***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: 1 . Frei B , Engl and L , Ames BN . Ascorbate is an outst and ing antioxidant in human blood plasma . Proc Natl Acad Sci U S A 1989;86:6377–6381 . 2 . Ting HH , Timimi FK , Boles KS , Creager SJ , Ganz P , Creager MA . Vitamin C improves endothelium-dependent vasodilation in patients with non-insulindependent diabetes mellitus . J Clin Invest 1996;97:22–28 . 3 . Heitzer T , Just H , Munzel T. Antioxidant vitamin C improves endothelial dysfunction in chronic smokers . Circulation 1996;94:6–9 . 4 . Slakey D , Roza A , Pieper G , Johnson C , Adams M. Delayed cardiac allograft rejection due to combined cyclosporine and antioxidant therapy . Transplantation 1993;56:1305–1309 . 5 . Fish RD , Nabel EG , Selwyn AP , Ludmer PL , Mudge GH , Kirshenbaum JM , Schoen FJ , Alex and er RW , Ganz P. Responses of coronary arteries of cardiac transplant patients to acetylcholine . J Clin Invest 1988;81:21–31 . 6 . Davis SF , Yeung AC , Meredith IT , Charbonneau F , Ganz P , Selwyn AP , And erson TJ . Early endothelial dysfunction predicts the development of transplant coronary artery disease at 1 year posttransplant . Circulation 1996;93:457– 462 . 7 . Morrow JD , Roberts LJ II . Mass spectrometric quantification of F2-isoprostanes in biological fluids and tissues as measure of oxidant stress . Methods Enzymol 1999;300:3–12 . 8 . Watanabe H , Kakihana M , Ohtsuka S , Sugishita Y. R and omized , double-blind , placebo-controlled study of ascorbate on the preventive effect of nitrate tolerance in patients with congestive heart failure . Circulation 1998;97:886–891 CONTEXT Recent guidelines for treatment of overweight and obesity include recommendations for risk stratification by disease conditions and cardiovascular disease ( CVD ) risk factors , but the role of physical inactivity is not prominent in these recommendations . OBJECTIVE To quantify the influence of low cardiorespiratory fitness , an objective marker of physical inactivity , on CVD and all-cause mortality in normal-weight , overweight , and obese men and compare low fitness with other mortality predictors . DESIGN Prospect i ve observational data from the Aerobics Center Longitudinal Study . SETTING Preventive medicine clinic in Dallas , Tex . PARTICIPANTS A total of 25714 adult men ( average age , 43.8 years [ SD , 10.1 years ] ) who received a medical examination during 1970 to 1993 , with mortality follow-up to December 31 , 1994 . MAIN OUTCOME MEASURES Cardiovascular disease and all-cause mortality based on mortality predictors ( baseline CVD , type 2 diabetes mellitus , high serum cholesterol level , hypertension , current cigarette smoking , and low cardiorespiratory fitness ) stratified by body mass index . RESULTS During the study period , there were 1025 deaths ( 439 due to CVD ) during 258781 man-years of follow-up . Overweight and obese men with baseline CVD or CVD risk factors were at higher risk for all-cause and CVD mortality compared with normal-weight men without these predictors . Using normal-weight men without CVD as the referent , the strongest predictor of CVD death in obese men was baseline CVD ( age- and examination year-adjusted relative risk [ RR ] , 14.0 ; 95 % confidence interval [ CI ] , 9.4 - 20.8 ) ; RRs for obese men with diabetes mellitus , high cholesterol , hypertension , smoking , and low fitness were similar and ranged from 4.4 ( 95 % CI , 2.7 - 7.1 ) for smoking to 5.0 ( 95 % CI , 3.6 - 7.0 ) for low fitness . Relative risks for all-cause mortality in obese men ranged from 2.3 ( 95 % CI , 1.7 - 2.9 ) for men with hypertension to 4.7 ( 95 % CI , 3.6 - 6.1 ) for those with CVD at baseline . Relative risk for all-cause mortality in obese men with low fitness was 3.1 ( 95 % CI , 2.5 - 3.8 ) and in obese men with diabetes mellitus 3.1 ( 95 % CI , 2.3 - 4.2 ) and as slightly higher than the RRs for obese men who smoked or had high cholesterol levels . Low fitness was an independent predictor of mortality in all body mass index groups after adjustment for other mortality predictors . Approximately 50 % ( n = 1674 ) of obese men had low fitness , which led to a population -attributable risk of 39 % for CVD mortality and 44 % for all-cause mortality . Baseline CVD had population attributable risks of 51 % and 27 % for CVD and all-cause mortality , respectively . CONCLUSIONS In this analysis , low cardiorespiratory fitness was a strong and independent predictor of CVD and all-cause mortality and of comparable importance with that of diabetes mellitus and other CVD risk factors BACKGROUND The objective of this study was to examine the association of Joint National Committee ( JNC-V ) blood pressure and National Cholesterol Education Program ( NCEP ) cholesterol categories with coronary heart disease ( CHD ) risk , to incorporate them into coronary prediction algorithms , and to compare the discrimination properties of this approach with other noncategorical prediction functions . METHODS AND RESULTS This work was design ed as a prospect i ve , single-center study in the setting of a community-based cohort . The patients were 2489 men and 2856 women 30 to 74 years old at baseline with 12 years of follow-up . During the 12 years of follow-up , a total of 383 men and 227 women developed  CHD , which was significantly associated with categories of blood pressure , total cholesterol , LDL cholesterol , and HDL cholesterol ( all P<.001 ) . Sex-specific prediction equations were formulated to predict CHD risk according to age , diabetes , smoking , JNC-V blood pressure categories , and NCEP total cholesterol and LDL cholesterol categories . The accuracy of this categorical approach was found to be comparable to CHD prediction when the continuous variables themselves were used . After adjustment for other factors , approximately 28 % of CHD events in men and 29 % in women were attributable to blood pressure levels that exceeded high normal ( > or = 130/85 ) . The corresponding multivariable-adjusted attributable risk percent associated with elevated total cholesterol ( > or = 200 mg/dL ) was 27 % in men and 34 % in women . CONCLUSIONS Recommended guidelines of blood pressure , total cholesterol , and LDL cholesterol effectively predict CHD risk in a middle-aged white population sample . A simple coronary disease prediction algorithm was developed using categorical variables , which allows physicians to predict multivariate CHD risk in patients without overt CHD Data concerning the natural history of asymptomatic coronary artery disease ( CAD ) has been limited to epidemiologic rather than angiographic studies , thus leading to uncertainty as to whether warning symptoms and signs will identify subjects with silent myocardial ischemia before morbid events . To address this issue , 50 apparently healthy men with angiographically proven CAD and asymptomatic exercise-induced ST depression have been followed prospect ively for 15 years in the Oslo Ischemia Study . Fourteen men died . The initial presenting clinical event in these 14 men was chest pain in 4 (30%)--but in only 1 case was it recognized as typical angina -- silent myocardial infa rct ion in 5 ( 35 % ) and sudden death in 5 ( 35 % ) . Thirty-six men survived , with 19 developing symptoms . Overall , chest pain was the first clinical event in 22 of the total of 33 men with symptoms ( 66 % ) , whereas myocardial infa rct ion occurred in 6 ( 18 % ) and sudden death in 5 ( 16 % ) . Although chest pain occurred in 22 men , it was clinical ly diagnosed as typical angina pectoris in only 6 . These observations suggest that there is an absence of clear-cut ischemic symptoms in many asymptomatic patients before morbid events There is universal agreement [ 1 - 4 ] that women 50 to 69 years of age should undergo  screening mammography  because r and omized , controlled trials have shown that such screening reduces breast cancer mortality in this age group [ 5 , 6 ] . This consensus is bolstered by the results of cost-effectiveness analyses that consistently show that this benefit can be achieved at a reasonable cost [ 7 - 9 ] . In contrast , whether women 40 to 49 years of age should undergo screening mammography is controversial [ 10 - 15 ] . Pooled results of large r and omized , controlled trials have shown no mortality reduction in 40- to 49-year-old women after 7 to 9 years of screening [ 5 , 16 - 18 ] . However , a statistically significant reduction in breast cancer mortality becomes apparent 10 to 14 years after the initiation of screening [ 19 ] . Some authors have argued that this delayed benefit should not be ignored [ 11 ] . However , the reality of constrained health care re sources requires that any benefit from preventive services be achieved at a reasonable cost . Two recently published analyses [ 20 , 21 ] suggest that mammographic screening in younger women may be as cost-effective as screening in older women . The first analysis [ 20 ] calculated average cost-effectiveness by comparing a strategy of screening  40- to 69-year-old women with no screening . Most of the benefit achieved by using this strategy occurs when women are 50 to 69 years of age . Therefore , this analysis did not address whether it is cost-effective to screen women from 40 to 49 years of age in addition to screening them from 50 to 69 years of age . To determine whether the additional benefit obtained by extending screening mammography to women 40 to 49 years of age comes at a reasonable cost would require an incremental cost-effectiveness analysis [ 22 - 26 ] . The second analysis [ 21 ] used a simplified life-expectancy accounting method , did not discount costs or benefits , and associated screening mammography with unsubstantiated mortality reductions ( 30 % for the base case ) . Neither analysis [ 20 , 21 ] included an important aspect of the results of screening mammography trials in 40- to 49-year-old women : that is , no benefit occurs until 10 years after the initiation of screening . An earlier analysis [ 10 ] found screening mammography to be more expensive in women 40 to 49 years of age than in women 50 years of age and older . This previous analysis calculated incremental cost-effectiveness , discounted costs and benefits , and included an estimated delay between the onset of screening and the onset of a mortality benefit . Our analysis extends this work by including up date d pooled results of the r and omized , controlled trials [ 19 ] ; actual delay times before the onset of benefits ; and up date d costs of mammography and treatment of breast cancer . Methods Model We developed a Markov model [ 27 , 28 ] that compared the life expectancy of women undergoing different breast cancer screening strategies . Except for women in whom breast cancer was diagnosed at the initiation of screening , women were healthy at entry into the model . At the end of each 1-year cycle , women were in one of four health states : They remained healthy , developed breast cancer and remained alive , died of breast cancer , or died of another cause . The transition probabilities [ that is , the probabilities of developing breast cancer , dying of breast cancer , and dying of another cause ] were both age- and strategy -dependent . The base-case analysis compared three strategies : 1 ) no screening ; 2 ) screening biennially from 50 to 69 years of age ; and 3 ) screening every 18 months from 40 to 49 years of age , followed by screening biennially from 50 to 69 years of age . The rationale for these screening intervals is discussed below . We calculated the cost-effectiveness of screening in women 50 years of age and older by comparing the first strategy with the second strategy . To determine the incremental cost-effectiveness of screening in 40- to 49-year-old women , we compared the second and third strategies . Costs and benefits were discounted at a rate of 3 % per year for the base-case analysis [ 23 ] . Benefits Trials of screening mammography have shown no reduction in breast cancer mortality among screened women until several years after the initiation of screening [ 5 , 18 , 29 , 30 ] . Meta-analyses and one pooled analysis have shown that among 40- to 49-year-old women , the summary relative risk reduction in breast cancer mortality 7 to 9 years after the initiation of screening is about 1 , indicating no reduction in mortality [ 5 , 16 - 
    Output:
    
The Task Force found insufficient evidence to recommend for or against using these tests to screen middle-aged and older men and women .
They recommended against screening children , adolescents , or young adults .
No effect was seen among men with a normal baseline result on exercise tolerance testing .
It is not clear from the report of this post hoc analysis whether the cardiovascular risk profiles of participants with an abnormal result on exercise tolerance testing  at baseline differed significantly from those of participants with a normal result .