***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 and Purpose — The role of physical activity , especially that of occupational and commuting physical activity , in the prediction of stroke risk is not properly established . We assessed the relationship of different types of physical activity with total and type-specific stroke risk . Methods — We prospect ively followed 47 721 Finnish subjects 25 to 64 years of age without a history of coronary heart disease , stroke , or cancer at baseline .  Hazard ratios ( HRs ) for incident stroke were estimated for different levels of leisure time , occupational , and commuting physical activity . Results — During a mean follow-up of 19.0 years , 2863 incident stroke events were ascertained . The multivariate-adjusted ( age , sex , area , study year , body mass index , systolic blood pressure , cholesterol , education , smoking , alcohol consumption , diabetes , and other 2 types of physical activity ) HRs associated with low , moderate , and high leisure time physical activity were 1.00 , 0.86 , and 0.74 ( Ptrend<0.001 ) for total stroke , 1.00 , 0.87 , and 0.46 ( Ptrend=0.011 ) for subarachnoid hemorrhage , 1.00 , 0.77 , and 0.63 ( Ptrend=0.024 ) for intracerebral hemorrhage , and 1.00 , 0.87 , and 0.80 ( Ptrend=0.001 ) for ischemic stroke , respectively . The multivariate-adjusted HRs associated with none , 1 to 29 , and ≥30 minutes of active commuting were 1.00 , 0.92 , and 0.89 ( Ptrend=0.043 ) for total stroke , and 1.00 , 0.93 , and 0.86 ( Ptrend=0.028 ) for ischemic stroke , respectively . Occupational activity had a modest association with ischemic stroke in the multivariate analysis ( Ptrend=0.046 ) . Conclusion — A high level of leisure time physical activity  reduces the risk of all subtypes of stroke . Daily active commuting also reduces the risk of ischemic stroke CONTEXT Women who are  physically active  have a decreased risk for breast cancer , but the types , amounts , and timing of activity needed are unknown . OBJECTIVE To prospect ively examine the association between current and past recreational physical activity and incidence of  breast cancer in postmenopausal women . DESIGN , SETTING , AND PATIENTS Prospect i ve cohort study in 74 171 women aged 50 to 79 years who were recruited by 40 US clinical centers from 1993 through 1998 . MAIN OUTCOME MEASURE Incident invasive and in situ breast cancer . RESULTS We documented 1780 newly diagnosed cases of breast cancer over a mean follow-up of 4.7 years . Compared with less active women , women who engaged in regular strenuous physical activity at age 35 years had a 14 % decreased risk of breast cancer ( relative risk [ RR ] , 0.86 ; 95 % confidence interval [ CI ] , 0.78 - 0.95 ) . Similar but attenuated findings were observed for strenuous physical activity at ages 18 years and 50 years . An increasing total current physical activity score was associated with a reduced risk for breast cancer ( P = .03 for trend ) . Women who engaged in the equivalent of 1.25 to 2.5 hours per week of brisk walking had an 18 % decreased risk of breast cancer ( RR , 0.82 ; 95 % CI , 0.68 - 0.97 ) compared with inactive women . Slightly greater reduction in risk was observed for women who engaged in the equivalent of 10 hours or more per week of brisk walking . The effect of exercise  was most pronounced in women in the lowest tertile of body mass index ( BMI ) ( < 24.1 ) , but also was observed for women in the middle tertile of BMI ( 24.1 - 28.4 ) . CONCLUSIONS These data suggest that increased physical activity is associated with reduced risk for breast cancer in postmenopausal women , longer duration provides most benefit , and that such activity need not be strenuous CONTEXT Depressive symptoms predict adverse cardiovascular outcomes in patients with coronary heart disease , but the mechanisms responsible for this association are unknown . OBJECTIVE To determine why depressive symptoms are associated with an increased risk of cardiovascular events . DESIGN AND PARTICIPANTS The Heart and Soul Study is a prospect i ve cohort study of 1017 out patients with stable coronary heart disease followed up for a mean ( SD ) of 4.8 ( 1.4 ) years . SETTING Participants were recruited between September 11 , 2000 , and December 20 , 2002 , from 12 outpatient clinics in the San Francisco Bay Area and were followed up to January 12 , 2008 . MAIN OUTCOME MEASURES Baseline depressive symptoms were assessed using the Patient Health Question naire ( PHQ ) . We used proportional hazards models to evaluate the extent to which the association of depressive symptoms with subsequent cardiovascular events ( heart failure , myocardial infa rct ion , stroke , transient ischemic attack , or death ) was explained by baseline disease severity and potential biological or behavioral mediators . RESULTS A total of 341 cardiovascular events occurred during 4876 person-years of follow-up . The age-adjusted annual rate of cardiovascular events was 10.0 % among the 199 participants with depressive symptoms ( PHQ score > or = 10 ) and 6.7 % among the 818 participants without depressive symptoms ( hazard ratio [ HR ] , 1.50 ; 95 % confidence interval , [ CI ] , 1.16 - 1.95 ; P = .002 ) . After adjustment for comorbid conditions and disease severity , depressive symptoms were associated with a 31 % higher rate of cardiovascular events ( HR , 1.31 ; 95 % CI , 1.00 - 1.71 ; P = .04 ) . Additional adjustment for potential biological mediators attenuated this association ( HR , 1.24 ; 95 % CI , 0.94 - 1.63 ; P = .12 ) . After further adjustment for potential behavioral mediators , including physical inactivity , there was no significant association ( HR , 1.05 ; 95 % CI , 0.79 - 1.40 ; P = .75 ) . CONCLUSION In this sample of out patients with coronary heart disease , the association between depressive symptoms and adverse cardiovascular events was largely explained by behavioral factors , particularly physical inactivity OBJECTIVE We sought to evaluate factors that are associated with physical activity changes among adults within a 5-year period . METHODS From May 2001 to December 2002 we r and omly enrolled 1514 men and 1528 women without any evidence of cardiovascular or any other chronic disease . The sampling was stratified by the age-gender distribution of the greater area of Athens .  Weekly energy expenditure assessed by considering frequency , duration , and intensity of sports-related physical activity .  During 2006 , the 5-year follow-up was performed in 1955 participants , which included , among others , current physical activity status . RESULTS A total of 587 ( 61 % ) men and 673 ( 68 % ) women were classified as physically inactive at baseline , whereas 661 ( 69 % ) men and 728 ( 73 % ) women were classified as physically inactive at follow-up ; thus , a 13 % increase in physical inactivity rate was observed in men and a 7 % in women during the follow-up period ( p < 0.01 ) . Multivariate analysis revealed that male gender , being a nonsmoker , healthy eating , better self-reported quality -of-life , and lower prevalence of hypercholesterolemia and incidence of cardiovascular disease were the characteristics of people that remained physically active ; advanced age , anxiety and depression , overweight , and low quality -of-life were the baseline predictors of physical inactivity among initially active participants , which also had a greater incidence of cardiovascular disease . CONCLUSIONS Gender , aging , psychological disorders , body mass , smoking , dietary habits , perceived health status , and quality -of-life were the most important discriminating factors of physical activity changes BACKGROUND The prevention of disability in activities of daily living ( ADL ) may prolong older persons ' autonomy ( older persons are defined in this study as those aged > or = 60 years ) . However , proved preventive strategies for ADL disability are lacking . A sedentary lifestyle is an important cause of disability . This study examines whether an exercise program can prevent ADL disability . METHODS A 2-center , r and omized , single-blind , controlled trial was conducted in which participants were assigned to an aerobic exercise program , a resistance exercise program , or an attention control group .  Of the 439 community-dwelling persons aged 60 years or older with knee osteoarthritis originally recruited , the 250 participants initially free of ADL disability were used for this study .  Incident ADL disability , defined as developing difficulty in transferring from a bed to a chair , eating , dressing , using the toilet , or bathing , was assessed quarterly during 18 months of follow-up . RESULTS The cumulative incidence of ADL disability was lower in the exercise groups ( 37.1 % ) than in the attention control group ( 52.5 % ) ( P = .02 ) . After adjustment for demographics and baseline physical function , the relative risk of incident ADL disability for assignment to exercise was 0.57 ( 95 % confidence interval , 0.38 - 0.85 ; P = .006 ) . Both exercise programs prevented ADL disability ; the relative risks were 0.60 ( 95 % confidence interval , 0.38 - 0.97 ; P = .04 ) for resistance exercise and 0.53 ( 95 % confidence interval , 0.33 - 0.85 ; P = .009 ) for aerobic exercise . The lowest ADL disability risks were found for participants with the highest compliance to exercise . CONCLUSIONS Aerobic and resistance exercise may reduce the incidence of ADL disability in older persons with knee osteoarthritis .  Exercise may be an effective strategy for preventing ADL disability and , consequently , may prolong older persons ' autonomy CONTEXT Dementia is common , costly , and highly age related . Little attention has been paid to the identification of modifiable lifestyle habits for its prevention . OBJECTIVE To explore the association between physical activity and the risk of cognitive impairment and dementia .  DESIGN , SETTING , AND SUBJECTS Data come from a community sample of 9008 r and omly selected men and women 65 years or older , who were evaluated in the 1991 - 1992 Canadian Study of Health and Aging , a prospect i ve cohort study of dementia . Of the 6434 eligible subjects who were cognitively normal at baseline , 4615 completed a 5-year follow-up .  Screening and clinical evaluations were done at both waves of the study . In 1996 - 1997 , 3894 remained without cognitive impairment , 436 were diagnosed as having cognitive impairment-no dementia , and 285 were diagnosed as having dementia . MAIN OUTCOME MEASURE Incident cognitive impairment and dementia by levels of physical activity at baseline . RESULTS Compared with no exercise , physical activity was associated with lower risks of cognitive impairment , Alzheimer disease , and dementia of any type . Significant trends for increased protection with greater physical activity were observed . High levels of physical activity were associated with reduced risks of cognitive impairment ( age- , sex- , and education-adjusted odds ratio , 0.58 ; 95 % confidence interval , 0.41 - 0.83 ) , Alzheimer disease ( odds ratio , 0.50 ; 95 % confidence interval , 0.28 - 0.90 ) , and dementia of any type ( odds ratio , 0.63 ; 95 % confidence interval , 0.40 - 0.98 ) . CONCLUSION Regular physical activity could represent an important and potent protective factor for cognitive decline and dementia in elderly persons BACKGROUND To determine whether elevations of plasma norepinephrine ( NE ) in major depression represent increased sympathetic nervous system ( SNS ) activity and to assess the effects of desipramine hydrochloride on sympathetic function . METHODS SNS activity was assessed in depressed patients and controls by an isotope-dilution , plasma NE kinetic technique using mathematical modeling and compartmental analysis . This approach provided estimates of the rate of NE appearance into an extravascular compartment , which is the site of endogenous NE release from SNS nerves , the corresponding rate of NE appearance into plasma , and the rate of NE clearance from plasma . RESULTS Norepinephrine appearance into the extravascular and vascular compartments was significantly elevated in 17 depressed patients compared with that in 36 controls . The rate of NE clearance from plasma was similar in both groups . This is compatible with increased SNS activity in major depression . Desipramine , given for 2 days , significantly reduced the concentration of NE in plasma of patients and controls by markedly suppressing the rates of extravascular and vascular NE appearance , compatible with a short-term reduction in SNS activity . Desipramine prolonged the rate of NE clearance from plasma , consistent with a blockade of NE 
    Output:
    
Baseline depression may be a significant risk factor for development of sedentary lifestyle or decreased level of physical exercise .