaged patients . Mortality in the PCI treated were 1.1 and 8.2 % [ P=0.025 , RR 0.14 ( 95 % CI : 0.01 - 1.08 ) ] and overall mortality were 1.9 and 7.3 % [ P=0.046 , RR 0.26 ( 95 % CI : 0.05 - 1.11 ) ] . CONCLUSION Field-triage and ED bypass were feasible means of reducing treatment delay in patients with suspected STEMI and result ed in smaller infa rct size in early presenters and a trend towards a reduction in mortality Background Prospect i ve r and omized trials comparing the coronary artery disease-related health status outcomes ( changes in symptom grade , physical functional capacity and health-related quality of life ) after  percutaneous coronary intervention  at hospitals with and without on-site cardiac surgical backup have not been reported earlier . Methods We r and omly assigned 609 consecutive patients fulfilling pre-specified procedural low-risk criteria to undergo percutaneous coronary intervention at either a community hospital without or a regional hospital with on-site surgical backup . Five hundred and seventy-six patients completed the health status evaluation at baseline and at 6 months follow-up . Results At baseline , 91.4 % had symptoms , and the mean ( st and ard deviation ) Canadian Cardiovascular Society 's classification was 2.5 ( 0.9 ) . The procedural success rates and the changes in health status measures were similar at the two hospitals . Overall there was a substantial relief of symptoms with a reduction in Canadian Cardiovascular Society 's classification of 1.9 ( 1.2 ) , increase in exercise time [ 1.4 ( 1.9 ) min ] and reduction in use of antianginal drugs [ 0.6 ( 0.9 ) less drugs ] at follow-up compared with baseline ( all P > 0.001 ) . Health-related quality of life was evaluated with the Short-Form 36 health survey . There were significant and similar improvements in nearly all multi-item and summary scores from baseline to follow-up at the two hospitals . The largest improvements were seen in items related to physical functioning [ overall change in Physical Component Score from baseline to follow-up 6.9 ( 9.1 ) points , P > 0.001 ] and lowest in the mental health domains [ change in Mental Component Score 3.3 ( 10.7 ) points , P > 0.001 ] . Interpretation This study shows that a substantial and comparable gain in coronary artery disease-related health status can be achieved at hospitals both with and without surgical backup Background —Improving patients ’  quality of life is a primary indication for percutaneous coronary intervention ( PCI ) , yet little is known about patient characteristics associated with greater quality -of-life improvement from the procedure . This study was conducted to identify patient characteristics associated with quality -of-life benefit after PCI . Methods and Results —A consecutive series of 1518 patients undergoing PCI in nonacute myocardial infa rct ion setting s were prospect ively enrolled into an observational study documenting their postprocedural health status . We examined univariate and multivariable associations between baseline patient characteristics and quality of life 1 year after the procedure using the disease-specific Seattle Angina Question naire ( SAQ ) to quantify the impact of patients ’ coronary disease on their quality of life . Baseline angina frequency and physical function were the strongest predictors of quality -of-life improvement 1 year after PCI . In comparing patients without angina to those experiencing monthly , weekly , and daily angina , the quality -of-life improvements ( mean±SEM ) were 21.4±2.1 , 30.7±2.2 , and 34.6±2.6 points greater ( P<0.001 ) . Patients with mild , moderate , and severe physical limitation improved 13.8±1.9 , 20.0±2.1 , and 13.5±3.5 points more than those with minimal baseline physical limitation ( P<0.001 ) . These findings were maintained in multivariable models correcting for baseline differences in demographic , clinical , disease-severity , and health-status variables . Conclusions —Preprocedural angina frequency is the most important prognostic indicator of quality -of-life improvement  after PCI . Although substantial quality -of-life benefits are attained in most patients with preprocedural angina , more careful consideration of the potential benefits and risks of the procedure are needed in asymptomatic patients overground and treadmill walking . J Biomech Eng 2001 ; 123 : 27–32 . 10 . ElHaber N , Hill KD , Cassano AT et al. Genetic and environmental influences on variation in balance performance among female twin pairs aged 21–82 years . Am J Epidem 2006 ; 164 : 246–56 . 11 . Besser MP , Kmieczak K , Schwartz L , Snyderman M , Wasko J , Selby-Silverstein L. Representation of temporal spatial gait parameters using means in adults without impairment . Gait Posture 1999 ; 9 : 113 . 12 . Lindemann U , Najafi B , Zijlstra W , Hauer K , Muche R , Becker C et al. Distance to achieve steady state walking speed in frail elderly persons . Gait Posture 2008 ; 27 : 91–6 . 13 . Paterson KL , Hill KD , Lythgo ND , Maschette W. The reliability of spatiotemporal gait data for young and older women during continuous overground walking . Arch Phys Med Rehabil 2008 ; 89 : 2360–5 . 14 . Selby-Silverstein L , Besser MP . Accuracy of the GAITRite system for measuring temporal-spatial parameters of gait . Presented at : American Physical Therapy Association Combined Annual Conference ; 7 June 1999 ; Washington , D.C. 15 . Atkinson G , Nevill AM . Statistical methods for assessing measurement error ( reliability ) in variables relevant to sports medicine . Sports Med 1998 ; 26 : 217–38 . 16 . Perneger TV . What ’s wrong with Bonferroni adjustments . BMJ 1998 ; 316 : 1236–8 . 17 . Portney LG , Watkins MP . Foundations of Clinical Research : Applications to Practice , 2nd edition . Upper Saddle River , NJ : Prentice Hall Health , 2000 . 18 . Cohen J. Statistical Power Analysis for the Behavioral Sciences , 2nd edition . Hillsdale , NJ : Lawrence Erlbaum Associates , 1988 . 19 . Orendurff MS , Schoen JA , Bernatz GC , Segal AD , Klute GK . How humans walk : bout duration , steps per bout , and rest duration . J Rehabil Res Dev 2008 ; 45 : 1077–90 . 20 . Griffin L , West DJ , West BJ . R and om stride intervals with memory . J Biol Phys 2000 ; 26 : 185–202 . 21 . Hausdorff JM , Purdon PL , Peng CK , Ladin Z , Wei JY , Goldberger AL . Fractal dynamics of human gait : stability of long-range correlations in stride interval fluctuations . J App Physiol 1996 ; 80 : 1448–57 . 22 . Besser MP , Selby-Silverstein L , Prickett N. Predicting fall risk  in the elderly using temporal-spatial parameters of gait . Neurol Rep 2001 ; 25 : S3 This study was performed to assess the possibility that patient age may independently affect improvements in health-related quality of life following percutaneous coronary intervention .  One hundred five patients undergoing elective percutaneous coronary intervention at a single tertiary referral center between January 10 , 2001 and January 6 , 2002 were enrolled and prospect ively evaluated . Health-related quality of life was assessed before and 1 year following percutaneous coronary intervention 
    Output:
    
Findings revealed that everyone regardless of age reported better health-related quality of life , primarily from the relief of angina and improved physical and mental function .
Age itself did not have an independent predictive effect when other factors such as comorbid conditions were taken into account .